FreeBSD/Linux Kernel Cross Reference
sys/ufs/ffs/ffs_softdep.c

     /*-
      * Copyright 1998, 2000 Marshall Kirk McKusick. All Rights Reserved.
      *
      * The soft updates code is derived from the appendix of a University
      * of Michigan technical report (Gregory R. Ganger and Yale N. Patt,
      * "Soft Updates: A Solution to the Metadata Update Problem in File
      * Systems", CSE-TR-254-95, August 1995).
      *
      * Further information about soft updates can be obtained from:
     *
     *      Marshall Kirk McKusick          http://www.mckusick.com/softdep/
     *      1614 Oxford Street              mckusick@mckusick.com
     *      Berkeley, CA 94709-1608         +1-510-843-9542
     *      USA
     *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     *
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY MARSHALL KIRK MCKUSICK ``AS IS'' AND ANY
     * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     * DISCLAIMED.  IN NO EVENT SHALL MARSHALL KIRK MCKUSICK BE LIABLE FOR
     * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      from: @(#)ffs_softdep.c 9.59 (McKusick) 6/21/00
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    /*
     * For now we want the safety net that the DEBUG flag provides.
     */
    #ifndef DEBUG
    #define DEBUG
    #endif
    
    #include <sys/param.h>
    #include <sys/kernel.h>
    #include <sys/systm.h>
    #include <sys/bio.h>
    #include <sys/buf.h>
    #include <sys/kdb.h>
    #include <sys/kthread.h>
    #include <sys/lock.h>
    #include <sys/malloc.h>
    #include <sys/mount.h>
    #include <sys/mutex.h>
    #include <sys/proc.h>
    #include <sys/stat.h>
    #include <sys/sysctl.h>
    #include <sys/syslog.h>
    #include <sys/vnode.h>
    #include <sys/conf.h>
    #include <ufs/ufs/dir.h>
    #include <ufs/ufs/extattr.h>
    #include <ufs/ufs/quota.h>
    #include <ufs/ufs/inode.h>
    #include <ufs/ufs/ufsmount.h>
    #include <ufs/ffs/fs.h>
    #include <ufs/ffs/softdep.h>
    #include <ufs/ffs/ffs_extern.h>
    #include <ufs/ufs/ufs_extern.h>
    
    #include <vm/vm.h>
    
    #include "opt_ffs.h"
    #include "opt_quota.h"
    
    #ifndef SOFTUPDATES
    
    int
    softdep_flushfiles(oldmnt, flags, td)
            struct mount *oldmnt;
            int flags;
            struct thread *td;
    {
    
            panic("softdep_flushfiles called");
    }
    
    int
    softdep_mount(devvp, mp, fs, cred)
            struct vnode *devvp;
            struct mount *mp;
            struct fs *fs;
           struct ucred *cred;
   {
   
           return (0);
   }
   
   void 
   softdep_initialize()
   {
   
           return;
   }
   
   void
   softdep_uninitialize()
   {
   
           return;
   }
   
   void
   softdep_setup_inomapdep(bp, ip, newinum)
           struct buf *bp;
           struct inode *ip;
           ino_t newinum;
   {
   
           panic("softdep_setup_inomapdep called");
   }
   
   void
   softdep_setup_blkmapdep(bp, mp, newblkno)
           struct buf *bp;
           struct mount *mp;
           ufs2_daddr_t newblkno;
   {
   
           panic("softdep_setup_blkmapdep called");
   }
   
   void 
   softdep_setup_allocdirect(ip, lbn, newblkno, oldblkno, newsize, oldsize, bp)
           struct inode *ip;
           ufs_lbn_t lbn;
           ufs2_daddr_t newblkno;
           ufs2_daddr_t oldblkno;
           long newsize;
           long oldsize;
           struct buf *bp;
   {
           
           panic("softdep_setup_allocdirect called");
   }
   
   void 
   softdep_setup_allocext(ip, lbn, newblkno, oldblkno, newsize, oldsize, bp)
           struct inode *ip;
           ufs_lbn_t lbn;
           ufs2_daddr_t newblkno;
           ufs2_daddr_t oldblkno;
           long newsize;
           long oldsize;
           struct buf *bp;
   {
           
           panic("softdep_setup_allocext called");
   }
   
   void
   softdep_setup_allocindir_page(ip, lbn, bp, ptrno, newblkno, oldblkno, nbp)
           struct inode *ip;
           ufs_lbn_t lbn;
           struct buf *bp;
           int ptrno;
           ufs2_daddr_t newblkno;
           ufs2_daddr_t oldblkno;
           struct buf *nbp;
   {
   
           panic("softdep_setup_allocindir_page called");
   }
   
   void
   softdep_setup_allocindir_meta(nbp, ip, bp, ptrno, newblkno)
           struct buf *nbp;
           struct inode *ip;
           struct buf *bp;
           int ptrno;
           ufs2_daddr_t newblkno;
   {
   
           panic("softdep_setup_allocindir_meta called");
   }
   
   void
   softdep_setup_freeblocks(ip, length, flags)
           struct inode *ip;
           off_t length;
           int flags;
   {
           
           panic("softdep_setup_freeblocks called");
   }
   
   void
   softdep_freefile(pvp, ino, mode)
                   struct vnode *pvp;
                   ino_t ino;
                   int mode;
   {
   
           panic("softdep_freefile called");
   }
   
   int 
   softdep_setup_directory_add(bp, dp, diroffset, newinum, newdirbp, isnewblk)
           struct buf *bp;
           struct inode *dp;
           off_t diroffset;
           ino_t newinum;
           struct buf *newdirbp;
           int isnewblk;
   {
   
           panic("softdep_setup_directory_add called");
   }
   
   void 
   softdep_change_directoryentry_offset(dp, base, oldloc, newloc, entrysize)
           struct inode *dp;
           caddr_t base;
           caddr_t oldloc;
           caddr_t newloc;
           int entrysize;
   {
   
           panic("softdep_change_directoryentry_offset called");
   }
   
   void 
   softdep_setup_remove(bp, dp, ip, isrmdir)
           struct buf *bp;
           struct inode *dp;
           struct inode *ip;
           int isrmdir;
   {
           
           panic("softdep_setup_remove called");
   }
   
   void 
   softdep_setup_directory_change(bp, dp, ip, newinum, isrmdir)
           struct buf *bp;
           struct inode *dp;
           struct inode *ip;
           ino_t newinum;
           int isrmdir;
   {
   
           panic("softdep_setup_directory_change called");
   }
   
   void
   softdep_change_linkcnt(ip)
           struct inode *ip;
   {
   
           panic("softdep_change_linkcnt called");
   }
   
   void 
   softdep_load_inodeblock(ip)
           struct inode *ip;
   {
   
           panic("softdep_load_inodeblock called");
   }
   
   void 
   softdep_update_inodeblock(ip, bp, waitfor)
           struct inode *ip;
           struct buf *bp;
           int waitfor;
   {
   
           panic("softdep_update_inodeblock called");
   }
   
   int
   softdep_fsync(vp)
           struct vnode *vp;       /* the "in_core" copy of the inode */
   {
   
           return (0);
   }
   
   void
   softdep_fsync_mountdev(vp)
           struct vnode *vp;
   {
   
           return;
   }
   
   int
   softdep_flushworklist(oldmnt, countp, td)
           struct mount *oldmnt;
           int *countp;
           struct thread *td;
   {
   
           *countp = 0;
           return (0);
   }
   
   int
   softdep_sync_metadata(struct vnode *vp)
   {
   
           return (0);
   }
   
   int
   softdep_slowdown(vp)
           struct vnode *vp;
   {
   
           panic("softdep_slowdown called");
   }
   
   void
   softdep_releasefile(ip)
           struct inode *ip;       /* inode with the zero effective link count */
   {
   
           panic("softdep_releasefile called");
   }
   
   int
   softdep_request_cleanup(fs, vp)
           struct fs *fs;
           struct vnode *vp;
   {
   
           return (0);
   }
   
   int
   softdep_check_suspend(struct mount *mp,
                         struct vnode *devvp,
                         int softdep_deps,
                         int softdep_accdeps,
                         int secondary_writes,
                         int secondary_accwrites)
   {
           struct bufobj *bo;
           int error;
           
           (void) softdep_deps,
           (void) softdep_accdeps;
   
           ASSERT_VI_LOCKED(devvp, "softdep_check_suspend");
           bo = &devvp->v_bufobj;
   
           for (;;) {
                   if (!MNT_ITRYLOCK(mp)) {
                           VI_UNLOCK(devvp);
                           MNT_ILOCK(mp);
                           MNT_IUNLOCK(mp);
                           VI_LOCK(devvp);
                           continue;
                   }
                   if (mp->mnt_secondary_writes != 0) {
                           VI_UNLOCK(devvp);
                           msleep(&mp->mnt_secondary_writes,
                                  MNT_MTX(mp),
                                  (PUSER - 1) | PDROP, "secwr", 0);
                           VI_LOCK(devvp);
                           continue;
                   }
                   break;
           }
   
           /*
            * Reasons for needing more work before suspend:
            * - Dirty buffers on devvp.
            * - Secondary writes occurred after start of vnode sync loop
            */
           error = 0;
           if (bo->bo_numoutput > 0 ||
               bo->bo_dirty.bv_cnt > 0 ||
               secondary_writes != 0 ||
               mp->mnt_secondary_writes != 0 ||
               secondary_accwrites != mp->mnt_secondary_accwrites)
                   error = EAGAIN;
           VI_UNLOCK(devvp);
           return (error);
   }
   
   void
   softdep_get_depcounts(struct mount *mp,
                         int *softdepactivep,
                         int *softdepactiveaccp)
   {
           (void) mp;
           *softdepactivep = 0;
           *softdepactiveaccp = 0;
   }
   
   #else
   /*
    * These definitions need to be adapted to the system to which
    * this file is being ported.
    */
   /*
    * malloc types defined for the softdep system.
    */
   static MALLOC_DEFINE(M_PAGEDEP, "pagedep","File page dependencies");
   static MALLOC_DEFINE(M_INODEDEP, "inodedep","Inode dependencies");
   static MALLOC_DEFINE(M_NEWBLK, "newblk","New block allocation");
   static MALLOC_DEFINE(M_BMSAFEMAP, "bmsafemap","Block or frag allocated from cyl group map");
   static MALLOC_DEFINE(M_ALLOCDIRECT, "allocdirect","Block or frag dependency for an inode");
   static MALLOC_DEFINE(M_INDIRDEP, "indirdep","Indirect block dependencies");
   static MALLOC_DEFINE(M_ALLOCINDIR, "allocindir","Block dependency for an indirect block");
   static MALLOC_DEFINE(M_FREEFRAG, "freefrag","Previously used frag for an inode");
   static MALLOC_DEFINE(M_FREEBLKS, "freeblks","Blocks freed from an inode");
   static MALLOC_DEFINE(M_FREEFILE, "freefile","Inode deallocated");
   static MALLOC_DEFINE(M_DIRADD, "diradd","New directory entry");
   static MALLOC_DEFINE(M_MKDIR, "mkdir","New directory");
   static MALLOC_DEFINE(M_DIRREM, "dirrem","Directory entry deleted");
   static MALLOC_DEFINE(M_NEWDIRBLK, "newdirblk","Unclaimed new directory block");
   static MALLOC_DEFINE(M_SAVEDINO, "savedino","Saved inodes");
   
   #define M_SOFTDEP_FLAGS (M_WAITOK | M_USE_RESERVE)
   
   #define D_PAGEDEP       0
   #define D_INODEDEP      1
   #define D_NEWBLK        2
   #define D_BMSAFEMAP     3
   #define D_ALLOCDIRECT   4
   #define D_INDIRDEP      5
   #define D_ALLOCINDIR    6
   #define D_FREEFRAG      7
   #define D_FREEBLKS      8
   #define D_FREEFILE      9
   #define D_DIRADD        10
   #define D_MKDIR         11
   #define D_DIRREM        12
   #define D_NEWDIRBLK     13
   #define D_LAST          D_NEWDIRBLK
   
   /* 
    * translate from workitem type to memory type
    * MUST match the defines above, such that memtype[D_XXX] == M_XXX
    */
   static struct malloc_type *memtype[] = {
           M_PAGEDEP,
           M_INODEDEP,
           M_NEWBLK,
           M_BMSAFEMAP,
           M_ALLOCDIRECT,
           M_INDIRDEP,
           M_ALLOCINDIR,
           M_FREEFRAG,
           M_FREEBLKS,
           M_FREEFILE,
           M_DIRADD,
           M_MKDIR,
           M_DIRREM,
           M_NEWDIRBLK
   };
   
   #define DtoM(type) (memtype[type])
   
   /*
    * Names of malloc types.
    */
   #define TYPENAME(type)  \
           ((unsigned)(type) < D_LAST ? memtype[type]->ks_shortdesc : "???")
   /*
    * End system adaptation definitions.
    */
   
   /*
    * Forward declarations.
    */
   struct inodedep_hashhead;
   struct newblk_hashhead;
   struct pagedep_hashhead;
   
   /*
    * Internal function prototypes.
    */
   static  void softdep_error(char *, int);
   static  void drain_output(struct vnode *);
   static  struct buf *getdirtybuf(struct buf *, struct mtx *, int);
   static  void clear_remove(struct thread *);
   static  void clear_inodedeps(struct thread *);
   static  int flush_pagedep_deps(struct vnode *, struct mount *,
               struct diraddhd *);
   static  int flush_inodedep_deps(struct mount *, ino_t);
   static  int flush_deplist(struct allocdirectlst *, int, int *);
   static  int handle_written_filepage(struct pagedep *, struct buf *);
   static  void diradd_inode_written(struct diradd *, struct inodedep *);
   static  int handle_written_inodeblock(struct inodedep *, struct buf *);
   static  void handle_allocdirect_partdone(struct allocdirect *);
   static  void handle_allocindir_partdone(struct allocindir *);
   static  void initiate_write_filepage(struct pagedep *, struct buf *);
   static  void handle_written_mkdir(struct mkdir *, int);
   static  void initiate_write_inodeblock_ufs1(struct inodedep *, struct buf *);
   static  void initiate_write_inodeblock_ufs2(struct inodedep *, struct buf *);
   static  void handle_workitem_freefile(struct freefile *);
   static  void handle_workitem_remove(struct dirrem *, struct vnode *);
   static  struct dirrem *newdirrem(struct buf *, struct inode *,
               struct inode *, int, struct dirrem **);
   static  void free_diradd(struct diradd *);
   static  void free_allocindir(struct allocindir *, struct inodedep *);
   static  void free_newdirblk(struct newdirblk *);
   static  int indir_trunc(struct freeblks *, ufs2_daddr_t, int, ufs_lbn_t,
               ufs2_daddr_t *);
   static  void deallocate_dependencies(struct buf *, struct inodedep *);
   static  void free_allocdirect(struct allocdirectlst *,
               struct allocdirect *, int);
   static  int check_inode_unwritten(struct inodedep *);
   static  int free_inodedep(struct inodedep *);
   static  void handle_workitem_freeblocks(struct freeblks *, int);
   static  void merge_inode_lists(struct allocdirectlst *,struct allocdirectlst *);
   static  void setup_allocindir_phase2(struct buf *, struct inode *,
               struct allocindir *);
   static  struct allocindir *newallocindir(struct inode *, int, ufs2_daddr_t,
               ufs2_daddr_t);
   static  void handle_workitem_freefrag(struct freefrag *);
   static  struct freefrag *newfreefrag(struct inode *, ufs2_daddr_t, long);
   static  void allocdirect_merge(struct allocdirectlst *,
               struct allocdirect *, struct allocdirect *);
   static  struct bmsafemap *bmsafemap_lookup(struct mount *, struct buf *);
   static  int newblk_find(struct newblk_hashhead *, struct fs *, ufs2_daddr_t,
               struct newblk **);
   static  int newblk_lookup(struct fs *, ufs2_daddr_t, int, struct newblk **);
   static  int inodedep_find(struct inodedep_hashhead *, struct fs *, ino_t,
               struct inodedep **);
   static  int inodedep_lookup(struct mount *, ino_t, int, struct inodedep **);
   static  int pagedep_lookup(struct inode *, ufs_lbn_t, int, struct pagedep **);
   static  int pagedep_find(struct pagedep_hashhead *, ino_t, ufs_lbn_t,
               struct mount *mp, int, struct pagedep **);
   static  void pause_timer(void *);
   static  int request_cleanup(struct mount *, int);
   static  int process_worklist_item(struct mount *, int);
   static  void add_to_worklist(struct worklist *);
   static  void softdep_flush(void);
   static  int softdep_speedup(void);
   
   /*
    * Exported softdep operations.
    */
   static  void softdep_disk_io_initiation(struct buf *);
   static  void softdep_disk_write_complete(struct buf *);
   static  void softdep_deallocate_dependencies(struct buf *);
   static  int softdep_count_dependencies(struct buf *bp, int);
   
   static struct mtx lk;
   MTX_SYSINIT(softdep_lock, &lk, "Softdep Lock", MTX_DEF);
   
   #define TRY_ACQUIRE_LOCK(lk)            mtx_trylock(lk)
   #define ACQUIRE_LOCK(lk)                mtx_lock(lk)
   #define FREE_LOCK(lk)                   mtx_unlock(lk)
   
   /*
    * Worklist queue management.
    * These routines require that the lock be held.
    */
   #ifndef /* NOT */ DEBUG
   #define WORKLIST_INSERT(head, item) do {        \
           (item)->wk_state |= ONWORKLIST;         \
           LIST_INSERT_HEAD(head, item, wk_list);  \
   } while (0)
   #define WORKLIST_REMOVE(item) do {              \
           (item)->wk_state &= ~ONWORKLIST;        \
           LIST_REMOVE(item, wk_list);             \
   } while (0)
   #else /* DEBUG */
   static  void worklist_insert(struct workhead *, struct worklist *);
   static  void worklist_remove(struct worklist *);
   
   #define WORKLIST_INSERT(head, item) worklist_insert(head, item)
   #define WORKLIST_REMOVE(item) worklist_remove(item)
   
   static void
   worklist_insert(head, item)
           struct workhead *head;
           struct worklist *item;
   {
   
           mtx_assert(&lk, MA_OWNED);
           if (item->wk_state & ONWORKLIST)
                   panic("worklist_insert: already on list");
           item->wk_state |= ONWORKLIST;
           LIST_INSERT_HEAD(head, item, wk_list);
   }
   
   static void
   worklist_remove(item)
           struct worklist *item;
   {
   
           mtx_assert(&lk, MA_OWNED);
           if ((item->wk_state & ONWORKLIST) == 0)
                   panic("worklist_remove: not on list");
           item->wk_state &= ~ONWORKLIST;
           LIST_REMOVE(item, wk_list);
   }
   #endif /* DEBUG */
   
   /*
    * Routines for tracking and managing workitems.
    */
   static  void workitem_free(struct worklist *, int);
   static  void workitem_alloc(struct worklist *, int, struct mount *);
   
   #define WORKITEM_FREE(item, type) workitem_free((struct worklist *)(item), (type))
   
   static void
   workitem_free(item, type)
           struct worklist *item;
           int type;
   {
           struct ufsmount *ump;
           mtx_assert(&lk, MA_OWNED);
   
   #ifdef DEBUG
           if (item->wk_state & ONWORKLIST)
                   panic("workitem_free: still on list");
           if (item->wk_type != type)
                   panic("workitem_free: type mismatch");
   #endif
           ump = VFSTOUFS(item->wk_mp);
           if (--ump->softdep_deps == 0 && ump->softdep_req)
                   wakeup(&ump->softdep_deps);
           FREE(item, DtoM(type));
   }
   
   static void
   workitem_alloc(item, type, mp)
           struct worklist *item;
           int type;
           struct mount *mp;
   {
           item->wk_type = type;
           item->wk_mp = mp;
           item->wk_state = 0;
           ACQUIRE_LOCK(&lk);
           VFSTOUFS(mp)->softdep_deps++;
           VFSTOUFS(mp)->softdep_accdeps++;
           FREE_LOCK(&lk);
   }
   
   /*
    * Workitem queue management
    */
   static int max_softdeps;        /* maximum number of structs before slowdown */
   static int maxindirdeps = 50;   /* max number of indirdeps before slowdown */
   static int tickdelay = 2;       /* number of ticks to pause during slowdown */
   static int proc_waiting;        /* tracks whether we have a timeout posted */
   static int *stat_countp;        /* statistic to count in proc_waiting timeout */
   static struct callout_handle handle; /* handle on posted proc_waiting timeout */
   static int req_pending;
   static int req_clear_inodedeps; /* syncer process flush some inodedeps */
   #define FLUSH_INODES            1
   static int req_clear_remove;    /* syncer process flush some freeblks */
   #define FLUSH_REMOVE            2
   #define FLUSH_REMOVE_WAIT       3
   static long num_freeblkdep;     /* number of freeblks workitems allocated */
   
   /*
    * runtime statistics
    */
   static int stat_worklist_push;  /* number of worklist cleanups */
   static int stat_blk_limit_push; /* number of times block limit neared */
   static int stat_ino_limit_push; /* number of times inode limit neared */
   static int stat_blk_limit_hit;  /* number of times block slowdown imposed */
   static int stat_ino_limit_hit;  /* number of times inode slowdown imposed */
   static int stat_sync_limit_hit; /* number of synchronous slowdowns imposed */
   static int stat_indir_blk_ptrs; /* bufs redirtied as indir ptrs not written */
   static int stat_inode_bitmap;   /* bufs redirtied as inode bitmap not written */
   static int stat_direct_blk_ptrs;/* bufs redirtied as direct ptrs not written */
   static int stat_dir_entry;      /* bufs redirtied as dir entry cannot write */
   
   SYSCTL_INT(_debug, OID_AUTO, max_softdeps, CTLFLAG_RW, &max_softdeps, 0, "");
   SYSCTL_INT(_debug, OID_AUTO, tickdelay, CTLFLAG_RW, &tickdelay, 0, "");
   SYSCTL_INT(_debug, OID_AUTO, maxindirdeps, CTLFLAG_RW, &maxindirdeps, 0, "");
   SYSCTL_INT(_debug, OID_AUTO, worklist_push, CTLFLAG_RW, &stat_worklist_push, 0,"");
   SYSCTL_INT(_debug, OID_AUTO, blk_limit_push, CTLFLAG_RW, &stat_blk_limit_push, 0,"");
   SYSCTL_INT(_debug, OID_AUTO, ino_limit_push, CTLFLAG_RW, &stat_ino_limit_push, 0,"");
   SYSCTL_INT(_debug, OID_AUTO, blk_limit_hit, CTLFLAG_RW, &stat_blk_limit_hit, 0, "");
   SYSCTL_INT(_debug, OID_AUTO, ino_limit_hit, CTLFLAG_RW, &stat_ino_limit_hit, 0, "");
   SYSCTL_INT(_debug, OID_AUTO, sync_limit_hit, CTLFLAG_RW, &stat_sync_limit_hit, 0, "");
   SYSCTL_INT(_debug, OID_AUTO, indir_blk_ptrs, CTLFLAG_RW, &stat_indir_blk_ptrs, 0, "");
   SYSCTL_INT(_debug, OID_AUTO, inode_bitmap, CTLFLAG_RW, &stat_inode_bitmap, 0, "");
   SYSCTL_INT(_debug, OID_AUTO, direct_blk_ptrs, CTLFLAG_RW, &stat_direct_blk_ptrs, 0, "");
   SYSCTL_INT(_debug, OID_AUTO, dir_entry, CTLFLAG_RW, &stat_dir_entry, 0, "");
   /* SYSCTL_INT(_debug, OID_AUTO, worklist_num, CTLFLAG_RD, &softdep_on_worklist, 0, ""); */
   
   SYSCTL_DECL(_vfs_ffs);
   
   static int compute_summary_at_mount = 0;        /* Whether to recompute the summary at mount time */
   SYSCTL_INT(_vfs_ffs, OID_AUTO, compute_summary_at_mount, CTLFLAG_RW,
              &compute_summary_at_mount, 0, "Recompute summary at mount");
   
   static struct proc *softdepproc;
   static struct kproc_desc softdep_kp = {
           "softdepflush",
           softdep_flush,
           &softdepproc
   };
   SYSINIT(sdproc, SI_SUB_KTHREAD_UPDATE, SI_ORDER_ANY, kproc_start, &softdep_kp)
   
   static void
   softdep_flush(void)
   {
           struct mount *nmp;
           struct mount *mp;
           struct ufsmount *ump;
           struct thread *td;
           int remaining;
           int vfslocked;
   
           td = curthread;
           td->td_pflags |= TDP_NORUNNINGBUF;
   
           for (;;) {      
                   kthread_suspend_check(softdepproc);
                   vfslocked = VFS_LOCK_GIANT((struct mount *)NULL);
                   ACQUIRE_LOCK(&lk);
                   /*
                    * If requested, try removing inode or removal dependencies.
                    */
                   if (req_clear_inodedeps) {
                           clear_inodedeps(td);
                           req_clear_inodedeps -= 1;
                           wakeup_one(&proc_waiting);
                   }
                   if (req_clear_remove) {
                           clear_remove(td);
                           req_clear_remove -= 1;
                           wakeup_one(&proc_waiting);
                   }
                   FREE_LOCK(&lk);
                   VFS_UNLOCK_GIANT(vfslocked);
                   remaining = 0;
                   mtx_lock(&mountlist_mtx);
                   for (mp = TAILQ_FIRST(&mountlist); mp != NULL; mp = nmp)  {
                           nmp = TAILQ_NEXT(mp, mnt_list);
                           if ((mp->mnt_flag & MNT_SOFTDEP) == 0)
                                   continue;
                           if (vfs_busy(mp, LK_NOWAIT, &mountlist_mtx, td))
                                   continue;
                           vfslocked = VFS_LOCK_GIANT(mp);
                           softdep_process_worklist(mp, 0);
                           ump = VFSTOUFS(mp);
                           remaining += ump->softdep_on_worklist -
                                   ump->softdep_on_worklist_inprogress;
                           VFS_UNLOCK_GIANT(vfslocked);
                           mtx_lock(&mountlist_mtx);
                           nmp = TAILQ_NEXT(mp, mnt_list);
                           vfs_unbusy(mp, td);
                   }
                   mtx_unlock(&mountlist_mtx);
                   if (remaining)
                           continue;
                   ACQUIRE_LOCK(&lk);
                   if (!req_pending)
                           msleep(&req_pending, &lk, PVM, "sdflush", hz);
                   req_pending = 0;
                   FREE_LOCK(&lk);
           }
   }
   
   static int
   softdep_speedup(void)
   {
   
           mtx_assert(&lk, MA_OWNED);
           if (req_pending == 0) {
                   req_pending = 1;
                   wakeup(&req_pending);
           }
   
           return speedup_syncer();
   }
   
   /*
    * Add an item to the end of the work queue.
    * This routine requires that the lock be held.
    * This is the only routine that adds items to the list.
    * The following routine is the only one that removes items
    * and does so in order from first to last.
    */
   static void
   add_to_worklist(wk)
           struct worklist *wk;
   {
           struct ufsmount *ump;
   
           mtx_assert(&lk, MA_OWNED);
           ump = VFSTOUFS(wk->wk_mp);
           if (wk->wk_state & ONWORKLIST)
                   panic("add_to_worklist: already on list");
           wk->wk_state |= ONWORKLIST;
           if (LIST_EMPTY(&ump->softdep_workitem_pending))
                   LIST_INSERT_HEAD(&ump->softdep_workitem_pending, wk, wk_list);
           else
                   LIST_INSERT_AFTER(ump->softdep_worklist_tail, wk, wk_list);
           ump->softdep_worklist_tail = wk;
           ump->softdep_on_worklist += 1;
   }
   
   /*
    * Process that runs once per second to handle items in the background queue.
    *
    * Note that we ensure that everything is done in the order in which they
    * appear in the queue. The code below depends on this property to ensure
    * that blocks of a file are freed before the inode itself is freed. This
    * ordering ensures that no new <vfsid, inum, lbn> triples will be generated
    * until all the old ones have been purged from the dependency lists.
    */
   int 
   softdep_process_worklist(mp, full)
           struct mount *mp;
           int full;
   {
           struct thread *td = curthread;
           int cnt, matchcnt, loopcount;
           struct ufsmount *ump;
           long starttime;
   
           KASSERT(mp != NULL, ("softdep_process_worklist: NULL mp"));
           /*
            * Record the process identifier of our caller so that we can give
            * this process preferential treatment in request_cleanup below.
            */
           matchcnt = 0;
           ump = VFSTOUFS(mp);
           ACQUIRE_LOCK(&lk);
           loopcount = 1;
           starttime = time_second;
           while (ump->softdep_on_worklist > 0) {
                   if ((cnt = process_worklist_item(mp, 0)) == -1)
                           break;
                   else
                           matchcnt += cnt;
                   /*
                    * If requested, try removing inode or removal dependencies.
                    */
                   if (req_clear_inodedeps) {
                           clear_inodedeps(td);
                           req_clear_inodedeps -= 1;
                           wakeup_one(&proc_waiting);
                   }
                   if (req_clear_remove) {
                           clear_remove(td);
                           req_clear_remove -= 1;
                           wakeup_one(&proc_waiting);
                   }
                   /*
                    * We do not generally want to stop for buffer space, but if
                    * we are really being a buffer hog, we will stop and wait.
                    */
                   if (loopcount++ % 128 == 0) {
                           FREE_LOCK(&lk);
                           bwillwrite();
                           ACQUIRE_LOCK(&lk);
                   }
                   /*
                    * Never allow processing to run for more than one
                    * second. Otherwise the other mountpoints may get
                    * excessively backlogged.
                    */
                   if (!full && starttime != time_second) {
                           matchcnt = -1;
                           break;
                   }
           }
           FREE_LOCK(&lk);
           return (matchcnt);
   }
   
   /*
    * Process one item on the worklist.
    */
   static int
   process_worklist_item(mp, flags)
           struct mount *mp;
           int flags;
   {
           struct worklist *wk, *wkend;
           struct ufsmount *ump;
           struct vnode *vp;
           int matchcnt = 0;
   
           mtx_assert(&lk, MA_OWNED);
           KASSERT(mp != NULL, ("process_worklist_item: NULL mp"));
           /*
            * If we are being called because of a process doing a
            * copy-on-write, then it is not safe to write as we may
            * recurse into the copy-on-write routine.
            */
           if (curthread->td_pflags & TDP_COWINPROGRESS)
                   return (-1);
           /*
            * Normally we just process each item on the worklist in order.
            * However, if we are in a situation where we cannot lock any
            * inodes, we have to skip over any dirrem requests whose
            * vnodes are resident and locked.
            */
           ump = VFSTOUFS(mp);
           vp = NULL;
           LIST_FOREACH(wk, &ump->softdep_workitem_pending, wk_list) {
                   if (wk->wk_state & INPROGRESS)
                           continue;
                   if ((flags & LK_NOWAIT) == 0 || wk->wk_type != D_DIRREM)
                           break;
                   wk->wk_state |= INPROGRESS;
                   ump->softdep_on_worklist_inprogress++;
                   FREE_LOCK(&lk);
                   ffs_vget(mp, WK_DIRREM(wk)->dm_oldinum,
                       LK_NOWAIT | LK_EXCLUSIVE, &vp);
                   ACQUIRE_LOCK(&lk);
                   wk->wk_state &= ~INPROGRESS;
                   ump->softdep_on_worklist_inprogress--;
                   if (vp != NULL)
                           break;
           }
           if (wk == 0)
                   return (-1);
           /*
            * Remove the item to be processed. If we are removing the last
            * item on the list, we need to recalculate the tail pointer.
            * As this happens rarely and usually when the list is short,
            * we just run down the list to find it rather than tracking it
            * in the above loop.
            */
           WORKLIST_REMOVE(wk);
           if (wk == ump->softdep_worklist_tail) {
                   LIST_FOREACH(wkend, &ump->softdep_workitem_pending, wk_list)
                           if (LIST_NEXT(wkend, wk_list) == NULL)
                                   break;
                   ump->softdep_worklist_tail = wkend;
           }
           ump->softdep_on_worklist -= 1;
           FREE_LOCK(&lk);
           if (vn_start_secondary_write(NULL, &mp, V_NOWAIT))
                   panic("process_worklist_item: suspended filesystem");
           matchcnt++;
           switch (wk->wk_type) {
   
           case D_DIRREM:
                   /* removal of a directory entry */
                   handle_workitem_remove(WK_DIRREM(wk), vp);
                   break;
   
           case D_FREEBLKS:
                   /* releasing blocks and/or fragments from a file */
                   handle_workitem_freeblocks(WK_FREEBLKS(wk), flags & LK_NOWAIT);
                   break;
   
           case D_FREEFRAG:
                   /* releasing a fragment when replaced as a file grows */
                   handle_workitem_freefrag(WK_FREEFRAG(wk));
                   break;
   
           case D_FREEFILE:
                   /* releasing an inode when its link count drops to 0 */
                   handle_workitem_freefile(WK_FREEFILE(wk));
                   break;
   
           default:
                   panic("%s_process_worklist: Unknown type %s",
                       "softdep", TYPENAME(wk->wk_type));
                   /* NOTREACHED */
           }
           vn_finished_secondary_write(mp);
           ACQUIRE_LOCK(&lk);
           return (matchcnt);
   }
   
   /*
    * Move dependencies from one buffer to another.
    */
   void
   softdep_move_dependencies(oldbp, newbp)
           struct buf *oldbp;
           struct buf *newbp;
   {
           struct worklist *wk, *wktail;
   
           if (!LIST_EMPTY(&newbp->b_dep))
                   panic("softdep_move_dependencies: need merge code");
           wktail = 0;
           ACQUIRE_LOCK(&lk);
           while ((wk = LIST_FIRST(&oldbp->b_dep)) != NULL) {
                  LIST_REMOVE(wk, wk_list);
                  if (wktail == 0)
                          LIST_INSERT_HEAD(&newbp->b_dep, wk, wk_list);
                  else
                          LIST_INSERT_AFTER(wktail, wk, wk_list);
                  wktail = wk;
          }
          FREE_LOCK(&lk);
  }
  
  /*
   * Purge the work list of all items associated with a particular mount point.
   */
  int
  softdep_flushworklist(oldmnt, countp, td)
          struct mount *oldmnt;
          int *countp;
          struct thread *td;
  {
          struct vnode *devvp;
          int count, error = 0;
          struct ufsmount *ump;
  
          /*
           * Alternately flush the block device associated with the mount
           * point and process any dependencies that the flushing
           * creates. We continue until no more worklist dependencies
           * are found.
           */
          *countp = 0;
          ump = VFSTOUFS(oldmnt);
          devvp = ump->um_devvp;
          while ((count = softdep_process_worklist(oldmnt, 1)) > 0) {
                  *countp += count;
                  vn_lock(devvp, LK_EXCLUSIVE | LK_RETRY, td);
                  error = VOP_FSYNC(devvp, MNT_WAIT, td);
                  VOP_UNLOCK(devvp, 0, td);
                  if (error)
                          break;
          }
          return (error);
  }
  
  int
  softdep_waitidle(struct mount *mp)
  {
          struct ufsmount *ump;
          int error;
          int i;
  
          ump = VFSTOUFS(mp);
          ACQUIRE_LOCK(&lk);
          for (i = 0; i < 10 && ump->softdep_deps; i++) {
                  ump->softdep_req = 1;
                  if (ump->softdep_on_worklist)
                          panic("softdep_waitidle: work added after flush.");
                  msleep(&ump->softdep_deps, &lk, PVM, "softdeps", 1);
          }
          ump->softdep_req = 0;
          FREE_LOCK(&lk);
          error = 0;
          if (i == 10) {
                  error = EBUSY;
                  printf("softdep_waitidle: Failed to flush worklist for %p\n",
                      mp);
          }
  
          return (error);
  }
  
  /*
   * Flush all vnodes and worklist items associated with a specified mount point.
   */
  int
  softdep_flushfiles(oldmnt, flags, td)
          struct mount *oldmnt;
          int flags;
          struct thread *td;
  {
          int error, count, loopcnt;
  
          error = 0;
  
          /*
           * Alternately flush the vnodes associated with the mount
           * point and process any dependencies that the flushing
           * creates. In theory, this loop can happen at most twice,
           * but we give it a few extra just to be sure.
           */
          for (loopcnt = 10; loopcnt > 0; loopcnt--) {
                  /*
                   * Do another flush in case any vnodes were brought in
                   * as part of the cleanup operations.
                   */
                  if ((error = ffs_flushfiles(oldmnt, flags, td)) != 0)
                          break;
                  if ((error = softdep_flushworklist(oldmnt, &count, td)) != 0 ||
                      count == 0)
                          break;
          }
          /*
           * If we are unmounting then it is an error to fail. If we
           * are simply trying to downgrade to read-only, then filesystem
           * activity can keep us busy forever, so we just fail with EBUSY.
           */
          if (loopcnt == 0) {
                  if (oldmnt->mnt_kern_flag & MNTK_UNMOUNT)
                          panic("softdep_flushfiles: looping");
                  error = EBUSY;
          }
          if (!error)
                  error = softdep_waitidle(oldmnt);
          return (error);
  }
  
  /*
   * Structure hashing.
   * 
   * There are three types of structures that can be looked up:
   *      1) pagedep structures identified by mount point, inode number,
   *         and logical block.
   *      2) inodedep structures identified by mount point and inode number.
   *      3) newblk structures identified by mount point and
   *         physical block number.
   *
   * The "pagedep" and "inodedep" dependency structures are hashed
   * separately from the file blocks and inodes to which they correspond.
   * This separation helps when the in-memory copy of an inode or
   * file block must be replaced. It also obviates the need to access
   * an inode or file page when simply updating (or de-allocating)
   * dependency structures. Lookup of newblk structures is needed to
   * find newly allocated blocks when trying to associate them with
   * their allocdirect or allocindir structure.
   *
   * The lookup routines optionally create and hash a new instance when
   * an existing entry is not found.
   */
  #define DEPALLOC        0x0001  /* allocate structure if lookup fails */
  #define NODELAY         0x0002  /* cannot do background work */
  
  /*
   * Structures and routines associated with pagedep caching.
   */
  LIST_HEAD(pagedep_hashhead, pagedep) *pagedep_hashtbl;
  u_long  pagedep_hash;           /* size of hash table - 1 */
  #define PAGEDEP_HASH(mp, inum, lbn) \
          (&pagedep_hashtbl[((((register_t)(mp)) >> 13) + (inum) + (lbn)) & \
              pagedep_hash])
  
  static int
  pagedep_find(pagedephd, ino, lbn, mp, flags, pagedeppp)
          struct pagedep_hashhead *pagedephd;
          ino_t ino;
          ufs_lbn_t lbn;
          struct mount *mp;
          int flags;
          struct pagedep **pagedeppp;
  {
          struct pagedep *pagedep;
  
          LIST_FOREACH(pagedep, pagedephd, pd_hash)
                  if (ino == pagedep->pd_ino &&
                      lbn == pagedep->pd_lbn &&
                      mp == pagedep->pd_list.wk_mp)
                          break;
          if (pagedep) {
                  *pagedeppp = pagedep;
                  if ((flags & DEPALLOC) != 0 &&
                      (pagedep->pd_state & ONWORKLIST) == 0)
                          return (0);
                  return (1);
          }
          *pagedeppp = NULL;
          return (0);
  }
  /*
   * Look up a pagedep. Return 1 if found, 0 if not found or found
   * when asked to allocate but not associated with any buffer.
   * If not found, allocate if DEPALLOC flag is passed.
   * Found or allocated entry is returned in pagedeppp.
   * This routine must be called with splbio interrupts blocked.
   */
  static int
  pagedep_lookup(ip, lbn, flags, pagedeppp)
          struct inode *ip;
          ufs_lbn_t lbn;
          int flags;
          struct pagedep **pagedeppp;
  {
          struct pagedep *pagedep;
          struct pagedep_hashhead *pagedephd;
          struct mount *mp;
          int ret;
          int i;
  
          mtx_assert(&lk, MA_OWNED);
          mp = ITOV(ip)->v_mount;
          pagedephd = PAGEDEP_HASH(mp, ip->i_number, lbn);
  
          ret = pagedep_find(pagedephd, ip->i_number, lbn, mp, flags, pagedeppp);
          if (*pagedeppp || (flags & DEPALLOC) == 0)
                  return (ret);
          FREE_LOCK(&lk);
          MALLOC(pagedep, struct pagedep *, sizeof(struct pagedep),
              M_PAGEDEP, M_SOFTDEP_FLAGS|M_ZERO);
          workitem_alloc(&pagedep->pd_list, D_PAGEDEP, mp);
          ACQUIRE_LOCK(&lk);
          ret = pagedep_find(pagedephd, ip->i_number, lbn, mp, flags, pagedeppp);
          if (*pagedeppp) {
                  WORKITEM_FREE(pagedep, D_PAGEDEP);
                  return (ret);
          }
          pagedep->pd_ino = ip->i_number;
          pagedep->pd_lbn = lbn;
          LIST_INIT(&pagedep->pd_dirremhd);
          LIST_INIT(&pagedep->pd_pendinghd);
          for (i = 0; i < DAHASHSZ; i++)
                  LIST_INIT(&pagedep->pd_diraddhd[i]);
          LIST_INSERT_HEAD(pagedephd, pagedep, pd_hash);
          *pagedeppp = pagedep;
          return (0);
  }
  
  /*
   * Structures and routines associated with inodedep caching.
   */
  LIST_HEAD(inodedep_hashhead, inodedep) *inodedep_hashtbl;
  static u_long   inodedep_hash;  /* size of hash table - 1 */
  static long     num_inodedep;   /* number of inodedep allocated */
  #define INODEDEP_HASH(fs, inum) \
        (&inodedep_hashtbl[((((register_t)(fs)) >> 13) + (inum)) & inodedep_hash])
  
  static int
  inodedep_find(inodedephd, fs, inum, inodedeppp)
          struct inodedep_hashhead *inodedephd;
          struct fs *fs;
          ino_t inum;
          struct inodedep **inodedeppp;
  {
          struct inodedep *inodedep;
  
          LIST_FOREACH(inodedep, inodedephd, id_hash)
                  if (inum == inodedep->id_ino && fs == inodedep->id_fs)
                          break;
          if (inodedep) {
                  *inodedeppp = inodedep;
                  return (1);
          }
          *inodedeppp = NULL;
  
          return (0);
  }
  /*
   * Look up an inodedep. Return 1 if found, 0 if not found.
   * If not found, allocate if DEPALLOC flag is passed.
   * Found or allocated entry is returned in inodedeppp.
   * This routine must be called with splbio interrupts blocked.
   */
  static int
  inodedep_lookup(mp, inum, flags, inodedeppp)
          struct mount *mp;
          ino_t inum;
          int flags;
          struct inodedep **inodedeppp;
  {
          struct inodedep *inodedep;
          struct inodedep_hashhead *inodedephd;
          struct fs *fs;
  
          mtx_assert(&lk, MA_OWNED);
          fs = VFSTOUFS(mp)->um_fs;
          inodedephd = INODEDEP_HASH(fs, inum);
  
          if (inodedep_find(inodedephd, fs, inum, inodedeppp))
                  return (1);
          if ((flags & DEPALLOC) == 0)
                  return (0);
          /*
           * If we are over our limit, try to improve the situation.
           */
          if (num_inodedep > max_softdeps && (flags & NODELAY) == 0)
                  request_cleanup(mp, FLUSH_INODES);
          FREE_LOCK(&lk);
          MALLOC(inodedep, struct inodedep *, sizeof(struct inodedep),
                  M_INODEDEP, M_SOFTDEP_FLAGS);
          workitem_alloc(&inodedep->id_list, D_INODEDEP, mp);
          ACQUIRE_LOCK(&lk);
          if (inodedep_find(inodedephd, fs, inum, inodedeppp)) {
                  WORKITEM_FREE(inodedep, D_INODEDEP);
                  return (1);
          }
          num_inodedep += 1;
          inodedep->id_fs = fs;
          inodedep->id_ino = inum;
          inodedep->id_state = ALLCOMPLETE;
          inodedep->id_nlinkdelta = 0;
          inodedep->id_savedino1 = NULL;
          inodedep->id_savedsize = -1;
          inodedep->id_savedextsize = -1;
          inodedep->id_buf = NULL;
          LIST_INIT(&inodedep->id_pendinghd);
          LIST_INIT(&inodedep->id_inowait);
          LIST_INIT(&inodedep->id_bufwait);
          TAILQ_INIT(&inodedep->id_inoupdt);
          TAILQ_INIT(&inodedep->id_newinoupdt);
          TAILQ_INIT(&inodedep->id_extupdt);
          TAILQ_INIT(&inodedep->id_newextupdt);
          LIST_INSERT_HEAD(inodedephd, inodedep, id_hash);
          *inodedeppp = inodedep;
          return (0);
  }
  
  /*
   * Structures and routines associated with newblk caching.
   */
  LIST_HEAD(newblk_hashhead, newblk) *newblk_hashtbl;
  u_long  newblk_hash;            /* size of hash table - 1 */
  #define NEWBLK_HASH(fs, inum) \
          (&newblk_hashtbl[((((register_t)(fs)) >> 13) + (inum)) & newblk_hash])
  
  static int
  newblk_find(newblkhd, fs, newblkno, newblkpp)
          struct newblk_hashhead *newblkhd;
          struct fs *fs;
          ufs2_daddr_t newblkno;
          struct newblk **newblkpp;
  {
          struct newblk *newblk;
  
          LIST_FOREACH(newblk, newblkhd, nb_hash)
                  if (newblkno == newblk->nb_newblkno && fs == newblk->nb_fs)
                          break;
          if (newblk) {
                  *newblkpp = newblk;
                  return (1);
          }
          *newblkpp = NULL;
          return (0);
  }
  
  /*
   * Look up a newblk. Return 1 if found, 0 if not found.
   * If not found, allocate if DEPALLOC flag is passed.
   * Found or allocated entry is returned in newblkpp.
   */
  static int
  newblk_lookup(fs, newblkno, flags, newblkpp)
          struct fs *fs;
          ufs2_daddr_t newblkno;
          int flags;
          struct newblk **newblkpp;
  {
          struct newblk *newblk;
          struct newblk_hashhead *newblkhd;
  
          newblkhd = NEWBLK_HASH(fs, newblkno);
          if (newblk_find(newblkhd, fs, newblkno, newblkpp))
                  return (1);
          if ((flags & DEPALLOC) == 0)
                  return (0);
          FREE_LOCK(&lk);
          MALLOC(newblk, struct newblk *, sizeof(struct newblk),
                  M_NEWBLK, M_SOFTDEP_FLAGS);
          ACQUIRE_LOCK(&lk);
          if (newblk_find(newblkhd, fs, newblkno, newblkpp)) {
                  FREE(newblk, M_NEWBLK);
                  return (1);
          }
          newblk->nb_state = 0;
          newblk->nb_fs = fs;
          newblk->nb_newblkno = newblkno;
          LIST_INSERT_HEAD(newblkhd, newblk, nb_hash);
          *newblkpp = newblk;
          return (0);
  }
  
  /*
   * Executed during filesystem system initialization before
   * mounting any filesystems.
   */
  void 
  softdep_initialize()
  {
  
          LIST_INIT(&mkdirlisthd);
          max_softdeps = desiredvnodes * 4;
          pagedep_hashtbl = hashinit(desiredvnodes / 5, M_PAGEDEP,
              &pagedep_hash);
          inodedep_hashtbl = hashinit(desiredvnodes, M_INODEDEP, &inodedep_hash);
          newblk_hashtbl = hashinit(64, M_NEWBLK, &newblk_hash);
  
          /* initialise bioops hack */
          bioops.io_start = softdep_disk_io_initiation;
          bioops.io_complete = softdep_disk_write_complete;
          bioops.io_deallocate = softdep_deallocate_dependencies;
          bioops.io_countdeps = softdep_count_dependencies;
  }
  
  /*
   * Executed after all filesystems have been unmounted during
   * filesystem module unload.
   */
  void
  softdep_uninitialize()
  {
  
          hashdestroy(pagedep_hashtbl, M_PAGEDEP, pagedep_hash);
          hashdestroy(inodedep_hashtbl, M_INODEDEP, inodedep_hash);
          hashdestroy(newblk_hashtbl, M_NEWBLK, newblk_hash);
  }
  
  /*
   * Called at mount time to notify the dependency code that a
   * filesystem wishes to use it.
   */
  int
  softdep_mount(devvp, mp, fs, cred)
          struct vnode *devvp;
          struct mount *mp;
          struct fs *fs;
          struct ucred *cred;
  {
          struct csum_total cstotal;
          struct ufsmount *ump;
          struct cg *cgp;
          struct buf *bp;
          int error, cyl;
  
          MNT_ILOCK(mp);
          mp->mnt_flag = (mp->mnt_flag & ~MNT_ASYNC) | MNT_SOFTDEP;
          MNT_IUNLOCK(mp);
          ump = VFSTOUFS(mp);
          LIST_INIT(&ump->softdep_workitem_pending);
          ump->softdep_worklist_tail = NULL;
          ump->softdep_on_worklist = 0;
          ump->softdep_deps = 0;
          /*
           * When doing soft updates, the counters in the
           * superblock may have gotten out of sync. Recomputation
           * can take a long time and can be deferred for background
           * fsck.  However, the old behavior of scanning the cylinder
           * groups and recalculating them at mount time is available
           * by setting vfs.ffs.compute_summary_at_mount to one.
           */
          if (compute_summary_at_mount == 0 || fs->fs_clean != 0)
                  return (0);
          bzero(&cstotal, sizeof cstotal);
          for (cyl = 0; cyl < fs->fs_ncg; cyl++) {
                  if ((error = bread(devvp, fsbtodb(fs, cgtod(fs, cyl)),
                      fs->fs_cgsize, cred, &bp)) != 0) {
                          brelse(bp);
                          return (error);
                  }
                  cgp = (struct cg *)bp->b_data;
                  cstotal.cs_nffree += cgp->cg_cs.cs_nffree;
                  cstotal.cs_nbfree += cgp->cg_cs.cs_nbfree;
                  cstotal.cs_nifree += cgp->cg_cs.cs_nifree;
                  cstotal.cs_ndir += cgp->cg_cs.cs_ndir;
                  fs->fs_cs(fs, cyl) = cgp->cg_cs;
                  brelse(bp);
          }
  #ifdef DEBUG
          if (bcmp(&cstotal, &fs->fs_cstotal, sizeof cstotal))
                  printf("%s: superblock summary recomputed\n", fs->fs_fsmnt);
  #endif
          bcopy(&cstotal, &fs->fs_cstotal, sizeof cstotal);
          return (0);
  }
  
  /*
   * Protecting the freemaps (or bitmaps).
   * 
   * To eliminate the need to execute fsck before mounting a filesystem
   * after a power failure, one must (conservatively) guarantee that the
   * on-disk copy of the bitmaps never indicate that a live inode or block is
   * free.  So, when a block or inode is allocated, the bitmap should be
   * updated (on disk) before any new pointers.  When a block or inode is
   * freed, the bitmap should not be updated until all pointers have been
   * reset.  The latter dependency is handled by the delayed de-allocation
   * approach described below for block and inode de-allocation.  The former
   * dependency is handled by calling the following procedure when a block or
   * inode is allocated. When an inode is allocated an "inodedep" is created
   * with its DEPCOMPLETE flag cleared until its bitmap is written to disk.
   * Each "inodedep" is also inserted into the hash indexing structure so
   * that any additional link additions can be made dependent on the inode
   * allocation.
   * 
   * The ufs filesystem maintains a number of free block counts (e.g., per
   * cylinder group, per cylinder and per <cylinder, rotational position> pair)
   * in addition to the bitmaps.  These counts are used to improve efficiency
   * during allocation and therefore must be consistent with the bitmaps.
   * There is no convenient way to guarantee post-crash consistency of these
   * counts with simple update ordering, for two main reasons: (1) The counts
   * and bitmaps for a single cylinder group block are not in the same disk
   * sector.  If a disk write is interrupted (e.g., by power failure), one may
   * be written and the other not.  (2) Some of the counts are located in the
   * superblock rather than the cylinder group block. So, we focus our soft
   * updates implementation on protecting the bitmaps. When mounting a
   * filesystem, we recompute the auxiliary counts from the bitmaps.
   */
  
  /*
   * Called just after updating the cylinder group block to allocate an inode.
   */
  void
  softdep_setup_inomapdep(bp, ip, newinum)
          struct buf *bp;         /* buffer for cylgroup block with inode map */
          struct inode *ip;       /* inode related to allocation */
          ino_t newinum;          /* new inode number being allocated */
  {
          struct inodedep *inodedep;
          struct bmsafemap *bmsafemap;
  
          /*
           * Create a dependency for the newly allocated inode.
           * Panic if it already exists as something is seriously wrong.
           * Otherwise add it to the dependency list for the buffer holding
           * the cylinder group map from which it was allocated.
           */
          ACQUIRE_LOCK(&lk);
          if ((inodedep_lookup(UFSTOVFS(ip->i_ump), newinum, DEPALLOC|NODELAY,
              &inodedep)))
                  panic("softdep_setup_inomapdep: dependency for new inode "
                      "already exists");
          inodedep->id_buf = bp;
          inodedep->id_state &= ~DEPCOMPLETE;
          bmsafemap = bmsafemap_lookup(inodedep->id_list.wk_mp, bp);
          LIST_INSERT_HEAD(&bmsafemap->sm_inodedephd, inodedep, id_deps);
          FREE_LOCK(&lk);
  }
  
  /*
   * Called just after updating the cylinder group block to
   * allocate block or fragment.
   */
  void
  softdep_setup_blkmapdep(bp, mp, newblkno)
          struct buf *bp;         /* buffer for cylgroup block with block map */
          struct mount *mp;       /* filesystem doing allocation */
          ufs2_daddr_t newblkno;  /* number of newly allocated block */
  {
          struct newblk *newblk;
          struct bmsafemap *bmsafemap;
          struct fs *fs;
  
          fs = VFSTOUFS(mp)->um_fs;
          /*
           * Create a dependency for the newly allocated block.
           * Add it to the dependency list for the buffer holding
           * the cylinder group map from which it was allocated.
           */
          ACQUIRE_LOCK(&lk);
          if (newblk_lookup(fs, newblkno, DEPALLOC, &newblk) != 0)
                  panic("softdep_setup_blkmapdep: found block");
          newblk->nb_bmsafemap = bmsafemap = bmsafemap_lookup(mp, bp);
          LIST_INSERT_HEAD(&bmsafemap->sm_newblkhd, newblk, nb_deps);
          FREE_LOCK(&lk);
  }
  
  /*
   * Find the bmsafemap associated with a cylinder group buffer.
   * If none exists, create one. The buffer must be locked when
   * this routine is called and this routine must be called with
   * splbio interrupts blocked.
   */
  static struct bmsafemap *
  bmsafemap_lookup(mp, bp)
          struct mount *mp;
          struct buf *bp;
  {
          struct bmsafemap *bmsafemap;
          struct worklist *wk;
  
          mtx_assert(&lk, MA_OWNED);
          LIST_FOREACH(wk, &bp->b_dep, wk_list)
                  if (wk->wk_type == D_BMSAFEMAP)
                          return (WK_BMSAFEMAP(wk));
          FREE_LOCK(&lk);
          MALLOC(bmsafemap, struct bmsafemap *, sizeof(struct bmsafemap),
                  M_BMSAFEMAP, M_SOFTDEP_FLAGS);
          workitem_alloc(&bmsafemap->sm_list, D_BMSAFEMAP, mp);
          bmsafemap->sm_buf = bp;
          LIST_INIT(&bmsafemap->sm_allocdirecthd);
          LIST_INIT(&bmsafemap->sm_allocindirhd);
          LIST_INIT(&bmsafemap->sm_inodedephd);
          LIST_INIT(&bmsafemap->sm_newblkhd);
          ACQUIRE_LOCK(&lk);
          WORKLIST_INSERT(&bp->b_dep, &bmsafemap->sm_list);
          return (bmsafemap);
  }
  
  /*
   * Direct block allocation dependencies.
   * 
   * When a new block is allocated, the corresponding disk locations must be
   * initialized (with zeros or new data) before the on-disk inode points to
   * them.  Also, the freemap from which the block was allocated must be
   * updated (on disk) before the inode's pointer. These two dependencies are
   * independent of each other and are needed for all file blocks and indirect
   * blocks that are pointed to directly by the inode.  Just before the
   * "in-core" version of the inode is updated with a newly allocated block
   * number, a procedure (below) is called to setup allocation dependency
   * structures.  These structures are removed when the corresponding
   * dependencies are satisfied or when the block allocation becomes obsolete
   * (i.e., the file is deleted, the block is de-allocated, or the block is a
   * fragment that gets upgraded).  All of these cases are handled in
   * procedures described later.
   * 
   * When a file extension causes a fragment to be upgraded, either to a larger
   * fragment or to a full block, the on-disk location may change (if the
   * previous fragment could not simply be extended). In this case, the old
   * fragment must be de-allocated, but not until after the inode's pointer has
   * been updated. In most cases, this is handled by later procedures, which
   * will construct a "freefrag" structure to be added to the workitem queue
   * when the inode update is complete (or obsolete).  The main exception to
   * this is when an allocation occurs while a pending allocation dependency
   * (for the same block pointer) remains.  This case is handled in the main
   * allocation dependency setup procedure by immediately freeing the
   * unreferenced fragments.
   */ 
  void 
  softdep_setup_allocdirect(ip, lbn, newblkno, oldblkno, newsize, oldsize, bp)
          struct inode *ip;       /* inode to which block is being added */
          ufs_lbn_t lbn;          /* block pointer within inode */
          ufs2_daddr_t newblkno;  /* disk block number being added */
          ufs2_daddr_t oldblkno;  /* previous block number, 0 unless frag */
          long newsize;           /* size of new block */
          long oldsize;           /* size of new block */
          struct buf *bp;         /* bp for allocated block */
  {
          struct allocdirect *adp, *oldadp;
          struct allocdirectlst *adphead;
          struct bmsafemap *bmsafemap;
          struct inodedep *inodedep;
          struct pagedep *pagedep;
          struct newblk *newblk;
          struct mount *mp;
  
          mp = UFSTOVFS(ip->i_ump);
          MALLOC(adp, struct allocdirect *, sizeof(struct allocdirect),
                  M_ALLOCDIRECT, M_SOFTDEP_FLAGS|M_ZERO);
          workitem_alloc(&adp->ad_list, D_ALLOCDIRECT, mp);
          adp->ad_lbn = lbn;
          adp->ad_newblkno = newblkno;
          adp->ad_oldblkno = oldblkno;
          adp->ad_newsize = newsize;
          adp->ad_oldsize = oldsize;
          adp->ad_state = ATTACHED;
          LIST_INIT(&adp->ad_newdirblk);
          if (newblkno == oldblkno)
                  adp->ad_freefrag = NULL;
          else
                  adp->ad_freefrag = newfreefrag(ip, oldblkno, oldsize);
  
          ACQUIRE_LOCK(&lk);
          if (lbn >= NDADDR) {
                  /* allocating an indirect block */
                  if (oldblkno != 0)
                          panic("softdep_setup_allocdirect: non-zero indir");
          } else {
                  /*
                   * Allocating a direct block.
                   *
                   * If we are allocating a directory block, then we must
                   * allocate an associated pagedep to track additions and
                   * deletions.
                   */
                  if ((ip->i_mode & IFMT) == IFDIR &&
                      pagedep_lookup(ip, lbn, DEPALLOC, &pagedep) == 0)
                          WORKLIST_INSERT(&bp->b_dep, &pagedep->pd_list);
          }
          if (newblk_lookup(ip->i_fs, newblkno, 0, &newblk) == 0)
                  panic("softdep_setup_allocdirect: lost block");
          if (newblk->nb_state == DEPCOMPLETE) {
                  adp->ad_state |= DEPCOMPLETE;
                  adp->ad_buf = NULL;
          } else {
                  bmsafemap = newblk->nb_bmsafemap;
                  adp->ad_buf = bmsafemap->sm_buf;
                  LIST_REMOVE(newblk, nb_deps);
                  LIST_INSERT_HEAD(&bmsafemap->sm_allocdirecthd, adp, ad_deps);
          }
          LIST_REMOVE(newblk, nb_hash);
          FREE(newblk, M_NEWBLK);
  
          inodedep_lookup(mp, ip->i_number, DEPALLOC | NODELAY, &inodedep);
          adp->ad_inodedep = inodedep;
          WORKLIST_INSERT(&bp->b_dep, &adp->ad_list);
          /*
           * The list of allocdirects must be kept in sorted and ascending
           * order so that the rollback routines can quickly determine the
           * first uncommitted block (the size of the file stored on disk
           * ends at the end of the lowest committed fragment, or if there
           * are no fragments, at the end of the highest committed block).
           * Since files generally grow, the typical case is that the new
           * block is to be added at the end of the list. We speed this
           * special case by checking against the last allocdirect in the
           * list before laboriously traversing the list looking for the
           * insertion point.
           */
          adphead = &inodedep->id_newinoupdt;
          oldadp = TAILQ_LAST(adphead, allocdirectlst);
          if (oldadp == NULL || oldadp->ad_lbn <= lbn) {
                  /* insert at end of list */
                  TAILQ_INSERT_TAIL(adphead, adp, ad_next);
                  if (oldadp != NULL && oldadp->ad_lbn == lbn)
                          allocdirect_merge(adphead, adp, oldadp);
                  FREE_LOCK(&lk);
                  return;
          }
          TAILQ_FOREACH(oldadp, adphead, ad_next) {
                  if (oldadp->ad_lbn >= lbn)
                          break;
          }
          if (oldadp == NULL)
                  panic("softdep_setup_allocdirect: lost entry");
          /* insert in middle of list */
          TAILQ_INSERT_BEFORE(oldadp, adp, ad_next);
          if (oldadp->ad_lbn == lbn)
                  allocdirect_merge(adphead, adp, oldadp);
          FREE_LOCK(&lk);
  }
  
  /*
   * Replace an old allocdirect dependency with a newer one.
   * This routine must be called with splbio interrupts blocked.
   */
  static void
  allocdirect_merge(adphead, newadp, oldadp)
          struct allocdirectlst *adphead; /* head of list holding allocdirects */
          struct allocdirect *newadp;     /* allocdirect being added */
          struct allocdirect *oldadp;     /* existing allocdirect being checked */
  {
          struct worklist *wk;
          struct freefrag *freefrag;
          struct newdirblk *newdirblk;
  
          mtx_assert(&lk, MA_OWNED);
          if (newadp->ad_oldblkno != oldadp->ad_newblkno ||
              newadp->ad_oldsize != oldadp->ad_newsize ||
              newadp->ad_lbn >= NDADDR)
                  panic("%s %jd != new %jd || old size %ld != new %ld",
                      "allocdirect_merge: old blkno",
                      (intmax_t)newadp->ad_oldblkno,
                      (intmax_t)oldadp->ad_newblkno,
                      newadp->ad_oldsize, oldadp->ad_newsize);
          newadp->ad_oldblkno = oldadp->ad_oldblkno;
          newadp->ad_oldsize = oldadp->ad_oldsize;
          /*
           * If the old dependency had a fragment to free or had never
           * previously had a block allocated, then the new dependency
           * can immediately post its freefrag and adopt the old freefrag.
           * This action is done by swapping the freefrag dependencies.
           * The new dependency gains the old one's freefrag, and the
           * old one gets the new one and then immediately puts it on
           * the worklist when it is freed by free_allocdirect. It is
           * not possible to do this swap when the old dependency had a
           * non-zero size but no previous fragment to free. This condition
           * arises when the new block is an extension of the old block.
           * Here, the first part of the fragment allocated to the new
           * dependency is part of the block currently claimed on disk by
           * the old dependency, so cannot legitimately be freed until the
           * conditions for the new dependency are fulfilled.
           */
          if (oldadp->ad_freefrag != NULL || oldadp->ad_oldblkno == 0) {
                  freefrag = newadp->ad_freefrag;
                  newadp->ad_freefrag = oldadp->ad_freefrag;
                  oldadp->ad_freefrag = freefrag;
          }
          /*
           * If we are tracking a new directory-block allocation,
           * move it from the old allocdirect to the new allocdirect.
           */
          if ((wk = LIST_FIRST(&oldadp->ad_newdirblk)) != NULL) {
                  newdirblk = WK_NEWDIRBLK(wk);
                  WORKLIST_REMOVE(&newdirblk->db_list);
                  if (!LIST_EMPTY(&oldadp->ad_newdirblk))
                          panic("allocdirect_merge: extra newdirblk");
                  WORKLIST_INSERT(&newadp->ad_newdirblk, &newdirblk->db_list);
          }
          free_allocdirect(adphead, oldadp, 0);
  }
                  
  /*
   * Allocate a new freefrag structure if needed.
   */
  static struct freefrag *
  newfreefrag(ip, blkno, size)
          struct inode *ip;
          ufs2_daddr_t blkno;
          long size;
  {
          struct freefrag *freefrag;
          struct fs *fs;
  
          if (blkno == 0)
                  return (NULL);
          fs = ip->i_fs;
          if (fragnum(fs, blkno) + numfrags(fs, size) > fs->fs_frag)
                  panic("newfreefrag: frag size");
          MALLOC(freefrag, struct freefrag *, sizeof(struct freefrag),
                  M_FREEFRAG, M_SOFTDEP_FLAGS);
          workitem_alloc(&freefrag->ff_list, D_FREEFRAG, UFSTOVFS(ip->i_ump));
          freefrag->ff_inum = ip->i_number;
          freefrag->ff_blkno = blkno;
          freefrag->ff_fragsize = size;
          return (freefrag);
  }
  
  /*
   * This workitem de-allocates fragments that were replaced during
   * file block allocation.
   */
  static void 
  handle_workitem_freefrag(freefrag)
          struct freefrag *freefrag;
  {
          struct ufsmount *ump = VFSTOUFS(freefrag->ff_list.wk_mp);
  
          ffs_blkfree(ump, ump->um_fs, ump->um_devvp, freefrag->ff_blkno,
              freefrag->ff_fragsize, freefrag->ff_inum);
          ACQUIRE_LOCK(&lk);
          WORKITEM_FREE(freefrag, D_FREEFRAG);
          FREE_LOCK(&lk);
  }
  
  /*
   * Set up a dependency structure for an external attributes data block.
   * This routine follows much of the structure of softdep_setup_allocdirect.
   * See the description of softdep_setup_allocdirect above for details.
   */
  void 
  softdep_setup_allocext(ip, lbn, newblkno, oldblkno, newsize, oldsize, bp)
          struct inode *ip;
          ufs_lbn_t lbn;
          ufs2_daddr_t newblkno;
          ufs2_daddr_t oldblkno;
          long newsize;
          long oldsize;
          struct buf *bp;
  {
          struct allocdirect *adp, *oldadp;
          struct allocdirectlst *adphead;
          struct bmsafemap *bmsafemap;
          struct inodedep *inodedep;
          struct newblk *newblk;
          struct mount *mp;
  
          mp = UFSTOVFS(ip->i_ump);
          MALLOC(adp, struct allocdirect *, sizeof(struct allocdirect),
                  M_ALLOCDIRECT, M_SOFTDEP_FLAGS|M_ZERO);
          workitem_alloc(&adp->ad_list, D_ALLOCDIRECT, mp);
          adp->ad_lbn = lbn;
          adp->ad_newblkno = newblkno;
          adp->ad_oldblkno = oldblkno;
          adp->ad_newsize = newsize;
          adp->ad_oldsize = oldsize;
          adp->ad_state = ATTACHED | EXTDATA;
          LIST_INIT(&adp->ad_newdirblk);
          if (newblkno == oldblkno)
                  adp->ad_freefrag = NULL;
          else
                  adp->ad_freefrag = newfreefrag(ip, oldblkno, oldsize);
  
          ACQUIRE_LOCK(&lk);
          if (newblk_lookup(ip->i_fs, newblkno, 0, &newblk) == 0)
                  panic("softdep_setup_allocext: lost block");
  
          inodedep_lookup(mp, ip->i_number, DEPALLOC | NODELAY, &inodedep);
          adp->ad_inodedep = inodedep;
  
          if (newblk->nb_state == DEPCOMPLETE) {
                  adp->ad_state |= DEPCOMPLETE;
                  adp->ad_buf = NULL;
          } else {
                  bmsafemap = newblk->nb_bmsafemap;
                  adp->ad_buf = bmsafemap->sm_buf;
                  LIST_REMOVE(newblk, nb_deps);
                  LIST_INSERT_HEAD(&bmsafemap->sm_allocdirecthd, adp, ad_deps);
          }
          LIST_REMOVE(newblk, nb_hash);
          FREE(newblk, M_NEWBLK);
  
          WORKLIST_INSERT(&bp->b_dep, &adp->ad_list);
          if (lbn >= NXADDR)
                  panic("softdep_setup_allocext: lbn %lld > NXADDR",
                      (long long)lbn);
          /*
           * The list of allocdirects must be kept in sorted and ascending
           * order so that the rollback routines can quickly determine the
           * first uncommitted block (the size of the file stored on disk
           * ends at the end of the lowest committed fragment, or if there
           * are no fragments, at the end of the highest committed block).
           * Since files generally grow, the typical case is that the new
           * block is to be added at the end of the list. We speed this
           * special case by checking against the last allocdirect in the
           * list before laboriously traversing the list looking for the
           * insertion point.
           */
          adphead = &inodedep->id_newextupdt;
          oldadp = TAILQ_LAST(adphead, allocdirectlst);
          if (oldadp == NULL || oldadp->ad_lbn <= lbn) {
                  /* insert at end of list */
                  TAILQ_INSERT_TAIL(adphead, adp, ad_next);
                  if (oldadp != NULL && oldadp->ad_lbn == lbn)
                          allocdirect_merge(adphead, adp, oldadp);
                  FREE_LOCK(&lk);
                  return;
          }
          TAILQ_FOREACH(oldadp, adphead, ad_next) {
                  if (oldadp->ad_lbn >= lbn)
                          break;
          }
          if (oldadp == NULL)
                  panic("softdep_setup_allocext: lost entry");
          /* insert in middle of list */
          TAILQ_INSERT_BEFORE(oldadp, adp, ad_next);
          if (oldadp->ad_lbn == lbn)
                  allocdirect_merge(adphead, adp, oldadp);
          FREE_LOCK(&lk);
  }
  
  /*
   * Indirect block allocation dependencies.
   * 
   * The same dependencies that exist for a direct block also exist when
   * a new block is allocated and pointed to by an entry in a block of
   * indirect pointers. The undo/redo states described above are also
   * used here. Because an indirect block contains many pointers that
   * may have dependencies, a second copy of the entire in-memory indirect
   * block is kept. The buffer cache copy is always completely up-to-date.
   * The second copy, which is used only as a source for disk writes,
   * contains only the safe pointers (i.e., those that have no remaining
   * update dependencies). The second copy is freed when all pointers
   * are safe. The cache is not allowed to replace indirect blocks with
   * pending update dependencies. If a buffer containing an indirect
   * block with dependencies is written, these routines will mark it
   * dirty again. It can only be successfully written once all the
   * dependencies are removed. The ffs_fsync routine in conjunction with
   * softdep_sync_metadata work together to get all the dependencies
   * removed so that a file can be successfully written to disk. Three
   * procedures are used when setting up indirect block pointer
   * dependencies. The division is necessary because of the organization
   * of the "balloc" routine and because of the distinction between file
   * pages and file metadata blocks.
   */
  
  /*
   * Allocate a new allocindir structure.
   */
  static struct allocindir *
  newallocindir(ip, ptrno, newblkno, oldblkno)
          struct inode *ip;       /* inode for file being extended */
          int ptrno;              /* offset of pointer in indirect block */
          ufs2_daddr_t newblkno;  /* disk block number being added */
          ufs2_daddr_t oldblkno;  /* previous block number, 0 if none */
  {
          struct allocindir *aip;
  
          MALLOC(aip, struct allocindir *, sizeof(struct allocindir),
                  M_ALLOCINDIR, M_SOFTDEP_FLAGS|M_ZERO);
          workitem_alloc(&aip->ai_list, D_ALLOCINDIR, UFSTOVFS(ip->i_ump));
          aip->ai_state = ATTACHED;
          aip->ai_offset = ptrno;
          aip->ai_newblkno = newblkno;
          aip->ai_oldblkno = oldblkno;
          aip->ai_freefrag = newfreefrag(ip, oldblkno, ip->i_fs->fs_bsize);
          return (aip);
  }
  
  /*
   * Called just before setting an indirect block pointer
   * to a newly allocated file page.
   */
  void
  softdep_setup_allocindir_page(ip, lbn, bp, ptrno, newblkno, oldblkno, nbp)
          struct inode *ip;       /* inode for file being extended */
          ufs_lbn_t lbn;          /* allocated block number within file */
          struct buf *bp;         /* buffer with indirect blk referencing page */
          int ptrno;              /* offset of pointer in indirect block */
          ufs2_daddr_t newblkno;  /* disk block number being added */
          ufs2_daddr_t oldblkno;  /* previous block number, 0 if none */
          struct buf *nbp;        /* buffer holding allocated page */
  {
          struct allocindir *aip;
          struct pagedep *pagedep;
  
          ASSERT_VOP_LOCKED(ITOV(ip), "softdep_setup_allocindir_page");
          aip = newallocindir(ip, ptrno, newblkno, oldblkno);
          ACQUIRE_LOCK(&lk);
          /*
           * If we are allocating a directory page, then we must
           * allocate an associated pagedep to track additions and
           * deletions.
           */
          if ((ip->i_mode & IFMT) == IFDIR &&
              pagedep_lookup(ip, lbn, DEPALLOC, &pagedep) == 0)
                  WORKLIST_INSERT(&nbp->b_dep, &pagedep->pd_list);
          WORKLIST_INSERT(&nbp->b_dep, &aip->ai_list);
          setup_allocindir_phase2(bp, ip, aip);
          FREE_LOCK(&lk);
  }
  
  /*
   * Called just before setting an indirect block pointer to a
   * newly allocated indirect block.
   */
  void
  softdep_setup_allocindir_meta(nbp, ip, bp, ptrno, newblkno)
          struct buf *nbp;        /* newly allocated indirect block */
          struct inode *ip;       /* inode for file being extended */
          struct buf *bp;         /* indirect block referencing allocated block */
          int ptrno;              /* offset of pointer in indirect block */
          ufs2_daddr_t newblkno;  /* disk block number being added */
  {
          struct allocindir *aip;
  
          ASSERT_VOP_LOCKED(ITOV(ip), "softdep_setup_allocindir_meta");
          aip = newallocindir(ip, ptrno, newblkno, 0);
          ACQUIRE_LOCK(&lk);
          WORKLIST_INSERT(&nbp->b_dep, &aip->ai_list);
          setup_allocindir_phase2(bp, ip, aip);
          FREE_LOCK(&lk);
  }
  
  /*
   * Called to finish the allocation of the "aip" allocated
   * by one of the two routines above.
   */
  static void 
  setup_allocindir_phase2(bp, ip, aip)
          struct buf *bp;         /* in-memory copy of the indirect block */
          struct inode *ip;       /* inode for file being extended */
          struct allocindir *aip; /* allocindir allocated by the above routines */
  {
          struct worklist *wk;
          struct indirdep *indirdep, *newindirdep;
          struct bmsafemap *bmsafemap;
          struct allocindir *oldaip;
          struct freefrag *freefrag;
          struct newblk *newblk;
          ufs2_daddr_t blkno;
  
          mtx_assert(&lk, MA_OWNED);
          if (bp->b_lblkno >= 0)
                  panic("setup_allocindir_phase2: not indir blk");
          for (indirdep = NULL, newindirdep = NULL; ; ) {
                  LIST_FOREACH(wk, &bp->b_dep, wk_list) {
                          if (wk->wk_type != D_INDIRDEP)
                                  continue;
                          indirdep = WK_INDIRDEP(wk);
                          break;
                  }
                  if (indirdep == NULL && newindirdep) {
                          indirdep = newindirdep;
                          WORKLIST_INSERT(&bp->b_dep, &indirdep->ir_list);
                          newindirdep = NULL;
                  }
                  if (indirdep) {
                          if (newblk_lookup(ip->i_fs, aip->ai_newblkno, 0,
                              &newblk) == 0)
                                  panic("setup_allocindir: lost block");
                          if (newblk->nb_state == DEPCOMPLETE) {
                                  aip->ai_state |= DEPCOMPLETE;
                                  aip->ai_buf = NULL;
                          } else {
                                  bmsafemap = newblk->nb_bmsafemap;
                                  aip->ai_buf = bmsafemap->sm_buf;
                                  LIST_REMOVE(newblk, nb_deps);
                                  LIST_INSERT_HEAD(&bmsafemap->sm_allocindirhd,
                                      aip, ai_deps);
                          }
                          LIST_REMOVE(newblk, nb_hash);
                          FREE(newblk, M_NEWBLK);
                          aip->ai_indirdep = indirdep;
                          /*
                           * Check to see if there is an existing dependency
                           * for this block. If there is, merge the old
                           * dependency into the new one.
                           */
                          if (aip->ai_oldblkno == 0)
                                  oldaip = NULL;
                          else
  
                                  LIST_FOREACH(oldaip, &indirdep->ir_deplisthd, ai_next)
                                          if (oldaip->ai_offset == aip->ai_offset)
                                                  break;
                          freefrag = NULL;
                          if (oldaip != NULL) {
                                  if (oldaip->ai_newblkno != aip->ai_oldblkno)
                                          panic("setup_allocindir_phase2: blkno");
                                  aip->ai_oldblkno = oldaip->ai_oldblkno;
                                  freefrag = aip->ai_freefrag;
                                  aip->ai_freefrag = oldaip->ai_freefrag;
                                  oldaip->ai_freefrag = NULL;
                                  free_allocindir(oldaip, NULL);
                          }
                          LIST_INSERT_HEAD(&indirdep->ir_deplisthd, aip, ai_next);
                          if (ip->i_ump->um_fstype == UFS1)
                                  ((ufs1_daddr_t *)indirdep->ir_savebp->b_data)
                                      [aip->ai_offset] = aip->ai_oldblkno;
                          else
                                  ((ufs2_daddr_t *)indirdep->ir_savebp->b_data)
                                      [aip->ai_offset] = aip->ai_oldblkno;
                          FREE_LOCK(&lk);
                          if (freefrag != NULL)
                                  handle_workitem_freefrag(freefrag);
                  } else
                          FREE_LOCK(&lk);
                  if (newindirdep) {
                          newindirdep->ir_savebp->b_flags |= B_INVAL | B_NOCACHE;
                          brelse(newindirdep->ir_savebp);
                          ACQUIRE_LOCK(&lk);
                          WORKITEM_FREE((caddr_t)newindirdep, D_INDIRDEP);
                          if (indirdep)
                                  break;
                          FREE_LOCK(&lk);
                  }
                  if (indirdep) {
                          ACQUIRE_LOCK(&lk);
                          break;
                  }
                  MALLOC(newindirdep, struct indirdep *, sizeof(struct indirdep),
                          M_INDIRDEP, M_SOFTDEP_FLAGS);
                  workitem_alloc(&newindirdep->ir_list, D_INDIRDEP,
                      UFSTOVFS(ip->i_ump));
                  newindirdep->ir_state = ATTACHED;
                  if (ip->i_ump->um_fstype == UFS1)
                          newindirdep->ir_state |= UFS1FMT;
                  LIST_INIT(&newindirdep->ir_deplisthd);
                  LIST_INIT(&newindirdep->ir_donehd);
                  if (bp->b_blkno == bp->b_lblkno) {
                          ufs_bmaparray(bp->b_vp, bp->b_lblkno, &blkno, bp,
                              NULL, NULL);
                          bp->b_blkno = blkno;
                  }
                  newindirdep->ir_savebp =
                      getblk(ip->i_devvp, bp->b_blkno, bp->b_bcount, 0, 0, 0);
                  BUF_KERNPROC(newindirdep->ir_savebp);
                  bcopy(bp->b_data, newindirdep->ir_savebp->b_data, bp->b_bcount);
                  ACQUIRE_LOCK(&lk);
          }
  }
  
  /*
   * Block de-allocation dependencies.
   * 
   * When blocks are de-allocated, the on-disk pointers must be nullified before
   * the blocks are made available for use by other files.  (The true
   * requirement is that old pointers must be nullified before new on-disk
   * pointers are set.  We chose this slightly more stringent requirement to
   * reduce complexity.) Our implementation handles this dependency by updating
   * the inode (or indirect block) appropriately but delaying the actual block
   * de-allocation (i.e., freemap and free space count manipulation) until
   * after the updated versions reach stable storage.  After the disk is
   * updated, the blocks can be safely de-allocated whenever it is convenient.
   * This implementation handles only the common case of reducing a file's
   * length to zero. Other cases are handled by the conventional synchronous
   * write approach.
   *
   * The ffs implementation with which we worked double-checks
   * the state of the block pointers and file size as it reduces
   * a file's length.  Some of this code is replicated here in our
   * soft updates implementation.  The freeblks->fb_chkcnt field is
   * used to transfer a part of this information to the procedure
   * that eventually de-allocates the blocks.
   *
   * This routine should be called from the routine that shortens
   * a file's length, before the inode's size or block pointers
   * are modified. It will save the block pointer information for
   * later release and zero the inode so that the calling routine
   * can release it.
   */
  void
  softdep_setup_freeblocks(ip, length, flags)
          struct inode *ip;       /* The inode whose length is to be reduced */
          off_t length;           /* The new length for the file */
          int flags;              /* IO_EXT and/or IO_NORMAL */
  {
          struct freeblks *freeblks;
          struct inodedep *inodedep;
          struct allocdirect *adp;
          struct vnode *vp;
          struct buf *bp;
          struct fs *fs;
          ufs2_daddr_t extblocks, datablocks;
          struct mount *mp;
          int i, delay, error;
  
          fs = ip->i_fs;
          mp = UFSTOVFS(ip->i_ump);
          if (length != 0)
                  panic("softdep_setup_freeblocks: non-zero length");
          MALLOC(freeblks, struct freeblks *, sizeof(struct freeblks),
                  M_FREEBLKS, M_SOFTDEP_FLAGS|M_ZERO);
          workitem_alloc(&freeblks->fb_list, D_FREEBLKS, mp);
          freeblks->fb_state = ATTACHED;
          freeblks->fb_uid = ip->i_uid;
          freeblks->fb_previousinum = ip->i_number;
          freeblks->fb_devvp = ip->i_devvp;
          ACQUIRE_LOCK(&lk);
          num_freeblkdep++;
          FREE_LOCK(&lk);
          extblocks = 0;
          if (fs->fs_magic == FS_UFS2_MAGIC)
                  extblocks = btodb(fragroundup(fs, ip->i_din2->di_extsize));
          datablocks = DIP(ip, i_blocks) - extblocks;
          if ((flags & IO_NORMAL) == 0) {
                  freeblks->fb_oldsize = 0;
                  freeblks->fb_chkcnt = 0;
          } else {
                  freeblks->fb_oldsize = ip->i_size;
                  ip->i_size = 0;
                  DIP_SET(ip, i_size, 0);
                  freeblks->fb_chkcnt = datablocks;
                  for (i = 0; i < NDADDR; i++) {
                          freeblks->fb_dblks[i] = DIP(ip, i_db[i]);
                          DIP_SET(ip, i_db[i], 0);
                  }
                  for (i = 0; i < NIADDR; i++) {
                          freeblks->fb_iblks[i] = DIP(ip, i_ib[i]);
                          DIP_SET(ip, i_ib[i], 0);
                  }
                  /*
                   * If the file was removed, then the space being freed was
                   * accounted for then (see softdep_releasefile()). If the
                   * file is merely being truncated, then we account for it now.
                   */
                  if ((ip->i_flag & IN_SPACECOUNTED) == 0) {
                          UFS_LOCK(ip->i_ump);
                          fs->fs_pendingblocks += datablocks;
                          UFS_UNLOCK(ip->i_ump);
                  }
          }
          if ((flags & IO_EXT) == 0) {
                  freeblks->fb_oldextsize = 0;
          } else {
                  freeblks->fb_oldextsize = ip->i_din2->di_extsize;
                  ip->i_din2->di_extsize = 0;
                  freeblks->fb_chkcnt += extblocks;
                  for (i = 0; i < NXADDR; i++) {
                          freeblks->fb_eblks[i] = ip->i_din2->di_extb[i];
                          ip->i_din2->di_extb[i] = 0;
                  }
          }
          DIP_SET(ip, i_blocks, DIP(ip, i_blocks) - freeblks->fb_chkcnt);
          /*
           * Push the zero'ed inode to to its disk buffer so that we are free
           * to delete its dependencies below. Once the dependencies are gone
           * the buffer can be safely released.
           */
          if ((error = bread(ip->i_devvp,
              fsbtodb(fs, ino_to_fsba(fs, ip->i_number)),
              (int)fs->fs_bsize, NOCRED, &bp)) != 0) {
                  brelse(bp);
                  softdep_error("softdep_setup_freeblocks", error);
          }
          if (ip->i_ump->um_fstype == UFS1)
                  *((struct ufs1_dinode *)bp->b_data +
                      ino_to_fsbo(fs, ip->i_number)) = *ip->i_din1;
          else
                  *((struct ufs2_dinode *)bp->b_data +
                      ino_to_fsbo(fs, ip->i_number)) = *ip->i_din2;
          /*
           * Find and eliminate any inode dependencies.
           */
          ACQUIRE_LOCK(&lk);
          (void) inodedep_lookup(mp, ip->i_number, DEPALLOC, &inodedep);
          if ((inodedep->id_state & IOSTARTED) != 0)
                  panic("softdep_setup_freeblocks: inode busy");
          /*
           * Add the freeblks structure to the list of operations that
           * must await the zero'ed inode being written to disk. If we
           * still have a bitmap dependency (delay == 0), then the inode
           * has never been written to disk, so we can process the
           * freeblks below once we have deleted the dependencies.
           */
          delay = (inodedep->id_state & DEPCOMPLETE);
          if (delay)
                  WORKLIST_INSERT(&inodedep->id_bufwait, &freeblks->fb_list);
          /*
           * Because the file length has been truncated to zero, any
           * pending block allocation dependency structures associated
           * with this inode are obsolete and can simply be de-allocated.
           * We must first merge the two dependency lists to get rid of
           * any duplicate freefrag structures, then purge the merged list.
           * If we still have a bitmap dependency, then the inode has never
           * been written to disk, so we can free any fragments without delay.
           */
          if (flags & IO_NORMAL) {
                  merge_inode_lists(&inodedep->id_newinoupdt,
                      &inodedep->id_inoupdt);
                  while ((adp = TAILQ_FIRST(&inodedep->id_inoupdt)) != 0)
                          free_allocdirect(&inodedep->id_inoupdt, adp, delay);
          }
          if (flags & IO_EXT) {
                  merge_inode_lists(&inodedep->id_newextupdt,
                      &inodedep->id_extupdt);
                  while ((adp = TAILQ_FIRST(&inodedep->id_extupdt)) != 0)
                          free_allocdirect(&inodedep->id_extupdt, adp, delay);
          }
          FREE_LOCK(&lk);
          bdwrite(bp);
          /*
           * We must wait for any I/O in progress to finish so that
           * all potential buffers on the dirty list will be visible.
           * Once they are all there, walk the list and get rid of
           * any dependencies.
           */
          vp = ITOV(ip);
          VI_LOCK(vp);
          drain_output(vp);
  restart:
          TAILQ_FOREACH(bp, &vp->v_bufobj.bo_dirty.bv_hd, b_bobufs) {
                  if (((flags & IO_EXT) == 0 && (bp->b_xflags & BX_ALTDATA)) ||
                      ((flags & IO_NORMAL) == 0 &&
                        (bp->b_xflags & BX_ALTDATA) == 0))
                          continue;
                  if ((bp = getdirtybuf(bp, VI_MTX(vp), MNT_WAIT)) == NULL)
                          goto restart;
                  VI_UNLOCK(vp);
                  ACQUIRE_LOCK(&lk);
                  (void) inodedep_lookup(mp, ip->i_number, 0, &inodedep);
                  deallocate_dependencies(bp, inodedep);
                  FREE_LOCK(&lk);
                  bp->b_flags |= B_INVAL | B_NOCACHE;
                  brelse(bp);
                  VI_LOCK(vp);
                  goto restart;
          }
          VI_UNLOCK(vp);
          ACQUIRE_LOCK(&lk);
          if (inodedep_lookup(mp, ip->i_number, 0, &inodedep) != 0)
                  (void) free_inodedep(inodedep);
  
          if(delay) {
                  freeblks->fb_state |= DEPCOMPLETE;
                  /*
                   * If the inode with zeroed block pointers is now on disk
                   * we can start freeing blocks. Add freeblks to the worklist
                   * instead of calling  handle_workitem_freeblocks directly as
                   * it is more likely that additional IO is needed to complete
                   * the request here than in the !delay case.
                   */  
                  if ((freeblks->fb_state & ALLCOMPLETE) == ALLCOMPLETE)
                          add_to_worklist(&freeblks->fb_list);
          }
  
          FREE_LOCK(&lk);
          /*
           * If the inode has never been written to disk (delay == 0),
           * then we can process the freeblks now that we have deleted
           * the dependencies.
           */
          if (!delay)
                  handle_workitem_freeblocks(freeblks, 0);
  }
  
  /*
   * Reclaim any dependency structures from a buffer that is about to
   * be reallocated to a new vnode. The buffer must be locked, thus,
   * no I/O completion operations can occur while we are manipulating
   * its associated dependencies. The mutex is held so that other I/O's
   * associated with related dependencies do not occur.
   */
  static void
  deallocate_dependencies(bp, inodedep)
          struct buf *bp;
          struct inodedep *inodedep;
  {
          struct worklist *wk;
          struct indirdep *indirdep;
          struct allocindir *aip;
          struct pagedep *pagedep;
          struct dirrem *dirrem;
          struct diradd *dap;
          int i;
  
          mtx_assert(&lk, MA_OWNED);
          while ((wk = LIST_FIRST(&bp->b_dep)) != NULL) {
                  switch (wk->wk_type) {
  
                  case D_INDIRDEP:
                          indirdep = WK_INDIRDEP(wk);
                          /*
                           * None of the indirect pointers will ever be visible,
                           * so they can simply be tossed. GOINGAWAY ensures
                           * that allocated pointers will be saved in the buffer
                           * cache until they are freed. Note that they will
                           * only be able to be found by their physical address
                           * since the inode mapping the logical address will
                           * be gone. The save buffer used for the safe copy
                           * was allocated in setup_allocindir_phase2 using
                           * the physical address so it could be used for this
                           * purpose. Hence we swap the safe copy with the real
                           * copy, allowing the safe copy to be freed and holding
                           * on to the real copy for later use in indir_trunc.
                           */
                          if (indirdep->ir_state & GOINGAWAY)
                                  panic("deallocate_dependencies: already gone");
                          indirdep->ir_state |= GOINGAWAY;
                          VFSTOUFS(bp->b_vp->v_mount)->um_numindirdeps += 1;
                          while ((aip = LIST_FIRST(&indirdep->ir_deplisthd)) != 0)
                                  free_allocindir(aip, inodedep);
                          if (bp->b_lblkno >= 0 ||
                              bp->b_blkno != indirdep->ir_savebp->b_lblkno)
                                  panic("deallocate_dependencies: not indir");
                          bcopy(bp->b_data, indirdep->ir_savebp->b_data,
                              bp->b_bcount);
                          WORKLIST_REMOVE(wk);
                          WORKLIST_INSERT(&indirdep->ir_savebp->b_dep, wk);
                          continue;
  
                  case D_PAGEDEP:
                          pagedep = WK_PAGEDEP(wk);
                          /*
                           * None of the directory additions will ever be
                           * visible, so they can simply be tossed.
                           */
                          for (i = 0; i < DAHASHSZ; i++)
                                  while ((dap =
                                      LIST_FIRST(&pagedep->pd_diraddhd[i])))
                                          free_diradd(dap);
                          while ((dap = LIST_FIRST(&pagedep->pd_pendinghd)) != 0)
                                  free_diradd(dap);
                          /*
                           * Copy any directory remove dependencies to the list
                           * to be processed after the zero'ed inode is written.
                           * If the inode has already been written, then they 
                           * can be dumped directly onto the work list.
                           */
                          LIST_FOREACH(dirrem, &pagedep->pd_dirremhd, dm_next) {
                                  LIST_REMOVE(dirrem, dm_next);
                                  dirrem->dm_dirinum = pagedep->pd_ino;
                                  if (inodedep == NULL ||
                                      (inodedep->id_state & ALLCOMPLETE) ==
                                       ALLCOMPLETE)
                                          add_to_worklist(&dirrem->dm_list);
                                  else
                                          WORKLIST_INSERT(&inodedep->id_bufwait,
                                              &dirrem->dm_list);
                          }
                          if ((pagedep->pd_state & NEWBLOCK) != 0) {
                                  LIST_FOREACH(wk, &inodedep->id_bufwait, wk_list)
                                          if (wk->wk_type == D_NEWDIRBLK &&
                                              WK_NEWDIRBLK(wk)->db_pagedep ==
                                                pagedep)
                                                  break;
                                  if (wk != NULL) {
                                          WORKLIST_REMOVE(wk);
                                          free_newdirblk(WK_NEWDIRBLK(wk));
                                  } else
                                          panic("deallocate_dependencies: "
                                                "lost pagedep");
                          }
                          WORKLIST_REMOVE(&pagedep->pd_list);
                          LIST_REMOVE(pagedep, pd_hash);
                          WORKITEM_FREE(pagedep, D_PAGEDEP);
                          continue;
  
                  case D_ALLOCINDIR:
                          free_allocindir(WK_ALLOCINDIR(wk), inodedep);
                          continue;
  
                  case D_ALLOCDIRECT:
                  case D_INODEDEP:
                          panic("deallocate_dependencies: Unexpected type %s",
                              TYPENAME(wk->wk_type));
                          /* NOTREACHED */
  
                  default:
                          panic("deallocate_dependencies: Unknown type %s",
                              TYPENAME(wk->wk_type));
                          /* NOTREACHED */
                  }
          }
  }
  
  /*
   * Free an allocdirect. Generate a new freefrag work request if appropriate.
   * This routine must be called with splbio interrupts blocked.
   */
  static void
  free_allocdirect(adphead, adp, delay)
          struct allocdirectlst *adphead;
          struct allocdirect *adp;
          int delay;
  {
          struct newdirblk *newdirblk;
          struct worklist *wk;
  
          mtx_assert(&lk, MA_OWNED);
          if ((adp->ad_state & DEPCOMPLETE) == 0)
                  LIST_REMOVE(adp, ad_deps);
          TAILQ_REMOVE(adphead, adp, ad_next);
          if ((adp->ad_state & COMPLETE) == 0)
                  WORKLIST_REMOVE(&adp->ad_list);
          if (adp->ad_freefrag != NULL) {
                  if (delay)
                          WORKLIST_INSERT(&adp->ad_inodedep->id_bufwait,
                              &adp->ad_freefrag->ff_list);
                  else
                          add_to_worklist(&adp->ad_freefrag->ff_list);
          }
          if ((wk = LIST_FIRST(&adp->ad_newdirblk)) != NULL) {
                  newdirblk = WK_NEWDIRBLK(wk);
                  WORKLIST_REMOVE(&newdirblk->db_list);
                  if (!LIST_EMPTY(&adp->ad_newdirblk))
                          panic("free_allocdirect: extra newdirblk");
                  if (delay)
                          WORKLIST_INSERT(&adp->ad_inodedep->id_bufwait,
                              &newdirblk->db_list);
                  else
                          free_newdirblk(newdirblk);
          }
          WORKITEM_FREE(adp, D_ALLOCDIRECT);
  }
  
  /*
   * Free a newdirblk. Clear the NEWBLOCK flag on its associated pagedep.
   * This routine must be called with splbio interrupts blocked.
   */
  static void
  free_newdirblk(newdirblk)
          struct newdirblk *newdirblk;
  {
          struct pagedep *pagedep;
          struct diradd *dap;
          int i;
  
          mtx_assert(&lk, MA_OWNED);
          /*
           * If the pagedep is still linked onto the directory buffer
           * dependency chain, then some of the entries on the
           * pd_pendinghd list may not be committed to disk yet. In
           * this case, we will simply clear the NEWBLOCK flag and
           * let the pd_pendinghd list be processed when the pagedep
           * is next written. If the pagedep is no longer on the buffer
           * dependency chain, then all the entries on the pd_pending
           * list are committed to disk and we can free them here.
           */
          pagedep = newdirblk->db_pagedep;
          pagedep->pd_state &= ~NEWBLOCK;
          if ((pagedep->pd_state & ONWORKLIST) == 0)
                  while ((dap = LIST_FIRST(&pagedep->pd_pendinghd)) != NULL)
                          free_diradd(dap);
          /*
           * If no dependencies remain, the pagedep will be freed.
           */
          for (i = 0; i < DAHASHSZ; i++)
                  if (!LIST_EMPTY(&pagedep->pd_diraddhd[i]))
                          break;
          if (i == DAHASHSZ && (pagedep->pd_state & ONWORKLIST) == 0) {
                  LIST_REMOVE(pagedep, pd_hash);
                  WORKITEM_FREE(pagedep, D_PAGEDEP);
          }
          WORKITEM_FREE(newdirblk, D_NEWDIRBLK);
  }
  
  /*
   * Prepare an inode to be freed. The actual free operation is not
   * done until the zero'ed inode has been written to disk.
   */
  void
  softdep_freefile(pvp, ino, mode)
          struct vnode *pvp;
          ino_t ino;
          int mode;
  {
          struct inode *ip = VTOI(pvp);
          struct inodedep *inodedep;
          struct freefile *freefile;
  
          /*
           * This sets up the inode de-allocation dependency.
           */
          MALLOC(freefile, struct freefile *, sizeof(struct freefile),
                  M_FREEFILE, M_SOFTDEP_FLAGS);
          workitem_alloc(&freefile->fx_list, D_FREEFILE, pvp->v_mount);
          freefile->fx_mode = mode;
          freefile->fx_oldinum = ino;
          freefile->fx_devvp = ip->i_devvp;
          if ((ip->i_flag & IN_SPACECOUNTED) == 0) {
                  UFS_LOCK(ip->i_ump);
                  ip->i_fs->fs_pendinginodes += 1;
                  UFS_UNLOCK(ip->i_ump);
          }
  
          /*
           * If the inodedep does not exist, then the zero'ed inode has
           * been written to disk. If the allocated inode has never been
           * written to disk, then the on-disk inode is zero'ed. In either
           * case we can free the file immediately.
           */
          ACQUIRE_LOCK(&lk);
          if (inodedep_lookup(pvp->v_mount, ino, 0, &inodedep) == 0 ||
              check_inode_unwritten(inodedep)) {
                  FREE_LOCK(&lk);
                  handle_workitem_freefile(freefile);
                  return;
          }
          WORKLIST_INSERT(&inodedep->id_inowait, &freefile->fx_list);
          FREE_LOCK(&lk);
          ip->i_flag |= IN_MODIFIED;
  }
  
  /*
   * Check to see if an inode has never been written to disk. If
   * so free the inodedep and return success, otherwise return failure.
   * This routine must be called with splbio interrupts blocked.
   *
   * If we still have a bitmap dependency, then the inode has never
   * been written to disk. Drop the dependency as it is no longer
   * necessary since the inode is being deallocated. We set the
   * ALLCOMPLETE flags since the bitmap now properly shows that the
   * inode is not allocated. Even if the inode is actively being
   * written, it has been rolled back to its zero'ed state, so we
   * are ensured that a zero inode is what is on the disk. For short
   * lived files, this change will usually result in removing all the
   * dependencies from the inode so that it can be freed immediately.
   */
  static int
  check_inode_unwritten(inodedep)
          struct inodedep *inodedep;
  {
  
          mtx_assert(&lk, MA_OWNED);
          if ((inodedep->id_state & DEPCOMPLETE) != 0 ||
              !LIST_EMPTY(&inodedep->id_pendinghd) ||
              !LIST_EMPTY(&inodedep->id_bufwait) ||
              !LIST_EMPTY(&inodedep->id_inowait) ||
              !TAILQ_EMPTY(&inodedep->id_inoupdt) ||
              !TAILQ_EMPTY(&inodedep->id_newinoupdt) ||
              !TAILQ_EMPTY(&inodedep->id_extupdt) ||
              !TAILQ_EMPTY(&inodedep->id_newextupdt) ||
              inodedep->id_nlinkdelta != 0)
                  return (0);
  
          /*
           * Another process might be in initiate_write_inodeblock_ufs[12]
           * trying to allocate memory without holding "Softdep Lock".
           */
          if ((inodedep->id_state & IOSTARTED) != 0 &&
              inodedep->id_savedino1 == NULL)
                  return (0);
  
          inodedep->id_state |= ALLCOMPLETE;
          LIST_REMOVE(inodedep, id_deps);
          inodedep->id_buf = NULL;
          if (inodedep->id_state & ONWORKLIST)
                  WORKLIST_REMOVE(&inodedep->id_list);
          if (inodedep->id_savedino1 != NULL) {
                  FREE(inodedep->id_savedino1, M_SAVEDINO);
                  inodedep->id_savedino1 = NULL;
          }
          if (free_inodedep(inodedep) == 0)
                  panic("check_inode_unwritten: busy inode");
          return (1);
  }
  
  /*
   * Try to free an inodedep structure. Return 1 if it could be freed.
   */
  static int
  free_inodedep(inodedep)
          struct inodedep *inodedep;
  {
  
          mtx_assert(&lk, MA_OWNED);
          if ((inodedep->id_state & ONWORKLIST) != 0 ||
              (inodedep->id_state & ALLCOMPLETE) != ALLCOMPLETE ||
              !LIST_EMPTY(&inodedep->id_pendinghd) ||
              !LIST_EMPTY(&inodedep->id_bufwait) ||
              !LIST_EMPTY(&inodedep->id_inowait) ||
              !TAILQ_EMPTY(&inodedep->id_inoupdt) ||
              !TAILQ_EMPTY(&inodedep->id_newinoupdt) ||
              !TAILQ_EMPTY(&inodedep->id_extupdt) ||
              !TAILQ_EMPTY(&inodedep->id_newextupdt) ||
              inodedep->id_nlinkdelta != 0 || inodedep->id_savedino1 != NULL)
                  return (0);
          LIST_REMOVE(inodedep, id_hash);
          WORKITEM_FREE(inodedep, D_INODEDEP);
          num_inodedep -= 1;
          return (1);
  }
  
  /*
   * This workitem routine performs the block de-allocation.
   * The workitem is added to the pending list after the updated
   * inode block has been written to disk.  As mentioned above,
   * checks regarding the number of blocks de-allocated (compared
   * to the number of blocks allocated for the file) are also
   * performed in this function.
   */
  static void
  handle_workitem_freeblocks(freeblks, flags)
          struct freeblks *freeblks;
          int flags;
  {
          struct inode *ip;
          struct vnode *vp;
          struct fs *fs;
          struct ufsmount *ump;
          int i, nblocks, level, bsize;
          ufs2_daddr_t bn, blocksreleased = 0;
          int error, allerror = 0;
          ufs_lbn_t baselbns[NIADDR], tmpval;
          int fs_pendingblocks;
  
          ump = VFSTOUFS(freeblks->fb_list.wk_mp);
          fs = ump->um_fs;
          fs_pendingblocks = 0;
          tmpval = 1;
          baselbns[0] = NDADDR;
          for (i = 1; i < NIADDR; i++) {
                  tmpval *= NINDIR(fs);
                  baselbns[i] = baselbns[i - 1] + tmpval;
          }
          nblocks = btodb(fs->fs_bsize);
          blocksreleased = 0;
          /*
           * Release all extended attribute blocks or frags.
           */
          if (freeblks->fb_oldextsize > 0) {
                  for (i = (NXADDR - 1); i >= 0; i--) {
                          if ((bn = freeblks->fb_eblks[i]) == 0)
                                  continue;
                          bsize = sblksize(fs, freeblks->fb_oldextsize, i);
                          ffs_blkfree(ump, fs, freeblks->fb_devvp, bn, bsize,
                              freeblks->fb_previousinum);
                          blocksreleased += btodb(bsize);
                  }
          }
          /*
           * Release all data blocks or frags.
           */
          if (freeblks->fb_oldsize > 0) {
                  /*
                   * Indirect blocks first.
                   */
                  for (level = (NIADDR - 1); level >= 0; level--) {
                          if ((bn = freeblks->fb_iblks[level]) == 0)
                                  continue;
                          if ((error = indir_trunc(freeblks, fsbtodb(fs, bn),
                              level, baselbns[level], &blocksreleased)) != 0)
                                  allerror = error;
                          ffs_blkfree(ump, fs, freeblks->fb_devvp, bn,
                              fs->fs_bsize, freeblks->fb_previousinum);
                          fs_pendingblocks += nblocks;
                          blocksreleased += nblocks;
                  }
                  /*
                   * All direct blocks or frags.
                   */
                  for (i = (NDADDR - 1); i >= 0; i--) {
                          if ((bn = freeblks->fb_dblks[i]) == 0)
                                  continue;
                          bsize = sblksize(fs, freeblks->fb_oldsize, i);
                          ffs_blkfree(ump, fs, freeblks->fb_devvp, bn, bsize,
                              freeblks->fb_previousinum);
                          fs_pendingblocks += btodb(bsize);
                          blocksreleased += btodb(bsize);
                  }
          }
          UFS_LOCK(ump);
          fs->fs_pendingblocks -= fs_pendingblocks;
          UFS_UNLOCK(ump);
          /*
           * If we still have not finished background cleanup, then check
           * to see if the block count needs to be adjusted.
           */
          if (freeblks->fb_chkcnt != blocksreleased &&
              (fs->fs_flags & FS_UNCLEAN) != 0 &&
              ffs_vget(freeblks->fb_list.wk_mp, freeblks->fb_previousinum,
              (flags & LK_NOWAIT) | LK_EXCLUSIVE, &vp) == 0) {
                  ip = VTOI(vp);
                  DIP_SET(ip, i_blocks, DIP(ip, i_blocks) + \
                      freeblks->fb_chkcnt - blocksreleased);
                  ip->i_flag |= IN_CHANGE;
                  vput(vp);
          }
  
  #ifdef INVARIANTS
          if (freeblks->fb_chkcnt != blocksreleased &&
              ((fs->fs_flags & FS_UNCLEAN) == 0 || (flags & LK_NOWAIT) != 0))
                  printf("handle_workitem_freeblocks: block count\n");
          if (allerror)
                  softdep_error("handle_workitem_freeblks", allerror);
  #endif /* INVARIANTS */
  
          ACQUIRE_LOCK(&lk);
          WORKITEM_FREE(freeblks, D_FREEBLKS);
          num_freeblkdep--;
          FREE_LOCK(&lk);
  }
  
  /*
   * Release blocks associated with the inode ip and stored in the indirect
   * block dbn. If level is greater than SINGLE, the block is an indirect block
   * and recursive calls to indirtrunc must be used to cleanse other indirect
   * blocks.
   */
  static int
  indir_trunc(freeblks, dbn, level, lbn, countp)
          struct freeblks *freeblks;
          ufs2_daddr_t dbn;
          int level;
          ufs_lbn_t lbn;
          ufs2_daddr_t *countp;
  {
          struct buf *bp;
          struct fs *fs;
          struct worklist *wk;
          struct indirdep *indirdep;
          struct ufsmount *ump;
          ufs1_daddr_t *bap1 = 0;
          ufs2_daddr_t nb, *bap2 = 0;
          ufs_lbn_t lbnadd;
          int i, nblocks, ufs1fmt;
          int error, allerror = 0;
          int fs_pendingblocks;
  
          ump = VFSTOUFS(freeblks->fb_list.wk_mp);
          fs = ump->um_fs;
          fs_pendingblocks = 0;
          lbnadd = 1;
          for (i = level; i > 0; i--)
                  lbnadd *= NINDIR(fs);
          /*
           * Get buffer of block pointers to be freed. This routine is not
           * called until the zero'ed inode has been written, so it is safe
           * to free blocks as they are encountered. Because the inode has
           * been zero'ed, calls to bmap on these blocks will fail. So, we
           * have to use the on-disk address and the block device for the
           * filesystem to look them up. If the file was deleted before its
           * indirect blocks were all written to disk, the routine that set
           * us up (deallocate_dependencies) will have arranged to leave
           * a complete copy of the indirect block in memory for our use.
           * Otherwise we have to read the blocks in from the disk.
           */
  #ifdef notyet
          bp = getblk(freeblks->fb_devvp, dbn, (int)fs->fs_bsize, 0, 0,
              GB_NOCREAT);
  #else
          bp = incore(&freeblks->fb_devvp->v_bufobj, dbn);
  #endif
          ACQUIRE_LOCK(&lk);
          if (bp != NULL && (wk = LIST_FIRST(&bp->b_dep)) != NULL) {
                  if (wk->wk_type != D_INDIRDEP ||
                      (indirdep = WK_INDIRDEP(wk))->ir_savebp != bp ||
                      (indirdep->ir_state & GOINGAWAY) == 0)
                          panic("indir_trunc: lost indirdep");
                  WORKLIST_REMOVE(wk);
                  WORKITEM_FREE(indirdep, D_INDIRDEP);
                  if (!LIST_EMPTY(&bp->b_dep))
                          panic("indir_trunc: dangling dep");
                  ump->um_numindirdeps -= 1;
                  FREE_LOCK(&lk);
          } else {
  #ifdef notyet
                  if (bp)
                          brelse(bp);
  #endif
                  FREE_LOCK(&lk);
                  error = bread(freeblks->fb_devvp, dbn, (int)fs->fs_bsize,
                      NOCRED, &bp);
                  if (error) {
                          brelse(bp);
                          return (error);
                  }
          }
          /*
           * Recursively free indirect blocks.
           */
          if (ump->um_fstype == UFS1) {
                  ufs1fmt = 1;
                  bap1 = (ufs1_daddr_t *)bp->b_data;
          } else {
                  ufs1fmt = 0;
                  bap2 = (ufs2_daddr_t *)bp->b_data;
          }
          nblocks = btodb(fs->fs_bsize);
          for (i = NINDIR(fs) - 1; i >= 0; i--) {
                  if (ufs1fmt)
                          nb = bap1[i];
                  else
                          nb = bap2[i];
                  if (nb == 0)
                          continue;
                  if (level != 0) {
                          if ((error = indir_trunc(freeblks, fsbtodb(fs, nb),
                               level - 1, lbn + (i * lbnadd), countp)) != 0)
                                  allerror = error;
                  }
                  ffs_blkfree(ump, fs, freeblks->fb_devvp, nb, fs->fs_bsize,
                      freeblks->fb_previousinum);
                  fs_pendingblocks += nblocks;
                  *countp += nblocks;
          }
          UFS_LOCK(ump);
          fs->fs_pendingblocks -= fs_pendingblocks;
          UFS_UNLOCK(ump);
          bp->b_flags |= B_INVAL | B_NOCACHE;
          brelse(bp);
          return (allerror);
  }
  
  /*
   * Free an allocindir.
   * This routine must be called with splbio interrupts blocked.
   */
  static void
  free_allocindir(aip, inodedep)
          struct allocindir *aip;
          struct inodedep *inodedep;
  {
          struct freefrag *freefrag;
  
          mtx_assert(&lk, MA_OWNED);
          if ((aip->ai_state & DEPCOMPLETE) == 0)
                  LIST_REMOVE(aip, ai_deps);
          if (aip->ai_state & ONWORKLIST)
                  WORKLIST_REMOVE(&aip->ai_list);
          LIST_REMOVE(aip, ai_next);
          if ((freefrag = aip->ai_freefrag) != NULL) {
                  if (inodedep == NULL)
                          add_to_worklist(&freefrag->ff_list);
                  else
                          WORKLIST_INSERT(&inodedep->id_bufwait,
                              &freefrag->ff_list);
          }
          WORKITEM_FREE(aip, D_ALLOCINDIR);
  }
  
  /*
   * Directory entry addition dependencies.
   * 
   * When adding a new directory entry, the inode (with its incremented link
   * count) must be written to disk before the directory entry's pointer to it.
   * Also, if the inode is newly allocated, the corresponding freemap must be
   * updated (on disk) before the directory entry's pointer. These requirements
   * are met via undo/redo on the directory entry's pointer, which consists
   * simply of the inode number.
   * 
   * As directory entries are added and deleted, the free space within a
   * directory block can become fragmented.  The ufs filesystem will compact
   * a fragmented directory block to make space for a new entry. When this
   * occurs, the offsets of previously added entries change. Any "diradd"
   * dependency structures corresponding to these entries must be updated with
   * the new offsets.
   */
  
  /*
   * This routine is called after the in-memory inode's link
   * count has been incremented, but before the directory entry's
   * pointer to the inode has been set.
   */
  int
  softdep_setup_directory_add(bp, dp, diroffset, newinum, newdirbp, isnewblk)
          struct buf *bp;         /* buffer containing directory block */
          struct inode *dp;       /* inode for directory */
          off_t diroffset;        /* offset of new entry in directory */
          ino_t newinum;          /* inode referenced by new directory entry */
          struct buf *newdirbp;   /* non-NULL => contents of new mkdir */
          int isnewblk;           /* entry is in a newly allocated block */
  {
          int offset;             /* offset of new entry within directory block */
          ufs_lbn_t lbn;          /* block in directory containing new entry */
          struct fs *fs;
          struct diradd *dap;
          struct allocdirect *adp;
          struct pagedep *pagedep;
          struct inodedep *inodedep;
          struct newdirblk *newdirblk = 0;
          struct mkdir *mkdir1, *mkdir2;
          struct mount *mp;
  
          /*
           * Whiteouts have no dependencies.
           */
          if (newinum == WINO) {
                  if (newdirbp != NULL)
                          bdwrite(newdirbp);
                  return (0);
          }
          mp = UFSTOVFS(dp->i_ump);
          fs = dp->i_fs;
          lbn = lblkno(fs, diroffset);
          offset = blkoff(fs, diroffset);
          MALLOC(dap, struct diradd *, sizeof(struct diradd), M_DIRADD,
                  M_SOFTDEP_FLAGS|M_ZERO);
          workitem_alloc(&dap->da_list, D_DIRADD, mp);
          dap->da_offset = offset;
          dap->da_newinum = newinum;
          dap->da_state = ATTACHED;
          if (isnewblk && lbn < NDADDR && fragoff(fs, diroffset) == 0) {
                  MALLOC(newdirblk, struct newdirblk *, sizeof(struct newdirblk),
                      M_NEWDIRBLK, M_SOFTDEP_FLAGS);
                  workitem_alloc(&newdirblk->db_list, D_NEWDIRBLK, mp);
          }
          if (newdirbp == NULL) {
                  dap->da_state |= DEPCOMPLETE;
                  ACQUIRE_LOCK(&lk);
          } else {
                  dap->da_state |= MKDIR_BODY | MKDIR_PARENT;
                  MALLOC(mkdir1, struct mkdir *, sizeof(struct mkdir), M_MKDIR,
                      M_SOFTDEP_FLAGS);
                  workitem_alloc(&mkdir1->md_list, D_MKDIR, mp);
                  mkdir1->md_state = MKDIR_BODY;
                  mkdir1->md_diradd = dap;
                  MALLOC(mkdir2, struct mkdir *, sizeof(struct mkdir), M_MKDIR,
                      M_SOFTDEP_FLAGS);
                  workitem_alloc(&mkdir2->md_list, D_MKDIR, mp);
                  mkdir2->md_state = MKDIR_PARENT;
                  mkdir2->md_diradd = dap;
                  /*
                   * Dependency on "." and ".." being written to disk.
                   */
                  mkdir1->md_buf = newdirbp;
                  ACQUIRE_LOCK(&lk);
                  LIST_INSERT_HEAD(&mkdirlisthd, mkdir1, md_mkdirs);
                  WORKLIST_INSERT(&newdirbp->b_dep, &mkdir1->md_list);
                  FREE_LOCK(&lk);
                  bdwrite(newdirbp);
                  /*
                   * Dependency on link count increase for parent directory
                   */
                  ACQUIRE_LOCK(&lk);
                  if (inodedep_lookup(mp, dp->i_number, 0, &inodedep) == 0
                      || (inodedep->id_state & ALLCOMPLETE) == ALLCOMPLETE) {
                          dap->da_state &= ~MKDIR_PARENT;
                          WORKITEM_FREE(mkdir2, D_MKDIR);
                  } else {
                          LIST_INSERT_HEAD(&mkdirlisthd, mkdir2, md_mkdirs);
                          WORKLIST_INSERT(&inodedep->id_bufwait,&mkdir2->md_list);
                  }
          }
          /*
           * Link into parent directory pagedep to await its being written.
           */
          if (pagedep_lookup(dp, lbn, DEPALLOC, &pagedep) == 0)
                  WORKLIST_INSERT(&bp->b_dep, &pagedep->pd_list);
          dap->da_pagedep = pagedep;
          LIST_INSERT_HEAD(&pagedep->pd_diraddhd[DIRADDHASH(offset)], dap,
              da_pdlist);
          /*
           * Link into its inodedep. Put it on the id_bufwait list if the inode
           * is not yet written. If it is written, do the post-inode write
           * processing to put it on the id_pendinghd list.
           */
          (void) inodedep_lookup(mp, newinum, DEPALLOC, &inodedep);
          if ((inodedep->id_state & ALLCOMPLETE) == ALLCOMPLETE)
                  diradd_inode_written(dap, inodedep);
          else
                  WORKLIST_INSERT(&inodedep->id_bufwait, &dap->da_list);
          if (isnewblk) {
                  /*
                   * Directories growing into indirect blocks are rare
                   * enough and the frequency of new block allocation
                   * in those cases even more rare, that we choose not
                   * to bother tracking them. Rather we simply force the
                   * new directory entry to disk.
                   */
                  if (lbn >= NDADDR) {
                          FREE_LOCK(&lk);
                          /*
                           * We only have a new allocation when at the
                           * beginning of a new block, not when we are
                           * expanding into an existing block.
                           */
                          if (blkoff(fs, diroffset) == 0)
                                  return (1);
                          return (0);
                  }
                  /*
                   * We only have a new allocation when at the beginning
                   * of a new fragment, not when we are expanding into an
                   * existing fragment. Also, there is nothing to do if we
                   * are already tracking this block.
                   */
                  if (fragoff(fs, diroffset) != 0) {
                          FREE_LOCK(&lk);
                          return (0);
                  }
                  if ((pagedep->pd_state & NEWBLOCK) != 0) {
                          WORKITEM_FREE(newdirblk, D_NEWDIRBLK);
                          FREE_LOCK(&lk);
                          return (0);
                  }
                  /*
                   * Find our associated allocdirect and have it track us.
                   */
                  if (inodedep_lookup(mp, dp->i_number, 0, &inodedep) == 0)
                          panic("softdep_setup_directory_add: lost inodedep");
                  adp = TAILQ_LAST(&inodedep->id_newinoupdt, allocdirectlst);
                  if (adp == NULL || adp->ad_lbn != lbn)
                          panic("softdep_setup_directory_add: lost entry");
                  pagedep->pd_state |= NEWBLOCK;
                  newdirblk->db_pagedep = pagedep;
                  WORKLIST_INSERT(&adp->ad_newdirblk, &newdirblk->db_list);
          }
          FREE_LOCK(&lk);
          return (0);
  }
  
  /*
   * This procedure is called to change the offset of a directory
   * entry when compacting a directory block which must be owned
   * exclusively by the caller. Note that the actual entry movement
   * must be done in this procedure to ensure that no I/O completions
   * occur while the move is in progress.
   */
  void 
  softdep_change_directoryentry_offset(dp, base, oldloc, newloc, entrysize)
          struct inode *dp;       /* inode for directory */
          caddr_t base;           /* address of dp->i_offset */
          caddr_t oldloc;         /* address of old directory location */
          caddr_t newloc;         /* address of new directory location */
          int entrysize;          /* size of directory entry */
  {
          int offset, oldoffset, newoffset;
          struct pagedep *pagedep;
          struct diradd *dap;
          ufs_lbn_t lbn;
  
          ACQUIRE_LOCK(&lk);
          lbn = lblkno(dp->i_fs, dp->i_offset);
          offset = blkoff(dp->i_fs, dp->i_offset);
          if (pagedep_lookup(dp, lbn, 0, &pagedep) == 0)
                  goto done;
          oldoffset = offset + (oldloc - base);
          newoffset = offset + (newloc - base);
  
          LIST_FOREACH(dap, &pagedep->pd_diraddhd[DIRADDHASH(oldoffset)], da_pdlist) {
                  if (dap->da_offset != oldoffset)
                          continue;
                  dap->da_offset = newoffset;
                  if (DIRADDHASH(newoffset) == DIRADDHASH(oldoffset))
                          break;
                  LIST_REMOVE(dap, da_pdlist);
                  LIST_INSERT_HEAD(&pagedep->pd_diraddhd[DIRADDHASH(newoffset)],
                      dap, da_pdlist);
                  break;
          }
          if (dap == NULL) {
  
                  LIST_FOREACH(dap, &pagedep->pd_pendinghd, da_pdlist) {
                          if (dap->da_offset == oldoffset) {
                                  dap->da_offset = newoffset;
                                  break;
                          }
                  }
          }
  done:
          bcopy(oldloc, newloc, entrysize);
          FREE_LOCK(&lk);
  }
  
  /*
   * Free a diradd dependency structure. This routine must be called
   * with splbio interrupts blocked.
   */
  static void
  free_diradd(dap)
          struct diradd *dap;
  {
          struct dirrem *dirrem;
          struct pagedep *pagedep;
          struct inodedep *inodedep;
          struct mkdir *mkdir, *nextmd;
  
          mtx_assert(&lk, MA_OWNED);
          WORKLIST_REMOVE(&dap->da_list);
          LIST_REMOVE(dap, da_pdlist);
          if ((dap->da_state & DIRCHG) == 0) {
                  pagedep = dap->da_pagedep;
          } else {
                  dirrem = dap->da_previous;
                  pagedep = dirrem->dm_pagedep;
                  dirrem->dm_dirinum = pagedep->pd_ino;
                  add_to_worklist(&dirrem->dm_list);
          }
          if (inodedep_lookup(pagedep->pd_list.wk_mp, dap->da_newinum,
              0, &inodedep) != 0)
                  (void) free_inodedep(inodedep);
          if ((dap->da_state & (MKDIR_PARENT | MKDIR_BODY)) != 0) {
                  for (mkdir = LIST_FIRST(&mkdirlisthd); mkdir; mkdir = nextmd) {
                          nextmd = LIST_NEXT(mkdir, md_mkdirs);
                          if (mkdir->md_diradd != dap)
                                  continue;
                          dap->da_state &= ~mkdir->md_state;
                          WORKLIST_REMOVE(&mkdir->md_list);
                          LIST_REMOVE(mkdir, md_mkdirs);
                          WORKITEM_FREE(mkdir, D_MKDIR);
                  }
                  if ((dap->da_state & (MKDIR_PARENT | MKDIR_BODY)) != 0)
                          panic("free_diradd: unfound ref");
          }
          WORKITEM_FREE(dap, D_DIRADD);
  }
  
  /*
   * Directory entry removal dependencies.
   * 
   * When removing a directory entry, the entry's inode pointer must be
   * zero'ed on disk before the corresponding inode's link count is decremented
   * (possibly freeing the inode for re-use). This dependency is handled by
   * updating the directory entry but delaying the inode count reduction until
   * after the directory block has been written to disk. After this point, the
   * inode count can be decremented whenever it is convenient.
   */
  
  /*
   * This routine should be called immediately after removing
   * a directory entry.  The inode's link count should not be
   * decremented by the calling procedure -- the soft updates
   * code will do this task when it is safe.
   */
  void 
  softdep_setup_remove(bp, dp, ip, isrmdir)
          struct buf *bp;         /* buffer containing directory block */
          struct inode *dp;       /* inode for the directory being modified */
          struct inode *ip;       /* inode for directory entry being removed */
          int isrmdir;            /* indicates if doing RMDIR */
  {
          struct dirrem *dirrem, *prevdirrem;
  
          /*
           * Allocate a new dirrem if appropriate and ACQUIRE_LOCK.
           */
          dirrem = newdirrem(bp, dp, ip, isrmdir, &prevdirrem);
  
          /*
           * If the COMPLETE flag is clear, then there were no active
           * entries and we want to roll back to a zeroed entry until
           * the new inode is committed to disk. If the COMPLETE flag is
           * set then we have deleted an entry that never made it to
           * disk. If the entry we deleted resulted from a name change,
           * then the old name still resides on disk. We cannot delete
           * its inode (returned to us in prevdirrem) until the zeroed
           * directory entry gets to disk. The new inode has never been
           * referenced on the disk, so can be deleted immediately.
           */
          if ((dirrem->dm_state & COMPLETE) == 0) {
                  LIST_INSERT_HEAD(&dirrem->dm_pagedep->pd_dirremhd, dirrem,
                      dm_next);
                  FREE_LOCK(&lk);
          } else {
                  if (prevdirrem != NULL)
                          LIST_INSERT_HEAD(&dirrem->dm_pagedep->pd_dirremhd,
                              prevdirrem, dm_next);
                  dirrem->dm_dirinum = dirrem->dm_pagedep->pd_ino;
                  FREE_LOCK(&lk);
                  handle_workitem_remove(dirrem, NULL);
          }
  }
  
  /*
   * Allocate a new dirrem if appropriate and return it along with
   * its associated pagedep. Called without a lock, returns with lock.
   */
  static long num_dirrem;         /* number of dirrem allocated */
  static struct dirrem *
  newdirrem(bp, dp, ip, isrmdir, prevdirremp)
          struct buf *bp;         /* buffer containing directory block */
          struct inode *dp;       /* inode for the directory being modified */
          struct inode *ip;       /* inode for directory entry being removed */
          int isrmdir;            /* indicates if doing RMDIR */
          struct dirrem **prevdirremp; /* previously referenced inode, if any */
  {
          int offset;
          ufs_lbn_t lbn;
          struct diradd *dap;
          struct dirrem *dirrem;
          struct pagedep *pagedep;
  
          /*
           * Whiteouts have no deletion dependencies.
           */
          if (ip == NULL)
                  panic("newdirrem: whiteout");
          /*
           * If we are over our limit, try to improve the situation.
           * Limiting the number of dirrem structures will also limit
           * the number of freefile and freeblks structures.
           */
          ACQUIRE_LOCK(&lk);
          if (num_dirrem > max_softdeps / 2)
                  (void) request_cleanup(ITOV(dp)->v_mount, FLUSH_REMOVE);
          num_dirrem += 1;
          FREE_LOCK(&lk);
          MALLOC(dirrem, struct dirrem *, sizeof(struct dirrem),
                  M_DIRREM, M_SOFTDEP_FLAGS|M_ZERO);
          workitem_alloc(&dirrem->dm_list, D_DIRREM, ITOV(dp)->v_mount);
          dirrem->dm_state = isrmdir ? RMDIR : 0;
          dirrem->dm_oldinum = ip->i_number;
          *prevdirremp = NULL;
  
          ACQUIRE_LOCK(&lk);
          lbn = lblkno(dp->i_fs, dp->i_offset);
          offset = blkoff(dp->i_fs, dp->i_offset);
          if (pagedep_lookup(dp, lbn, DEPALLOC, &pagedep) == 0)
                  WORKLIST_INSERT(&bp->b_dep, &pagedep->pd_list);
          dirrem->dm_pagedep = pagedep;
          /*
           * Check for a diradd dependency for the same directory entry.
           * If present, then both dependencies become obsolete and can
           * be de-allocated. Check for an entry on both the pd_dirraddhd
           * list and the pd_pendinghd list.
           */
  
          LIST_FOREACH(dap, &pagedep->pd_diraddhd[DIRADDHASH(offset)], da_pdlist)
                  if (dap->da_offset == offset)
                          break;
          if (dap == NULL) {
  
                  LIST_FOREACH(dap, &pagedep->pd_pendinghd, da_pdlist)
                          if (dap->da_offset == offset)
                                  break;
                  if (dap == NULL)
                          return (dirrem);
          }
          /*
           * Must be ATTACHED at this point.
           */
          if ((dap->da_state & ATTACHED) == 0)
                  panic("newdirrem: not ATTACHED");
          if (dap->da_newinum != ip->i_number)
                  panic("newdirrem: inum %d should be %d",
                      ip->i_number, dap->da_newinum);
          /*
           * If we are deleting a changed name that never made it to disk,
           * then return the dirrem describing the previous inode (which
           * represents the inode currently referenced from this entry on disk).
           */
          if ((dap->da_state & DIRCHG) != 0) {
                  *prevdirremp = dap->da_previous;
                  dap->da_state &= ~DIRCHG;
                  dap->da_pagedep = pagedep;
          }
          /*
           * We are deleting an entry that never made it to disk.
           * Mark it COMPLETE so we can delete its inode immediately.
           */
          dirrem->dm_state |= COMPLETE;
          free_diradd(dap);
          return (dirrem);
  }
  
  /*
   * Directory entry change dependencies.
   * 
   * Changing an existing directory entry requires that an add operation
   * be completed first followed by a deletion. The semantics for the addition
   * are identical to the description of adding a new entry above except
   * that the rollback is to the old inode number rather than zero. Once
   * the addition dependency is completed, the removal is done as described
   * in the removal routine above.
   */
  
  /*
   * This routine should be called immediately after changing
   * a directory entry.  The inode's link count should not be
   * decremented by the calling procedure -- the soft updates
   * code will perform this task when it is safe.
   */
  void 
  softdep_setup_directory_change(bp, dp, ip, newinum, isrmdir)
          struct buf *bp;         /* buffer containing directory block */
          struct inode *dp;       /* inode for the directory being modified */
          struct inode *ip;       /* inode for directory entry being removed */
          ino_t newinum;          /* new inode number for changed entry */
          int isrmdir;            /* indicates if doing RMDIR */
  {
          int offset;
          struct diradd *dap = NULL;
          struct dirrem *dirrem, *prevdirrem;
          struct pagedep *pagedep;
          struct inodedep *inodedep;
          struct mount *mp;
  
          offset = blkoff(dp->i_fs, dp->i_offset);
          mp = UFSTOVFS(dp->i_ump);
  
          /*
           * Whiteouts do not need diradd dependencies.
           */
          if (newinum != WINO) {
                  MALLOC(dap, struct diradd *, sizeof(struct diradd),
                      M_DIRADD, M_SOFTDEP_FLAGS|M_ZERO);
                  workitem_alloc(&dap->da_list, D_DIRADD, mp);
                  dap->da_state = DIRCHG | ATTACHED | DEPCOMPLETE;
                  dap->da_offset = offset;
                  dap->da_newinum = newinum;
          }
  
          /*
           * Allocate a new dirrem and ACQUIRE_LOCK.
           */
          dirrem = newdirrem(bp, dp, ip, isrmdir, &prevdirrem);
          pagedep = dirrem->dm_pagedep;
          /*
           * The possible values for isrmdir:
           *      0 - non-directory file rename
           *      1 - directory rename within same directory
           *   inum - directory rename to new directory of given inode number
           * When renaming to a new directory, we are both deleting and
           * creating a new directory entry, so the link count on the new
           * directory should not change. Thus we do not need the followup
           * dirrem which is usually done in handle_workitem_remove. We set
           * the DIRCHG flag to tell handle_workitem_remove to skip the 
           * followup dirrem.
           */
          if (isrmdir > 1)
                  dirrem->dm_state |= DIRCHG;
  
          /*
           * Whiteouts have no additional dependencies,
           * so just put the dirrem on the correct list.
           */
          if (newinum == WINO) {
                  if ((dirrem->dm_state & COMPLETE) == 0) {
                          LIST_INSERT_HEAD(&pagedep->pd_dirremhd, dirrem,
                              dm_next);
                  } else {
                          dirrem->dm_dirinum = pagedep->pd_ino;
                          add_to_worklist(&dirrem->dm_list);
                  }
                  FREE_LOCK(&lk);
                  return;
          }
  
          /*
           * If the COMPLETE flag is clear, then there were no active
           * entries and we want to roll back to the previous inode until
           * the new inode is committed to disk. If the COMPLETE flag is
           * set, then we have deleted an entry that never made it to disk.
           * If the entry we deleted resulted from a name change, then the old
           * inode reference still resides on disk. Any rollback that we do
           * needs to be to that old inode (returned to us in prevdirrem). If
           * the entry we deleted resulted from a create, then there is
           * no entry on the disk, so we want to roll back to zero rather
           * than the uncommitted inode. In either of the COMPLETE cases we
           * want to immediately free the unwritten and unreferenced inode.
           */
          if ((dirrem->dm_state & COMPLETE) == 0) {
                  dap->da_previous = dirrem;
          } else {
                  if (prevdirrem != NULL) {
                          dap->da_previous = prevdirrem;
                  } else {
                          dap->da_state &= ~DIRCHG;
                          dap->da_pagedep = pagedep;
                  }
                  dirrem->dm_dirinum = pagedep->pd_ino;
                  add_to_worklist(&dirrem->dm_list);
          }
          /*
           * Link into its inodedep. Put it on the id_bufwait list if the inode
           * is not yet written. If it is written, do the post-inode write
           * processing to put it on the id_pendinghd list.
           */
          if (inodedep_lookup(mp, newinum, DEPALLOC, &inodedep) == 0 ||
              (inodedep->id_state & ALLCOMPLETE) == ALLCOMPLETE) {
                  dap->da_state |= COMPLETE;
                  LIST_INSERT_HEAD(&pagedep->pd_pendinghd, dap, da_pdlist);
                  WORKLIST_INSERT(&inodedep->id_pendinghd, &dap->da_list);
          } else {
                  LIST_INSERT_HEAD(&pagedep->pd_diraddhd[DIRADDHASH(offset)],
                      dap, da_pdlist);
                  WORKLIST_INSERT(&inodedep->id_bufwait, &dap->da_list);
          }
          FREE_LOCK(&lk);
  }
  
  /*
   * Called whenever the link count on an inode is changed.
   * It creates an inode dependency so that the new reference(s)
   * to the inode cannot be committed to disk until the updated
   * inode has been written.
   */
  void
  softdep_change_linkcnt(ip)
          struct inode *ip;       /* the inode with the increased link count */
  {
          struct inodedep *inodedep;
  
          ACQUIRE_LOCK(&lk);
          (void) inodedep_lookup(UFSTOVFS(ip->i_ump), ip->i_number,
              DEPALLOC, &inodedep);
          if (ip->i_nlink < ip->i_effnlink)
                  panic("softdep_change_linkcnt: bad delta");
          inodedep->id_nlinkdelta = ip->i_nlink - ip->i_effnlink;
          FREE_LOCK(&lk);
  }
  
  /*
   * Called when the effective link count and the reference count
   * on an inode drops to zero. At this point there are no names
   * referencing the file in the filesystem and no active file
   * references. The space associated with the file will be freed
   * as soon as the necessary soft dependencies are cleared.
   */
  void
  softdep_releasefile(ip)
          struct inode *ip;       /* inode with the zero effective link count */
  {
          struct inodedep *inodedep;
          struct fs *fs;
          int extblocks;
  
          if (ip->i_effnlink > 0)
                  panic("softdep_releasefile: file still referenced");
          /*
           * We may be called several times as the on-disk link count
           * drops to zero. We only want to account for the space once.
           */
          if (ip->i_flag & IN_SPACECOUNTED)
                  return;
          /*
           * We have to deactivate a snapshot otherwise copyonwrites may
           * add blocks and the cleanup may remove blocks after we have
           * tried to account for them.
           */
          if ((ip->i_flags & SF_SNAPSHOT) != 0)
                  ffs_snapremove(ITOV(ip));
          /*
           * If we are tracking an nlinkdelta, we have to also remember
           * whether we accounted for the freed space yet.
           */
          ACQUIRE_LOCK(&lk);
          if ((inodedep_lookup(UFSTOVFS(ip->i_ump), ip->i_number, 0, &inodedep)))
                  inodedep->id_state |= SPACECOUNTED;
          FREE_LOCK(&lk);
          fs = ip->i_fs;
          extblocks = 0;
          if (fs->fs_magic == FS_UFS2_MAGIC)
                  extblocks = btodb(fragroundup(fs, ip->i_din2->di_extsize));
          UFS_LOCK(ip->i_ump);
          ip->i_fs->fs_pendingblocks += DIP(ip, i_blocks) - extblocks;
          ip->i_fs->fs_pendinginodes += 1;
          UFS_UNLOCK(ip->i_ump);
          ip->i_flag |= IN_SPACECOUNTED;
  }
  
  /*
   * This workitem decrements the inode's link count.
   * If the link count reaches zero, the file is removed.
   */
  static void 
  handle_workitem_remove(dirrem, xp)
          struct dirrem *dirrem;
          struct vnode *xp;
  {
          struct thread *td = curthread;
          struct inodedep *inodedep;
          struct vnode *vp;
          struct inode *ip;
          ino_t oldinum;
          int error;
  
          if ((vp = xp) == NULL &&
              (error = ffs_vget(dirrem->dm_list.wk_mp,
              dirrem->dm_oldinum, LK_EXCLUSIVE, &vp)) != 0) {
                  softdep_error("handle_workitem_remove: vget", error);
                  return;
          }
          ip = VTOI(vp);
          ACQUIRE_LOCK(&lk);
          if ((inodedep_lookup(dirrem->dm_list.wk_mp,
              dirrem->dm_oldinum, 0, &inodedep)) == 0)
                  panic("handle_workitem_remove: lost inodedep");
          /*
           * Normal file deletion.
           */
          if ((dirrem->dm_state & RMDIR) == 0) {
                  ip->i_nlink--;
                  DIP_SET(ip, i_nlink, ip->i_nlink);
                  ip->i_flag |= IN_CHANGE;
                  if (ip->i_nlink < ip->i_effnlink)
                          panic("handle_workitem_remove: bad file delta");
                  inodedep->id_nlinkdelta = ip->i_nlink - ip->i_effnlink;
                  num_dirrem -= 1;
                  WORKITEM_FREE(dirrem, D_DIRREM);
                  FREE_LOCK(&lk);
                  vput(vp);
                  return;
          }
          /*
           * Directory deletion. Decrement reference count for both the
           * just deleted parent directory entry and the reference for ".".
           * Next truncate the directory to length zero. When the
           * truncation completes, arrange to have the reference count on
           * the parent decremented to account for the loss of "..".
           */
          ip->i_nlink -= 2;
          DIP_SET(ip, i_nlink, ip->i_nlink);
          ip->i_flag |= IN_CHANGE;
          if (ip->i_nlink < ip->i_effnlink)
                  panic("handle_workitem_remove: bad dir delta");
          inodedep->id_nlinkdelta = ip->i_nlink - ip->i_effnlink;
          FREE_LOCK(&lk);
          if ((error = ffs_truncate(vp, (off_t)0, 0, td->td_ucred, td)) != 0)
                  softdep_error("handle_workitem_remove: truncate", error);
          ACQUIRE_LOCK(&lk);
          /*
           * Rename a directory to a new parent. Since, we are both deleting
           * and creating a new directory entry, the link count on the new
           * directory should not change. Thus we skip the followup dirrem.
           */
          if (dirrem->dm_state & DIRCHG) {
                  num_dirrem -= 1;
                  WORKITEM_FREE(dirrem, D_DIRREM);
                  FREE_LOCK(&lk);
                  vput(vp);
                  return;
          }
          /*
           * If the inodedep does not exist, then the zero'ed inode has
           * been written to disk. If the allocated inode has never been
           * written to disk, then the on-disk inode is zero'ed. In either
           * case we can remove the file immediately.
           */
          dirrem->dm_state = 0;
          oldinum = dirrem->dm_oldinum;
          dirrem->dm_oldinum = dirrem->dm_dirinum;
          if (inodedep_lookup(dirrem->dm_list.wk_mp, oldinum,
              0, &inodedep) == 0 || check_inode_unwritten(inodedep)) {
                  if (xp != NULL)
                          add_to_worklist(&dirrem->dm_list);
                  FREE_LOCK(&lk);
                  vput(vp);
                  if (xp == NULL)
                          handle_workitem_remove(dirrem, NULL);
                  return;
          }
          WORKLIST_INSERT(&inodedep->id_inowait, &dirrem->dm_list);
          FREE_LOCK(&lk);
          ip->i_flag |= IN_CHANGE;
          ffs_update(vp, 0);
          vput(vp);
  }
  
  /*
   * Inode de-allocation dependencies.
   * 
   * When an inode's link count is reduced to zero, it can be de-allocated. We
   * found it convenient to postpone de-allocation until after the inode is
   * written to disk with its new link count (zero).  At this point, all of the
   * on-disk inode's block pointers are nullified and, with careful dependency
   * list ordering, all dependencies related to the inode will be satisfied and
   * the corresponding dependency structures de-allocated.  So, if/when the
   * inode is reused, there will be no mixing of old dependencies with new
   * ones.  This artificial dependency is set up by the block de-allocation
   * procedure above (softdep_setup_freeblocks) and completed by the
   * following procedure.
   */
  static void 
  handle_workitem_freefile(freefile)
          struct freefile *freefile;
  {
          struct fs *fs;
          struct inodedep *idp;
          struct ufsmount *ump;
          int error;
  
          ump = VFSTOUFS(freefile->fx_list.wk_mp);
          fs = ump->um_fs;
  #ifdef DEBUG
          ACQUIRE_LOCK(&lk);
          error = inodedep_lookup(UFSTOVFS(ump), freefile->fx_oldinum, 0, &idp);
          FREE_LOCK(&lk);
          if (error)
                  panic("handle_workitem_freefile: inodedep survived");
  #endif
          UFS_LOCK(ump);
          fs->fs_pendinginodes -= 1;
          UFS_UNLOCK(ump);
          if ((error = ffs_freefile(ump, fs, freefile->fx_devvp,
              freefile->fx_oldinum, freefile->fx_mode)) != 0)
                  softdep_error("handle_workitem_freefile", error);
          ACQUIRE_LOCK(&lk);
          WORKITEM_FREE(freefile, D_FREEFILE);
          FREE_LOCK(&lk);
  }
  
  
  /*
   * Helper function which unlinks marker element from work list and returns
   * the next element on the list.
   */
  static __inline struct worklist *
  markernext(struct worklist *marker)
  {
          struct worklist *next;
          
          next = LIST_NEXT(marker, wk_list);
          LIST_REMOVE(marker, wk_list);
          return next;
  }
  
  /*
   * Disk writes.
   * 
   * The dependency structures constructed above are most actively used when file
   * system blocks are written to disk.  No constraints are placed on when a
   * block can be written, but unsatisfied update dependencies are made safe by
   * modifying (or replacing) the source memory for the duration of the disk
   * write.  When the disk write completes, the memory block is again brought
   * up-to-date.
   *
   * In-core inode structure reclamation.
   * 
   * Because there are a finite number of "in-core" inode structures, they are
   * reused regularly.  By transferring all inode-related dependencies to the
   * in-memory inode block and indexing them separately (via "inodedep"s), we
   * can allow "in-core" inode structures to be reused at any time and avoid
   * any increase in contention.
   *
   * Called just before entering the device driver to initiate a new disk I/O.
   * The buffer must be locked, thus, no I/O completion operations can occur
   * while we are manipulating its associated dependencies.
   */
  static void 
  softdep_disk_io_initiation(bp)
          struct buf *bp;         /* structure describing disk write to occur */
  {
          struct worklist *wk;
          struct worklist marker;
          struct indirdep *indirdep;
          struct inodedep *inodedep;
  
          /*
           * We only care about write operations. There should never
           * be dependencies for reads.
           */
          if (bp->b_iocmd != BIO_WRITE)
                  panic("softdep_disk_io_initiation: not write");
  
          marker.wk_type = D_LAST + 1;    /* Not a normal workitem */
          PHOLD(curproc);                 /* Don't swap out kernel stack */
  
          ACQUIRE_LOCK(&lk);
          /*
           * Do any necessary pre-I/O processing.
           */
          for (wk = LIST_FIRST(&bp->b_dep); wk != NULL;
               wk = markernext(&marker)) {
                  LIST_INSERT_AFTER(wk, &marker, wk_list);
                  switch (wk->wk_type) {
  
                  case D_PAGEDEP:
                          initiate_write_filepage(WK_PAGEDEP(wk), bp);
                          continue;
  
                  case D_INODEDEP:
                          inodedep = WK_INODEDEP(wk);
                          if (inodedep->id_fs->fs_magic == FS_UFS1_MAGIC)
                                  initiate_write_inodeblock_ufs1(inodedep, bp);
                          else
                                  initiate_write_inodeblock_ufs2(inodedep, bp);
                          continue;
  
                  case D_INDIRDEP:
                          indirdep = WK_INDIRDEP(wk);
                          if (indirdep->ir_state & GOINGAWAY)
                                  panic("disk_io_initiation: indirdep gone");
                          /*
                           * If there are no remaining dependencies, this
                           * will be writing the real pointers, so the
                           * dependency can be freed.
                           */
                          if (LIST_EMPTY(&indirdep->ir_deplisthd)) {
                                  struct buf *bp;
  
                                  bp = indirdep->ir_savebp;
                                  bp->b_flags |= B_INVAL | B_NOCACHE;
                                  /* inline expand WORKLIST_REMOVE(wk); */
                                  wk->wk_state &= ~ONWORKLIST;
                                  LIST_REMOVE(wk, wk_list);
                                  WORKITEM_FREE(indirdep, D_INDIRDEP);
                                  FREE_LOCK(&lk);
                                  brelse(bp);
                                  ACQUIRE_LOCK(&lk);
                                  continue;
                          }
                          /*
                           * Replace up-to-date version with safe version.
                           */
                          FREE_LOCK(&lk);
                          MALLOC(indirdep->ir_saveddata, caddr_t, bp->b_bcount,
                              M_INDIRDEP, M_SOFTDEP_FLAGS);
                          ACQUIRE_LOCK(&lk);
                          indirdep->ir_state &= ~ATTACHED;
                          indirdep->ir_state |= UNDONE;
                          bcopy(bp->b_data, indirdep->ir_saveddata, bp->b_bcount);
                          bcopy(indirdep->ir_savebp->b_data, bp->b_data,
                              bp->b_bcount);
                          continue;
  
                  case D_MKDIR:
                  case D_BMSAFEMAP:
                  case D_ALLOCDIRECT:
                  case D_ALLOCINDIR:
                          continue;
  
                  default:
                          panic("handle_disk_io_initiation: Unexpected type %s",
                              TYPENAME(wk->wk_type));
                          /* NOTREACHED */
                  }
          }
          FREE_LOCK(&lk);
          PRELE(curproc);                 /* Allow swapout of kernel stack */
  }
  
  /*
   * Called from within the procedure above to deal with unsatisfied
   * allocation dependencies in a directory. The buffer must be locked,
   * thus, no I/O completion operations can occur while we are
   * manipulating its associated dependencies.
   */
  static void
  initiate_write_filepage(pagedep, bp)
          struct pagedep *pagedep;
          struct buf *bp;
  {
          struct diradd *dap;
          struct direct *ep;
          int i;
  
          if (pagedep->pd_state & IOSTARTED) {
                  /*
                   * This can only happen if there is a driver that does not
                   * understand chaining. Here biodone will reissue the call
                   * to strategy for the incomplete buffers.
                   */
                  printf("initiate_write_filepage: already started\n");
                  return;
          }
          pagedep->pd_state |= IOSTARTED;
          for (i = 0; i < DAHASHSZ; i++) {
                  LIST_FOREACH(dap, &pagedep->pd_diraddhd[i], da_pdlist) {
                          ep = (struct direct *)
                              ((char *)bp->b_data + dap->da_offset);
                          if (ep->d_ino != dap->da_newinum)
                                  panic("%s: dir inum %d != new %d",
                                      "initiate_write_filepage",
                                      ep->d_ino, dap->da_newinum);
                          if (dap->da_state & DIRCHG)
                                  ep->d_ino = dap->da_previous->dm_oldinum;
                          else
                                  ep->d_ino = 0;
                          dap->da_state &= ~ATTACHED;
                          dap->da_state |= UNDONE;
                  }
          }
  }
  
  /*
   * Version of initiate_write_inodeblock that handles UFS1 dinodes.
   * Note that any bug fixes made to this routine must be done in the
   * version found below.
   *
   * Called from within the procedure above to deal with unsatisfied
   * allocation dependencies in an inodeblock. The buffer must be
   * locked, thus, no I/O completion operations can occur while we
   * are manipulating its associated dependencies.
   */
  static void 
  initiate_write_inodeblock_ufs1(inodedep, bp)
          struct inodedep *inodedep;
          struct buf *bp;                 /* The inode block */
  {
          struct allocdirect *adp, *lastadp;
          struct ufs1_dinode *dp;
          struct ufs1_dinode *sip;
          struct fs *fs;
          ufs_lbn_t i;
  #ifdef INVARIANTS
          ufs_lbn_t prevlbn = 0;
  #endif
          int deplist;
  
          if (inodedep->id_state & IOSTARTED)
                  panic("initiate_write_inodeblock_ufs1: already started");
          inodedep->id_state |= IOSTARTED;
          fs = inodedep->id_fs;
          dp = (struct ufs1_dinode *)bp->b_data +
              ino_to_fsbo(fs, inodedep->id_ino);
          /*
           * If the bitmap is not yet written, then the allocated
           * inode cannot be written to disk.
           */
          if ((inodedep->id_state & DEPCOMPLETE) == 0) {
                  if (inodedep->id_savedino1 != NULL)
                          panic("initiate_write_inodeblock_ufs1: I/O underway");
                  FREE_LOCK(&lk);
                  MALLOC(sip, struct ufs1_dinode *,
                      sizeof(struct ufs1_dinode), M_SAVEDINO, M_SOFTDEP_FLAGS);
                  ACQUIRE_LOCK(&lk);
                  inodedep->id_savedino1 = sip;
                  *inodedep->id_savedino1 = *dp;
                  bzero((caddr_t)dp, sizeof(struct ufs1_dinode));
                  dp->di_gen = inodedep->id_savedino1->di_gen;
                  return;
          }
          /*
           * If no dependencies, then there is nothing to roll back.
           */
          inodedep->id_savedsize = dp->di_size;
          inodedep->id_savedextsize = 0;
          if (TAILQ_EMPTY(&inodedep->id_inoupdt))
                  return;
          /*
           * Set the dependencies to busy.
           */
          for (deplist = 0, adp = TAILQ_FIRST(&inodedep->id_inoupdt); adp;
               adp = TAILQ_NEXT(adp, ad_next)) {
  #ifdef INVARIANTS
                  if (deplist != 0 && prevlbn >= adp->ad_lbn)
                          panic("softdep_write_inodeblock: lbn order");
                  prevlbn = adp->ad_lbn;
                  if (adp->ad_lbn < NDADDR &&
                      dp->di_db[adp->ad_lbn] != adp->ad_newblkno)
                          panic("%s: direct pointer #%jd mismatch %d != %jd",
                              "softdep_write_inodeblock",
                              (intmax_t)adp->ad_lbn,
                              dp->di_db[adp->ad_lbn],
                              (intmax_t)adp->ad_newblkno);
                  if (adp->ad_lbn >= NDADDR &&
                      dp->di_ib[adp->ad_lbn - NDADDR] != adp->ad_newblkno)
                          panic("%s: indirect pointer #%jd mismatch %d != %jd",
                              "softdep_write_inodeblock",
                              (intmax_t)adp->ad_lbn - NDADDR,
                              dp->di_ib[adp->ad_lbn - NDADDR],
                              (intmax_t)adp->ad_newblkno);
                  deplist |= 1 << adp->ad_lbn;
                  if ((adp->ad_state & ATTACHED) == 0)
                          panic("softdep_write_inodeblock: Unknown state 0x%x",
                              adp->ad_state);
  #endif /* INVARIANTS */
                  adp->ad_state &= ~ATTACHED;
                  adp->ad_state |= UNDONE;
          }
          /*
           * The on-disk inode cannot claim to be any larger than the last
           * fragment that has been written. Otherwise, the on-disk inode
           * might have fragments that were not the last block in the file
           * which would corrupt the filesystem.
           */
          for (lastadp = NULL, adp = TAILQ_FIRST(&inodedep->id_inoupdt); adp;
               lastadp = adp, adp = TAILQ_NEXT(adp, ad_next)) {
                  if (adp->ad_lbn >= NDADDR)
                          break;
                  dp->di_db[adp->ad_lbn] = adp->ad_oldblkno;
                  /* keep going until hitting a rollback to a frag */
                  if (adp->ad_oldsize == 0 || adp->ad_oldsize == fs->fs_bsize)
                          continue;
                  dp->di_size = fs->fs_bsize * adp->ad_lbn + adp->ad_oldsize;
                  for (i = adp->ad_lbn + 1; i < NDADDR; i++) {
  #ifdef INVARIANTS
                          if (dp->di_db[i] != 0 && (deplist & (1 << i)) == 0)
                                  panic("softdep_write_inodeblock: lost dep1");
  #endif /* INVARIANTS */
                          dp->di_db[i] = 0;
                  }
                  for (i = 0; i < NIADDR; i++) {
  #ifdef INVARIANTS
                          if (dp->di_ib[i] != 0 &&
                              (deplist & ((1 << NDADDR) << i)) == 0)
                                  panic("softdep_write_inodeblock: lost dep2");
  #endif /* INVARIANTS */
                          dp->di_ib[i] = 0;
                  }
                  return;
          }
          /*
           * If we have zero'ed out the last allocated block of the file,
           * roll back the size to the last currently allocated block.
           * We know that this last allocated block is a full-sized as
           * we already checked for fragments in the loop above.
           */
          if (lastadp != NULL &&
              dp->di_size <= (lastadp->ad_lbn + 1) * fs->fs_bsize) {
                  for (i = lastadp->ad_lbn; i >= 0; i--)
                          if (dp->di_db[i] != 0)
                                  break;
                  dp->di_size = (i + 1) * fs->fs_bsize;
          }
          /*
           * The only dependencies are for indirect blocks.
           *
           * The file size for indirect block additions is not guaranteed.
           * Such a guarantee would be non-trivial to achieve. The conventional
           * synchronous write implementation also does not make this guarantee.
           * Fsck should catch and fix discrepancies. Arguably, the file size
           * can be over-estimated without destroying integrity when the file
           * moves into the indirect blocks (i.e., is large). If we want to
           * postpone fsck, we are stuck with this argument.
           */
          for (; adp; adp = TAILQ_NEXT(adp, ad_next))
                  dp->di_ib[adp->ad_lbn - NDADDR] = 0;
  }
                  
  /*
   * Version of initiate_write_inodeblock that handles UFS2 dinodes.
   * Note that any bug fixes made to this routine must be done in the
   * version found above.
   *
   * Called from within the procedure above to deal with unsatisfied
   * allocation dependencies in an inodeblock. The buffer must be
   * locked, thus, no I/O completion operations can occur while we
   * are manipulating its associated dependencies.
   */
  static void 
  initiate_write_inodeblock_ufs2(inodedep, bp)
          struct inodedep *inodedep;
          struct buf *bp;                 /* The inode block */
  {
          struct allocdirect *adp, *lastadp;
          struct ufs2_dinode *dp;
          struct ufs2_dinode *sip;
          struct fs *fs;
          ufs_lbn_t i;
  #ifdef INVARIANTS
          ufs_lbn_t prevlbn = 0;
  #endif
          int deplist;
  
          if (inodedep->id_state & IOSTARTED)
                  panic("initiate_write_inodeblock_ufs2: already started");
          inodedep->id_state |= IOSTARTED;
          fs = inodedep->id_fs;
          dp = (struct ufs2_dinode *)bp->b_data +
              ino_to_fsbo(fs, inodedep->id_ino);
          /*
           * If the bitmap is not yet written, then the allocated
           * inode cannot be written to disk.
           */
          if ((inodedep->id_state & DEPCOMPLETE) == 0) {
                  if (inodedep->id_savedino2 != NULL)
                          panic("initiate_write_inodeblock_ufs2: I/O underway");
                  FREE_LOCK(&lk);
                  MALLOC(sip, struct ufs2_dinode *,
                      sizeof(struct ufs2_dinode), M_SAVEDINO, M_SOFTDEP_FLAGS);
                  ACQUIRE_LOCK(&lk);
                  inodedep->id_savedino2 = sip;
                  *inodedep->id_savedino2 = *dp;
                  bzero((caddr_t)dp, sizeof(struct ufs2_dinode));
                  dp->di_gen = inodedep->id_savedino2->di_gen;
                  return;
          }
          /*
           * If no dependencies, then there is nothing to roll back.
           */
          inodedep->id_savedsize = dp->di_size;
          inodedep->id_savedextsize = dp->di_extsize;
          if (TAILQ_EMPTY(&inodedep->id_inoupdt) &&
              TAILQ_EMPTY(&inodedep->id_extupdt))
                  return;
          /*
           * Set the ext data dependencies to busy.
           */
          for (deplist = 0, adp = TAILQ_FIRST(&inodedep->id_extupdt); adp;
               adp = TAILQ_NEXT(adp, ad_next)) {
  #ifdef INVARIANTS
                  if (deplist != 0 && prevlbn >= adp->ad_lbn)
                          panic("softdep_write_inodeblock: lbn order");
                  prevlbn = adp->ad_lbn;
                  if (dp->di_extb[adp->ad_lbn] != adp->ad_newblkno)
                          panic("%s: direct pointer #%jd mismatch %jd != %jd",
                              "softdep_write_inodeblock",
                              (intmax_t)adp->ad_lbn,
                              (intmax_t)dp->di_extb[adp->ad_lbn],
                              (intmax_t)adp->ad_newblkno);
                  deplist |= 1 << adp->ad_lbn;
                  if ((adp->ad_state & ATTACHED) == 0)
                          panic("softdep_write_inodeblock: Unknown state 0x%x",
                              adp->ad_state);
  #endif /* INVARIANTS */
                  adp->ad_state &= ~ATTACHED;
                  adp->ad_state |= UNDONE;
          }
          /*
           * The on-disk inode cannot claim to be any larger than the last
           * fragment that has been written. Otherwise, the on-disk inode
           * might have fragments that were not the last block in the ext
           * data which would corrupt the filesystem.
           */
          for (lastadp = NULL, adp = TAILQ_FIRST(&inodedep->id_extupdt); adp;
               lastadp = adp, adp = TAILQ_NEXT(adp, ad_next)) {
                  dp->di_extb[adp->ad_lbn] = adp->ad_oldblkno;
                  /* keep going until hitting a rollback to a frag */
                  if (adp->ad_oldsize == 0 || adp->ad_oldsize == fs->fs_bsize)
                          continue;
                  dp->di_extsize = fs->fs_bsize * adp->ad_lbn + adp->ad_oldsize;
                  for (i = adp->ad_lbn + 1; i < NXADDR; i++) {
  #ifdef INVARIANTS
                          if (dp->di_extb[i] != 0 && (deplist & (1 << i)) == 0)
                                  panic("softdep_write_inodeblock: lost dep1");
  #endif /* INVARIANTS */
                          dp->di_extb[i] = 0;
                  }
                  lastadp = NULL;
                  break;
          }
          /*
           * If we have zero'ed out the last allocated block of the ext
           * data, roll back the size to the last currently allocated block.
           * We know that this last allocated block is a full-sized as
           * we already checked for fragments in the loop above.
           */
          if (lastadp != NULL &&
              dp->di_extsize <= (lastadp->ad_lbn + 1) * fs->fs_bsize) {
                  for (i = lastadp->ad_lbn; i >= 0; i--)
                          if (dp->di_extb[i] != 0)
                                  break;
                  dp->di_extsize = (i + 1) * fs->fs_bsize;
          }
          /*
           * Set the file data dependencies to busy.
           */
          for (deplist = 0, adp = TAILQ_FIRST(&inodedep->id_inoupdt); adp;
               adp = TAILQ_NEXT(adp, ad_next)) {
  #ifdef INVARIANTS
                  if (deplist != 0 && prevlbn >= adp->ad_lbn)
                          panic("softdep_write_inodeblock: lbn order");
                  prevlbn = adp->ad_lbn;
                  if (adp->ad_lbn < NDADDR &&
                      dp->di_db[adp->ad_lbn] != adp->ad_newblkno)
                          panic("%s: direct pointer #%jd mismatch %jd != %jd",
                              "softdep_write_inodeblock",
                              (intmax_t)adp->ad_lbn,
                              (intmax_t)dp->di_db[adp->ad_lbn],
                              (intmax_t)adp->ad_newblkno);
                  if (adp->ad_lbn >= NDADDR &&
                      dp->di_ib[adp->ad_lbn - NDADDR] != adp->ad_newblkno)
                          panic("%s indirect pointer #%jd mismatch %jd != %jd",
                              "softdep_write_inodeblock:",
                              (intmax_t)adp->ad_lbn - NDADDR,
                              (intmax_t)dp->di_ib[adp->ad_lbn - NDADDR],
                              (intmax_t)adp->ad_newblkno);
                  deplist |= 1 << adp->ad_lbn;
                  if ((adp->ad_state & ATTACHED) == 0)
                          panic("softdep_write_inodeblock: Unknown state 0x%x",
                              adp->ad_state);
  #endif /* INVARIANTS */
                  adp->ad_state &= ~ATTACHED;
                  adp->ad_state |= UNDONE;
          }
          /*
           * The on-disk inode cannot claim to be any larger than the last
           * fragment that has been written. Otherwise, the on-disk inode
           * might have fragments that were not the last block in the file
           * which would corrupt the filesystem.
           */
          for (lastadp = NULL, adp = TAILQ_FIRST(&inodedep->id_inoupdt); adp;
               lastadp = adp, adp = TAILQ_NEXT(adp, ad_next)) {
                  if (adp->ad_lbn >= NDADDR)
                          break;
                  dp->di_db[adp->ad_lbn] = adp->ad_oldblkno;
                  /* keep going until hitting a rollback to a frag */
                  if (adp->ad_oldsize == 0 || adp->ad_oldsize == fs->fs_bsize)
                          continue;
                  dp->di_size = fs->fs_bsize * adp->ad_lbn + adp->ad_oldsize;
                  for (i = adp->ad_lbn + 1; i < NDADDR; i++) {
  #ifdef INVARIANTS
                          if (dp->di_db[i] != 0 && (deplist & (1 << i)) == 0)
                                  panic("softdep_write_inodeblock: lost dep2");
  #endif /* INVARIANTS */
                          dp->di_db[i] = 0;
                  }
                  for (i = 0; i < NIADDR; i++) {
  #ifdef INVARIANTS
                          if (dp->di_ib[i] != 0 &&
                              (deplist & ((1 << NDADDR) << i)) == 0)
                                  panic("softdep_write_inodeblock: lost dep3");
  #endif /* INVARIANTS */
                          dp->di_ib[i] = 0;
                  }
                  return;
          }
          /*
           * If we have zero'ed out the last allocated block of the file,
           * roll back the size to the last currently allocated block.
           * We know that this last allocated block is a full-sized as
           * we already checked for fragments in the loop above.
           */
          if (lastadp != NULL &&
              dp->di_size <= (lastadp->ad_lbn + 1) * fs->fs_bsize) {
                  for (i = lastadp->ad_lbn; i >= 0; i--)
                          if (dp->di_db[i] != 0)
                                  break;
                  dp->di_size = (i + 1) * fs->fs_bsize;
          }
          /*
           * The only dependencies are for indirect blocks.
           *
           * The file size for indirect block additions is not guaranteed.
           * Such a guarantee would be non-trivial to achieve. The conventional
           * synchronous write implementation also does not make this guarantee.
           * Fsck should catch and fix discrepancies. Arguably, the file size
           * can be over-estimated without destroying integrity when the file
           * moves into the indirect blocks (i.e., is large). If we want to
           * postpone fsck, we are stuck with this argument.
           */
          for (; adp; adp = TAILQ_NEXT(adp, ad_next))
                  dp->di_ib[adp->ad_lbn - NDADDR] = 0;
  }
  
  /*
   * This routine is called during the completion interrupt
   * service routine for a disk write (from the procedure called
   * by the device driver to inform the filesystem caches of
   * a request completion).  It should be called early in this
   * procedure, before the block is made available to other
   * processes or other routines are called.
   */
  static void 
  softdep_disk_write_complete(bp)
          struct buf *bp;         /* describes the completed disk write */
  {
          struct worklist *wk;
          struct worklist *owk;
          struct workhead reattach;
          struct newblk *newblk;
          struct allocindir *aip;
          struct allocdirect *adp;
          struct indirdep *indirdep;
          struct inodedep *inodedep;
          struct bmsafemap *bmsafemap;
  
          /*
           * If an error occurred while doing the write, then the data
           * has not hit the disk and the dependencies cannot be unrolled.
           */
          if ((bp->b_ioflags & BIO_ERROR) != 0 && (bp->b_flags & B_INVAL) == 0)
                  return;
          LIST_INIT(&reattach);
          /*
           * This lock must not be released anywhere in this code segment.
           */
          ACQUIRE_LOCK(&lk);
          owk = NULL;
          while ((wk = LIST_FIRST(&bp->b_dep)) != NULL) {
                  WORKLIST_REMOVE(wk);
                  if (wk == owk)
                          panic("duplicate worklist: %p\n", wk);
                  owk = wk;
                  switch (wk->wk_type) {
  
                  case D_PAGEDEP:
                          if (handle_written_filepage(WK_PAGEDEP(wk), bp))
                                  WORKLIST_INSERT(&reattach, wk);
                          continue;
  
                  case D_INODEDEP:
                          if (handle_written_inodeblock(WK_INODEDEP(wk), bp))
                                  WORKLIST_INSERT(&reattach, wk);
                          continue;
  
                  case D_BMSAFEMAP:
                          bmsafemap = WK_BMSAFEMAP(wk);
                          while ((newblk = LIST_FIRST(&bmsafemap->sm_newblkhd))) {
                                  newblk->nb_state |= DEPCOMPLETE;
                                  newblk->nb_bmsafemap = NULL;
                                  LIST_REMOVE(newblk, nb_deps);
                          }
                          while ((adp =
                             LIST_FIRST(&bmsafemap->sm_allocdirecthd))) {
                                  adp->ad_state |= DEPCOMPLETE;
                                  adp->ad_buf = NULL;
                                  LIST_REMOVE(adp, ad_deps);
                                  handle_allocdirect_partdone(adp);
                          }
                          while ((aip =
                              LIST_FIRST(&bmsafemap->sm_allocindirhd))) {
                                  aip->ai_state |= DEPCOMPLETE;
                                  aip->ai_buf = NULL;
                                  LIST_REMOVE(aip, ai_deps);
                                  handle_allocindir_partdone(aip);
                          }
                          while ((inodedep =
                               LIST_FIRST(&bmsafemap->sm_inodedephd)) != NULL) {
                                  inodedep->id_state |= DEPCOMPLETE;
                                  LIST_REMOVE(inodedep, id_deps);
                                  inodedep->id_buf = NULL;
                          }
                          WORKITEM_FREE(bmsafemap, D_BMSAFEMAP);
                          continue;
  
                  case D_MKDIR:
                          handle_written_mkdir(WK_MKDIR(wk), MKDIR_BODY);
                          continue;
  
                  case D_ALLOCDIRECT:
                          adp = WK_ALLOCDIRECT(wk);
                          adp->ad_state |= COMPLETE;
                          handle_allocdirect_partdone(adp);
                          continue;
  
                  case D_ALLOCINDIR:
                          aip = WK_ALLOCINDIR(wk);
                          aip->ai_state |= COMPLETE;
                          handle_allocindir_partdone(aip);
                          continue;
  
                  case D_INDIRDEP:
                          indirdep = WK_INDIRDEP(wk);
                          if (indirdep->ir_state & GOINGAWAY)
                                  panic("disk_write_complete: indirdep gone");
                          bcopy(indirdep->ir_saveddata, bp->b_data, bp->b_bcount);
                          FREE(indirdep->ir_saveddata, M_INDIRDEP);
                          indirdep->ir_saveddata = 0;
                          indirdep->ir_state &= ~UNDONE;
                          indirdep->ir_state |= ATTACHED;
                          while ((aip = LIST_FIRST(&indirdep->ir_donehd)) != 0) {
                                  handle_allocindir_partdone(aip);
                                  if (aip == LIST_FIRST(&indirdep->ir_donehd))
                                          panic("disk_write_complete: not gone");
                          }
                          WORKLIST_INSERT(&reattach, wk);
                          if ((bp->b_flags & B_DELWRI) == 0)
                                  stat_indir_blk_ptrs++;
                          bdirty(bp);
                          continue;
  
                  default:
                          panic("handle_disk_write_complete: Unknown type %s",
                              TYPENAME(wk->wk_type));
                          /* NOTREACHED */
                  }
          }
          /*
           * Reattach any requests that must be redone.
           */
          while ((wk = LIST_FIRST(&reattach)) != NULL) {
                  WORKLIST_REMOVE(wk);
                  WORKLIST_INSERT(&bp->b_dep, wk);
          }
          FREE_LOCK(&lk);
  }
  
  /*
   * Called from within softdep_disk_write_complete above. Note that
   * this routine is always called from interrupt level with further
   * splbio interrupts blocked.
   */
  static void 
  handle_allocdirect_partdone(adp)
          struct allocdirect *adp;        /* the completed allocdirect */
  {
          struct allocdirectlst *listhead;
          struct allocdirect *listadp;
          struct inodedep *inodedep;
          long bsize, delay;
  
          if ((adp->ad_state & ALLCOMPLETE) != ALLCOMPLETE)
                  return;
          if (adp->ad_buf != NULL)
                  panic("handle_allocdirect_partdone: dangling dep");
          /*
           * The on-disk inode cannot claim to be any larger than the last
           * fragment that has been written. Otherwise, the on-disk inode
           * might have fragments that were not the last block in the file
           * which would corrupt the filesystem. Thus, we cannot free any
           * allocdirects after one whose ad_oldblkno claims a fragment as
           * these blocks must be rolled back to zero before writing the inode.
           * We check the currently active set of allocdirects in id_inoupdt
           * or id_extupdt as appropriate.
           */
          inodedep = adp->ad_inodedep;
          bsize = inodedep->id_fs->fs_bsize;
          if (adp->ad_state & EXTDATA)
                  listhead = &inodedep->id_extupdt;
          else
                  listhead = &inodedep->id_inoupdt;
          TAILQ_FOREACH(listadp, listhead, ad_next) {
                  /* found our block */
                  if (listadp == adp)
                          break;
                  /* continue if ad_oldlbn is not a fragment */
                  if (listadp->ad_oldsize == 0 ||
                      listadp->ad_oldsize == bsize)
                          continue;
                  /* hit a fragment */
                  return;
          }
          /*
           * If we have reached the end of the current list without
           * finding the just finished dependency, then it must be
           * on the future dependency list. Future dependencies cannot
           * be freed until they are moved to the current list.
           */
          if (listadp == NULL) {
  #ifdef DEBUG
                  if (adp->ad_state & EXTDATA)
                          listhead = &inodedep->id_newextupdt;
                  else
                          listhead = &inodedep->id_newinoupdt;
                  TAILQ_FOREACH(listadp, listhead, ad_next)
                          /* found our block */
                          if (listadp == adp)
                                  break;
                  if (listadp == NULL)
                          panic("handle_allocdirect_partdone: lost dep");
  #endif /* DEBUG */
                  return;
          }
          /*
           * If we have found the just finished dependency, then free
           * it along with anything that follows it that is complete.
           * If the inode still has a bitmap dependency, then it has
           * never been written to disk, hence the on-disk inode cannot
           * reference the old fragment so we can free it without delay.
           */
          delay = (inodedep->id_state & DEPCOMPLETE);
          for (; adp; adp = listadp) {
                  listadp = TAILQ_NEXT(adp, ad_next);
                  if ((adp->ad_state & ALLCOMPLETE) != ALLCOMPLETE)
                          return;
                  free_allocdirect(listhead, adp, delay);
          }
  }
  
  /*
   * Called from within softdep_disk_write_complete above. Note that
   * this routine is always called from interrupt level with further
   * splbio interrupts blocked.
   */
  static void
  handle_allocindir_partdone(aip)
          struct allocindir *aip;         /* the completed allocindir */
  {
          struct indirdep *indirdep;
  
          if ((aip->ai_state & ALLCOMPLETE) != ALLCOMPLETE)
                  return;
          if (aip->ai_buf != NULL)
                  panic("handle_allocindir_partdone: dangling dependency");
          indirdep = aip->ai_indirdep;
          if (indirdep->ir_state & UNDONE) {
                  LIST_REMOVE(aip, ai_next);
                  LIST_INSERT_HEAD(&indirdep->ir_donehd, aip, ai_next);
                  return;
          }
          if (indirdep->ir_state & UFS1FMT)
                  ((ufs1_daddr_t *)indirdep->ir_savebp->b_data)[aip->ai_offset] =
                      aip->ai_newblkno;
          else
                  ((ufs2_daddr_t *)indirdep->ir_savebp->b_data)[aip->ai_offset] =
                      aip->ai_newblkno;
          LIST_REMOVE(aip, ai_next);
          if (aip->ai_freefrag != NULL)
                  add_to_worklist(&aip->ai_freefrag->ff_list);
          WORKITEM_FREE(aip, D_ALLOCINDIR);
  }
  
  /*
   * Called from within softdep_disk_write_complete above to restore
   * in-memory inode block contents to their most up-to-date state. Note
   * that this routine is always called from interrupt level with further
   * splbio interrupts blocked.
   */
  static int 
  handle_written_inodeblock(inodedep, bp)
          struct inodedep *inodedep;
          struct buf *bp;         /* buffer containing the inode block */
  {
          struct worklist *wk, *filefree;
          struct allocdirect *adp, *nextadp;
          struct ufs1_dinode *dp1 = NULL;
          struct ufs2_dinode *dp2 = NULL;
          int hadchanges, fstype;
  
          if ((inodedep->id_state & IOSTARTED) == 0)
                  panic("handle_written_inodeblock: not started");
          inodedep->id_state &= ~IOSTARTED;
          if (inodedep->id_fs->fs_magic == FS_UFS1_MAGIC) {
                  fstype = UFS1;
                  dp1 = (struct ufs1_dinode *)bp->b_data +
                      ino_to_fsbo(inodedep->id_fs, inodedep->id_ino);
          } else {
                  fstype = UFS2;
                  dp2 = (struct ufs2_dinode *)bp->b_data +
                      ino_to_fsbo(inodedep->id_fs, inodedep->id_ino);
          }
          /*
           * If we had to rollback the inode allocation because of
           * bitmaps being incomplete, then simply restore it.
           * Keep the block dirty so that it will not be reclaimed until
           * all associated dependencies have been cleared and the
           * corresponding updates written to disk.
           */
          if (inodedep->id_savedino1 != NULL) {
                  if (fstype == UFS1)
                          *dp1 = *inodedep->id_savedino1;
                  else
                          *dp2 = *inodedep->id_savedino2;
                  FREE(inodedep->id_savedino1, M_SAVEDINO);
                  inodedep->id_savedino1 = NULL;
                  if ((bp->b_flags & B_DELWRI) == 0)
                          stat_inode_bitmap++;
                  bdirty(bp);
                  return (1);
          }
          inodedep->id_state |= COMPLETE;
          /*
           * Roll forward anything that had to be rolled back before 
           * the inode could be updated.
           */
          hadchanges = 0;
          for (adp = TAILQ_FIRST(&inodedep->id_inoupdt); adp; adp = nextadp) {
                  nextadp = TAILQ_NEXT(adp, ad_next);
                  if (adp->ad_state & ATTACHED)
                          panic("handle_written_inodeblock: new entry");
                  if (fstype == UFS1) {
                          if (adp->ad_lbn < NDADDR) {
                                  if (dp1->di_db[adp->ad_lbn]!=adp->ad_oldblkno)
                                          panic("%s %s #%jd mismatch %d != %jd",
                                              "handle_written_inodeblock:",
                                              "direct pointer",
                                              (intmax_t)adp->ad_lbn,
                                              dp1->di_db[adp->ad_lbn],
                                              (intmax_t)adp->ad_oldblkno);
                                  dp1->di_db[adp->ad_lbn] = adp->ad_newblkno;
                          } else {
                                  if (dp1->di_ib[adp->ad_lbn - NDADDR] != 0)
                                          panic("%s: %s #%jd allocated as %d",
                                              "handle_written_inodeblock",
                                              "indirect pointer",
                                              (intmax_t)adp->ad_lbn - NDADDR,
                                              dp1->di_ib[adp->ad_lbn - NDADDR]);
                                  dp1->di_ib[adp->ad_lbn - NDADDR] =
                                      adp->ad_newblkno;
                          }
                  } else {
                          if (adp->ad_lbn < NDADDR) {
                                  if (dp2->di_db[adp->ad_lbn]!=adp->ad_oldblkno)
                                          panic("%s: %s #%jd %s %jd != %jd",
                                              "handle_written_inodeblock",
                                              "direct pointer",
                                              (intmax_t)adp->ad_lbn, "mismatch",
                                              (intmax_t)dp2->di_db[adp->ad_lbn],
                                              (intmax_t)adp->ad_oldblkno);
                                  dp2->di_db[adp->ad_lbn] = adp->ad_newblkno;
                          } else {
                                  if (dp2->di_ib[adp->ad_lbn - NDADDR] != 0)
                                          panic("%s: %s #%jd allocated as %jd",
                                              "handle_written_inodeblock",
                                              "indirect pointer",
                                              (intmax_t)adp->ad_lbn - NDADDR,
                                              (intmax_t)
                                              dp2->di_ib[adp->ad_lbn - NDADDR]);
                                  dp2->di_ib[adp->ad_lbn - NDADDR] =
                                      adp->ad_newblkno;
                          }
                  }
                  adp->ad_state &= ~UNDONE;
                  adp->ad_state |= ATTACHED;
                  hadchanges = 1;
          }
          for (adp = TAILQ_FIRST(&inodedep->id_extupdt); adp; adp = nextadp) {
                  nextadp = TAILQ_NEXT(adp, ad_next);
                  if (adp->ad_state & ATTACHED)
                          panic("handle_written_inodeblock: new entry");
                  if (dp2->di_extb[adp->ad_lbn] != adp->ad_oldblkno)
                          panic("%s: direct pointers #%jd %s %jd != %jd",
                              "handle_written_inodeblock",
                              (intmax_t)adp->ad_lbn, "mismatch",
                              (intmax_t)dp2->di_extb[adp->ad_lbn],
                              (intmax_t)adp->ad_oldblkno);
                  dp2->di_extb[adp->ad_lbn] = adp->ad_newblkno;
                  adp->ad_state &= ~UNDONE;
                  adp->ad_state |= ATTACHED;
                  hadchanges = 1;
          }
          if (hadchanges && (bp->b_flags & B_DELWRI) == 0)
                  stat_direct_blk_ptrs++;
          /*
           * Reset the file size to its most up-to-date value.
           */
          if (inodedep->id_savedsize == -1 || inodedep->id_savedextsize == -1)
                  panic("handle_written_inodeblock: bad size");
          if (fstype == UFS1) {
                  if (dp1->di_size != inodedep->id_savedsize) {
                          dp1->di_size = inodedep->id_savedsize;
                          hadchanges = 1;
                  }
          } else {
                  if (dp2->di_size != inodedep->id_savedsize) {
                          dp2->di_size = inodedep->id_savedsize;
                          hadchanges = 1;
                  }
                  if (dp2->di_extsize != inodedep->id_savedextsize) {
                          dp2->di_extsize = inodedep->id_savedextsize;
                          hadchanges = 1;
                  }
          }
          inodedep->id_savedsize = -1;
          inodedep->id_savedextsize = -1;
          /*
           * If there were any rollbacks in the inode block, then it must be
           * marked dirty so that its will eventually get written back in
           * its correct form.
           */
          if (hadchanges)
                  bdirty(bp);
          /*
           * Process any allocdirects that completed during the update.
           */
          if ((adp = TAILQ_FIRST(&inodedep->id_inoupdt)) != NULL)
                  handle_allocdirect_partdone(adp);
          if ((adp = TAILQ_FIRST(&inodedep->id_extupdt)) != NULL)
                  handle_allocdirect_partdone(adp);
          /*
           * Process deallocations that were held pending until the
           * inode had been written to disk. Freeing of the inode
           * is delayed until after all blocks have been freed to
           * avoid creation of new <vfsid, inum, lbn> triples
           * before the old ones have been deleted.
           */
          filefree = NULL;
          while ((wk = LIST_FIRST(&inodedep->id_bufwait)) != NULL) {
                  WORKLIST_REMOVE(wk);
                  switch (wk->wk_type) {
  
                  case D_FREEFILE:
                          /*
                           * We defer adding filefree to the worklist until
                           * all other additions have been made to ensure
                           * that it will be done after all the old blocks
                           * have been freed.
                           */
                          if (filefree != NULL)
                                  panic("handle_written_inodeblock: filefree");
                          filefree = wk;
                          continue;
  
                  case D_MKDIR:
                          handle_written_mkdir(WK_MKDIR(wk), MKDIR_PARENT);
                          continue;
  
                  case D_DIRADD:
                          diradd_inode_written(WK_DIRADD(wk), inodedep);
                          continue;
  
                  case D_FREEBLKS:
                          wk->wk_state |= COMPLETE;
                          if ((wk->wk_state  & ALLCOMPLETE) != ALLCOMPLETE)
                                  continue;
                           /* -- fall through -- */
                  case D_FREEFRAG:
                  case D_DIRREM:
                          add_to_worklist(wk);
                          continue;
  
                  case D_NEWDIRBLK:
                          free_newdirblk(WK_NEWDIRBLK(wk));
                          continue;
  
                  default:
                          panic("handle_written_inodeblock: Unknown type %s",
                              TYPENAME(wk->wk_type));
                          /* NOTREACHED */
                  }
          }
          if (filefree != NULL) {
                  if (free_inodedep(inodedep) == 0)
                          panic("handle_written_inodeblock: live inodedep");
                  add_to_worklist(filefree);
                  return (0);
          }
  
          /*
           * If no outstanding dependencies, free it.
           */
          if (free_inodedep(inodedep) ||
              (TAILQ_FIRST(&inodedep->id_inoupdt) == 0 &&
               TAILQ_FIRST(&inodedep->id_extupdt) == 0))
                  return (0);
          return (hadchanges);
  }
  
  /*
   * Process a diradd entry after its dependent inode has been written.
   * This routine must be called with splbio interrupts blocked.
   */
  static void
  diradd_inode_written(dap, inodedep)
          struct diradd *dap;
          struct inodedep *inodedep;
  {
          struct pagedep *pagedep;
  
          dap->da_state |= COMPLETE;
          if ((dap->da_state & ALLCOMPLETE) == ALLCOMPLETE) {
                  if (dap->da_state & DIRCHG)
                          pagedep = dap->da_previous->dm_pagedep;
                  else
                          pagedep = dap->da_pagedep;
                  LIST_REMOVE(dap, da_pdlist);
                  LIST_INSERT_HEAD(&pagedep->pd_pendinghd, dap, da_pdlist);
          }
          WORKLIST_INSERT(&inodedep->id_pendinghd, &dap->da_list);
  }
  
  /*
   * Handle the completion of a mkdir dependency.
   */
  static void
  handle_written_mkdir(mkdir, type)
          struct mkdir *mkdir;
          int type;
  {
          struct diradd *dap;
          struct pagedep *pagedep;
  
          if (mkdir->md_state != type)
                  panic("handle_written_mkdir: bad type");
          dap = mkdir->md_diradd;
          dap->da_state &= ~type;
          if ((dap->da_state & (MKDIR_PARENT | MKDIR_BODY)) == 0)
                  dap->da_state |= DEPCOMPLETE;
          if ((dap->da_state & ALLCOMPLETE) == ALLCOMPLETE) {
                  if (dap->da_state & DIRCHG)
                          pagedep = dap->da_previous->dm_pagedep;
                  else
                          pagedep = dap->da_pagedep;
                  LIST_REMOVE(dap, da_pdlist);
                  LIST_INSERT_HEAD(&pagedep->pd_pendinghd, dap, da_pdlist);
          }
          LIST_REMOVE(mkdir, md_mkdirs);
          WORKITEM_FREE(mkdir, D_MKDIR);
  }
  
  /*
   * Called from within softdep_disk_write_complete above.
   * A write operation was just completed. Removed inodes can
   * now be freed and associated block pointers may be committed.
   * Note that this routine is always called from interrupt level
   * with further splbio interrupts blocked.
   */
  static int 
  handle_written_filepage(pagedep, bp)
          struct pagedep *pagedep;
          struct buf *bp;         /* buffer containing the written page */
  {
          struct dirrem *dirrem;
          struct diradd *dap, *nextdap;
          struct direct *ep;
          int i, chgs;
  
          if ((pagedep->pd_state & IOSTARTED) == 0)
                  panic("handle_written_filepage: not started");
          pagedep->pd_state &= ~IOSTARTED;
          /*
           * Process any directory removals that have been committed.
           */
          while ((dirrem = LIST_FIRST(&pagedep->pd_dirremhd)) != NULL) {
                  LIST_REMOVE(dirrem, dm_next);
                  dirrem->dm_dirinum = pagedep->pd_ino;
                  add_to_worklist(&dirrem->dm_list);
          }
          /*
           * Free any directory additions that have been committed.
           * If it is a newly allocated block, we have to wait until
           * the on-disk directory inode claims the new block.
           */
          if ((pagedep->pd_state & NEWBLOCK) == 0)
                  while ((dap = LIST_FIRST(&pagedep->pd_pendinghd)) != NULL)
                          free_diradd(dap);
          /*
           * Uncommitted directory entries must be restored.
           */
          for (chgs = 0, i = 0; i < DAHASHSZ; i++) {
                  for (dap = LIST_FIRST(&pagedep->pd_diraddhd[i]); dap;
                       dap = nextdap) {
                          nextdap = LIST_NEXT(dap, da_pdlist);
                          if (dap->da_state & ATTACHED)
                                  panic("handle_written_filepage: attached");
                          ep = (struct direct *)
                              ((char *)bp->b_data + dap->da_offset);
                          ep->d_ino = dap->da_newinum;
                          dap->da_state &= ~UNDONE;
                          dap->da_state |= ATTACHED;
                          chgs = 1;
                          /*
                           * If the inode referenced by the directory has
                           * been written out, then the dependency can be
                           * moved to the pending list.
                           */
                          if ((dap->da_state & ALLCOMPLETE) == ALLCOMPLETE) {
                                  LIST_REMOVE(dap, da_pdlist);
                                  LIST_INSERT_HEAD(&pagedep->pd_pendinghd, dap,
                                      da_pdlist);
                          }
                  }
          }
          /*
           * If there were any rollbacks in the directory, then it must be
           * marked dirty so that its will eventually get written back in
           * its correct form.
           */
          if (chgs) {
                  if ((bp->b_flags & B_DELWRI) == 0)
                          stat_dir_entry++;
                  bdirty(bp);
                  return (1);
          }
          /*
           * If we are not waiting for a new directory block to be
           * claimed by its inode, then the pagedep will be freed.
           * Otherwise it will remain to track any new entries on
           * the page in case they are fsync'ed.
           */
          if ((pagedep->pd_state & NEWBLOCK) == 0) {
                  LIST_REMOVE(pagedep, pd_hash);
                  WORKITEM_FREE(pagedep, D_PAGEDEP);
          }
          return (0);
  }
  
  /*
   * Writing back in-core inode structures.
   * 
   * The filesystem only accesses an inode's contents when it occupies an
   * "in-core" inode structure.  These "in-core" structures are separate from
   * the page frames used to cache inode blocks.  Only the latter are
   * transferred to/from the disk.  So, when the updated contents of the
   * "in-core" inode structure are copied to the corresponding in-memory inode
   * block, the dependencies are also transferred.  The following procedure is
   * called when copying a dirty "in-core" inode to a cached inode block.
   */
  
  /*
   * Called when an inode is loaded from disk. If the effective link count
   * differed from the actual link count when it was last flushed, then we
   * need to ensure that the correct effective link count is put back.
   */
  void 
  softdep_load_inodeblock(ip)
          struct inode *ip;       /* the "in_core" copy of the inode */
  {
          struct inodedep *inodedep;
  
          /*
           * Check for alternate nlink count.
           */
          ip->i_effnlink = ip->i_nlink;
          ACQUIRE_LOCK(&lk);
          if (inodedep_lookup(UFSTOVFS(ip->i_ump),
              ip->i_number, 0, &inodedep) == 0) {
                  FREE_LOCK(&lk);
                  return;
          }
          ip->i_effnlink -= inodedep->id_nlinkdelta;
          if (inodedep->id_state & SPACECOUNTED)
                  ip->i_flag |= IN_SPACECOUNTED;
          FREE_LOCK(&lk);
  }
  
  /*
   * This routine is called just before the "in-core" inode
   * information is to be copied to the in-memory inode block.
   * Recall that an inode block contains several inodes. If
   * the force flag is set, then the dependencies will be
   * cleared so that the update can always be made. Note that
   * the buffer is locked when this routine is called, so we
   * will never be in the middle of writing the inode block 
   * to disk.
   */
  void 
  softdep_update_inodeblock(ip, bp, waitfor)
          struct inode *ip;       /* the "in_core" copy of the inode */
          struct buf *bp;         /* the buffer containing the inode block */
          int waitfor;            /* nonzero => update must be allowed */
  {
          struct inodedep *inodedep;
          struct worklist *wk;
          struct mount *mp;
          struct buf *ibp;
          int error;
  
          /*
           * If the effective link count is not equal to the actual link
           * count, then we must track the difference in an inodedep while
           * the inode is (potentially) tossed out of the cache. Otherwise,
           * if there is no existing inodedep, then there are no dependencies
           * to track.
           */
          mp = UFSTOVFS(ip->i_ump);
          ACQUIRE_LOCK(&lk);
          if (inodedep_lookup(mp, ip->i_number, 0, &inodedep) == 0) {
                  FREE_LOCK(&lk);
                  if (ip->i_effnlink != ip->i_nlink)
                          panic("softdep_update_inodeblock: bad link count");
                  return;
          }
          if (inodedep->id_nlinkdelta != ip->i_nlink - ip->i_effnlink)
                  panic("softdep_update_inodeblock: bad delta");
          /*
           * Changes have been initiated. Anything depending on these
           * changes cannot occur until this inode has been written.
           */
          inodedep->id_state &= ~COMPLETE;
          if ((inodedep->id_state & ONWORKLIST) == 0)
                  WORKLIST_INSERT(&bp->b_dep, &inodedep->id_list);
          /*
           * Any new dependencies associated with the incore inode must 
           * now be moved to the list associated with the buffer holding
           * the in-memory copy of the inode. Once merged process any
           * allocdirects that are completed by the merger.
           */
          merge_inode_lists(&inodedep->id_newinoupdt, &inodedep->id_inoupdt);
          if (!TAILQ_EMPTY(&inodedep->id_inoupdt))
                  handle_allocdirect_partdone(TAILQ_FIRST(&inodedep->id_inoupdt));
          merge_inode_lists(&inodedep->id_newextupdt, &inodedep->id_extupdt);
          if (!TAILQ_EMPTY(&inodedep->id_extupdt))
                  handle_allocdirect_partdone(TAILQ_FIRST(&inodedep->id_extupdt));
          /*
           * Now that the inode has been pushed into the buffer, the
           * operations dependent on the inode being written to disk
           * can be moved to the id_bufwait so that they will be
           * processed when the buffer I/O completes.
           */
          while ((wk = LIST_FIRST(&inodedep->id_inowait)) != NULL) {
                  WORKLIST_REMOVE(wk);
                  WORKLIST_INSERT(&inodedep->id_bufwait, wk);
          }
          /*
           * Newly allocated inodes cannot be written until the bitmap
           * that allocates them have been written (indicated by
           * DEPCOMPLETE being set in id_state). If we are doing a
           * forced sync (e.g., an fsync on a file), we force the bitmap
           * to be written so that the update can be done.
           */
          if (waitfor == 0) {
                  FREE_LOCK(&lk);
                  return;
          }
  retry:
          if ((inodedep->id_state & DEPCOMPLETE) != 0) {
                  FREE_LOCK(&lk);
                  return;
          }
          ibp = inodedep->id_buf;
          ibp = getdirtybuf(ibp, &lk, MNT_WAIT);
          if (ibp == NULL) {
                  /*
                   * If ibp came back as NULL, the dependency could have been
                   * freed while we slept.  Look it up again, and check to see
                   * that it has completed.
                   */
                  if (inodedep_lookup(mp, ip->i_number, 0, &inodedep) != 0)
                          goto retry;
                  FREE_LOCK(&lk);
                  return;
          }
          FREE_LOCK(&lk);
          if ((error = bwrite(ibp)) != 0)
                  softdep_error("softdep_update_inodeblock: bwrite", error);
  }
  
  /*
   * Merge the a new inode dependency list (such as id_newinoupdt) into an
   * old inode dependency list (such as id_inoupdt). This routine must be
   * called with splbio interrupts blocked.
   */
  static void
  merge_inode_lists(newlisthead, oldlisthead)
          struct allocdirectlst *newlisthead;
          struct allocdirectlst *oldlisthead;
  {
          struct allocdirect *listadp, *newadp;
  
          newadp = TAILQ_FIRST(newlisthead);
          for (listadp = TAILQ_FIRST(oldlisthead); listadp && newadp;) {
                  if (listadp->ad_lbn < newadp->ad_lbn) {
                          listadp = TAILQ_NEXT(listadp, ad_next);
                          continue;
                  }
                  TAILQ_REMOVE(newlisthead, newadp, ad_next);
                  TAILQ_INSERT_BEFORE(listadp, newadp, ad_next);
                  if (listadp->ad_lbn == newadp->ad_lbn) {
                          allocdirect_merge(oldlisthead, newadp,
                              listadp);
                          listadp = newadp;
                  }
                  newadp = TAILQ_FIRST(newlisthead);
          }
          while ((newadp = TAILQ_FIRST(newlisthead)) != NULL) {
                  TAILQ_REMOVE(newlisthead, newadp, ad_next);
                  TAILQ_INSERT_TAIL(oldlisthead, newadp, ad_next);
          }
  }
  
  /*
   * If we are doing an fsync, then we must ensure that any directory
   * entries for the inode have been written after the inode gets to disk.
   */
  int
  softdep_fsync(vp)
          struct vnode *vp;       /* the "in_core" copy of the inode */
  {
          struct inodedep *inodedep;
          struct pagedep *pagedep;
          struct worklist *wk;
          struct diradd *dap;
          struct mount *mp;
          struct vnode *pvp;
          struct inode *ip;
          struct buf *bp;
          struct fs *fs;
          struct thread *td = curthread;
          int error, flushparent, pagedep_new_block;
          ino_t parentino;
          ufs_lbn_t lbn;
  
          ip = VTOI(vp);
          fs = ip->i_fs;
          mp = vp->v_mount;
          ACQUIRE_LOCK(&lk);
          if (inodedep_lookup(mp, ip->i_number, 0, &inodedep) == 0) {
                  FREE_LOCK(&lk);
                  return (0);
          }
          if (!LIST_EMPTY(&inodedep->id_inowait) ||
              !LIST_EMPTY(&inodedep->id_bufwait) ||
              !TAILQ_EMPTY(&inodedep->id_extupdt) ||
              !TAILQ_EMPTY(&inodedep->id_newextupdt) ||
              !TAILQ_EMPTY(&inodedep->id_inoupdt) ||
              !TAILQ_EMPTY(&inodedep->id_newinoupdt))
                  panic("softdep_fsync: pending ops");
          for (error = 0, flushparent = 0; ; ) {
                  if ((wk = LIST_FIRST(&inodedep->id_pendinghd)) == NULL)
                          break;
                  if (wk->wk_type != D_DIRADD)
                          panic("softdep_fsync: Unexpected type %s",
                              TYPENAME(wk->wk_type));
                  dap = WK_DIRADD(wk);
                  /*
                   * Flush our parent if this directory entry has a MKDIR_PARENT
                   * dependency or is contained in a newly allocated block.
                   */
                  if (dap->da_state & DIRCHG)
                          pagedep = dap->da_previous->dm_pagedep;
                  else
                          pagedep = dap->da_pagedep;
                  parentino = pagedep->pd_ino;
                  lbn = pagedep->pd_lbn;
                  if ((dap->da_state & (MKDIR_BODY | COMPLETE)) != COMPLETE)
                          panic("softdep_fsync: dirty");
                  if ((dap->da_state & MKDIR_PARENT) ||
                      (pagedep->pd_state & NEWBLOCK))
                          flushparent = 1;
                  else
                          flushparent = 0;
                  /*
                   * If we are being fsync'ed as part of vgone'ing this vnode,
                   * then we will not be able to release and recover the
                   * vnode below, so we just have to give up on writing its
                   * directory entry out. It will eventually be written, just
                   * not now, but then the user was not asking to have it
                   * written, so we are not breaking any promises.
                   */
                  if (vp->v_iflag & VI_DOOMED)
                          break;
                  /*
                   * We prevent deadlock by always fetching inodes from the
                   * root, moving down the directory tree. Thus, when fetching
                   * our parent directory, we first try to get the lock. If
                   * that fails, we must unlock ourselves before requesting
                   * the lock on our parent. See the comment in ufs_lookup
                   * for details on possible races.
                   */
                  FREE_LOCK(&lk);
                  if (ffs_vget(mp, parentino, LK_NOWAIT | LK_EXCLUSIVE, &pvp)) {
                          VOP_UNLOCK(vp, 0, td);
                          error = ffs_vget(mp, parentino, LK_EXCLUSIVE, &pvp);
                          vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
                          if (error != 0)
                                  return (error);
                  }
                  /*
                   * All MKDIR_PARENT dependencies and all the NEWBLOCK pagedeps
                   * that are contained in direct blocks will be resolved by 
                   * doing a ffs_update. Pagedeps contained in indirect blocks
                   * may require a complete sync'ing of the directory. So, we
                   * try the cheap and fast ffs_update first, and if that fails,
                   * then we do the slower ffs_syncvnode of the directory.
                   */
                  if (flushparent) {
                          int locked;
  
                          if ((error = ffs_update(pvp, 1)) != 0) {
                                  vput(pvp);
                                  return (error);
                          }
                          ACQUIRE_LOCK(&lk);
                          locked = 1;
                          if (inodedep_lookup(mp, ip->i_number, 0, &inodedep) != 0) {
                                  if ((wk = LIST_FIRST(&inodedep->id_pendinghd)) != NULL) {
                                          if (wk->wk_type != D_DIRADD)
                                                  panic("softdep_fsync: Unexpected type %s",
                                                        TYPENAME(wk->wk_type));
                                          dap = WK_DIRADD(wk);
                                          if (dap->da_state & DIRCHG)
                                                  pagedep = dap->da_previous->dm_pagedep;
                                          else
                                                  pagedep = dap->da_pagedep;
                                          pagedep_new_block = pagedep->pd_state & NEWBLOCK;
                                          FREE_LOCK(&lk);
                                          locked = 0;
                                          if (pagedep_new_block &&
                                              (error = ffs_syncvnode(pvp, MNT_WAIT))) {
                                                  vput(pvp);
                                                  return (error);
                                          }
                                  }
                          }
                          if (locked)
                                  FREE_LOCK(&lk);
                  }
                  /*
                   * Flush directory page containing the inode's name.
                   */
                  error = bread(pvp, lbn, blksize(fs, VTOI(pvp), lbn), td->td_ucred,
                      &bp);
                  if (error == 0)
                          error = bwrite(bp);
                  else
                          brelse(bp);
                  vput(pvp);
                  if (error != 0)
                          return (error);
                  ACQUIRE_LOCK(&lk);
                  if (inodedep_lookup(mp, ip->i_number, 0, &inodedep) == 0)
                          break;
          }
          FREE_LOCK(&lk);
          return (0);
  }
  
  /*
   * Flush all the dirty bitmaps associated with the block device
   * before flushing the rest of the dirty blocks so as to reduce
   * the number of dependencies that will have to be rolled back.
   */
  void
  softdep_fsync_mountdev(vp)
          struct vnode *vp;
  {
          struct buf *bp, *nbp;
          struct worklist *wk;
  
          if (!vn_isdisk(vp, NULL))
                  panic("softdep_fsync_mountdev: vnode not a disk");
  restart:
          ACQUIRE_LOCK(&lk);
          VI_LOCK(vp);
          TAILQ_FOREACH_SAFE(bp, &vp->v_bufobj.bo_dirty.bv_hd, b_bobufs, nbp) {
                  /* 
                   * If it is already scheduled, skip to the next buffer.
                   */
                  if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT, NULL))
                          continue;
  
                  if ((bp->b_flags & B_DELWRI) == 0)
                          panic("softdep_fsync_mountdev: not dirty");
                  /*
                   * We are only interested in bitmaps with outstanding
                   * dependencies.
                   */
                  if ((wk = LIST_FIRST(&bp->b_dep)) == NULL ||
                      wk->wk_type != D_BMSAFEMAP ||
                      (bp->b_vflags & BV_BKGRDINPROG)) {
                          BUF_UNLOCK(bp);
                          continue;
                  }
                  VI_UNLOCK(vp);
                  FREE_LOCK(&lk);
                  bremfree(bp);
                  (void) bawrite(bp);
                  goto restart;
          }
          FREE_LOCK(&lk);
          drain_output(vp);
          VI_UNLOCK(vp);
  }
  
  /*
   * This routine is called when we are trying to synchronously flush a
   * file. This routine must eliminate any filesystem metadata dependencies
   * so that the syncing routine can succeed by pushing the dirty blocks
   * associated with the file. If any I/O errors occur, they are returned.
   */
  int
  softdep_sync_metadata(struct vnode *vp)
  {
          struct pagedep *pagedep;
          struct allocdirect *adp;
          struct allocindir *aip;
          struct buf *bp, *nbp;
          struct worklist *wk;
          int i, error, waitfor;
  
          if (!DOINGSOFTDEP(vp))
                  return (0);
          /*
           * Ensure that any direct block dependencies have been cleared.
           */
          ACQUIRE_LOCK(&lk);
          if ((error = flush_inodedep_deps(vp->v_mount, VTOI(vp)->i_number))) {
                  FREE_LOCK(&lk);
                  return (error);
          }
          FREE_LOCK(&lk);
          /*
           * For most files, the only metadata dependencies are the
           * cylinder group maps that allocate their inode or blocks.
           * The block allocation dependencies can be found by traversing
           * the dependency lists for any buffers that remain on their
           * dirty buffer list. The inode allocation dependency will
           * be resolved when the inode is updated with MNT_WAIT.
           * This work is done in two passes. The first pass grabs most
           * of the buffers and begins asynchronously writing them. The
           * only way to wait for these asynchronous writes is to sleep
           * on the filesystem vnode which may stay busy for a long time
           * if the filesystem is active. So, instead, we make a second
           * pass over the dependencies blocking on each write. In the
           * usual case we will be blocking against a write that we
           * initiated, so when it is done the dependency will have been
           * resolved. Thus the second pass is expected to end quickly.
           */
          waitfor = MNT_NOWAIT;
  
  top:
          /*
           * We must wait for any I/O in progress to finish so that
           * all potential buffers on the dirty list will be visible.
           */
          VI_LOCK(vp);
          drain_output(vp);
          while ((bp = TAILQ_FIRST(&vp->v_bufobj.bo_dirty.bv_hd)) != NULL) {
                  bp = getdirtybuf(bp, VI_MTX(vp), MNT_WAIT);
                  if (bp)
                          break;
          }
          VI_UNLOCK(vp);
          if (bp == NULL)
                  return (0);
  loop:
          /* While syncing snapshots, we must allow recursive lookups */
          bp->b_lock.lk_flags |= LK_CANRECURSE;
          ACQUIRE_LOCK(&lk);
          /*
           * As we hold the buffer locked, none of its dependencies
           * will disappear.
           */
          LIST_FOREACH(wk, &bp->b_dep, wk_list) {
                  switch (wk->wk_type) {
  
                  case D_ALLOCDIRECT:
                          adp = WK_ALLOCDIRECT(wk);
                          if (adp->ad_state & DEPCOMPLETE)
                                  continue;
                          nbp = adp->ad_buf;
                          nbp = getdirtybuf(nbp, &lk, waitfor);
                          if (nbp == NULL)
                                  continue;
                          FREE_LOCK(&lk);
                          if (waitfor == MNT_NOWAIT) {
                                  bawrite(nbp);
                          } else if ((error = bwrite(nbp)) != 0) {
                                  break;
                          }
                          ACQUIRE_LOCK(&lk);
                          continue;
  
                  case D_ALLOCINDIR:
                          aip = WK_ALLOCINDIR(wk);
                          if (aip->ai_state & DEPCOMPLETE)
                                  continue;
                          nbp = aip->ai_buf;
                          nbp = getdirtybuf(nbp, &lk, waitfor);
                          if (nbp == NULL)
                                  continue;
                          FREE_LOCK(&lk);
                          if (waitfor == MNT_NOWAIT) {
                                  bawrite(nbp);
                          } else if ((error = bwrite(nbp)) != 0) {
                                  break;
                          }
                          ACQUIRE_LOCK(&lk);
                          continue;
  
                  case D_INDIRDEP:
                  restart:
  
                          LIST_FOREACH(aip, &WK_INDIRDEP(wk)->ir_deplisthd, ai_next) {
                                  if (aip->ai_state & DEPCOMPLETE)
                                          continue;
                                  nbp = aip->ai_buf;
                                  nbp = getdirtybuf(nbp, &lk, MNT_WAIT);
                                  if (nbp == NULL)
                                          goto restart;
                                  FREE_LOCK(&lk);
                                  if ((error = bwrite(nbp)) != 0) {
                                          goto loop_end;
                                  }
                                  ACQUIRE_LOCK(&lk);
                                  goto restart;
                          }
                          continue;
  
                  case D_INODEDEP:
                          if ((error = flush_inodedep_deps(wk->wk_mp,
                              WK_INODEDEP(wk)->id_ino)) != 0) {
                                  FREE_LOCK(&lk);
                                  break;
                          }
                          continue;
  
                  case D_PAGEDEP:
                          /*
                           * We are trying to sync a directory that may
                           * have dependencies on both its own metadata
                           * and/or dependencies on the inodes of any
                           * recently allocated files. We walk its diradd
                           * lists pushing out the associated inode.
                           */
                          pagedep = WK_PAGEDEP(wk);
                          for (i = 0; i < DAHASHSZ; i++) {
                                  if (LIST_FIRST(&pagedep->pd_diraddhd[i]) == 0)
                                          continue;
                                  if ((error =
                                      flush_pagedep_deps(vp, wk->wk_mp,
                                                  &pagedep->pd_diraddhd[i]))) {
                                          FREE_LOCK(&lk);
                                          goto loop_end;
                                  }
                          }
                          continue;
  
                  case D_MKDIR:
                          /*
                           * This case should never happen if the vnode has
                           * been properly sync'ed. However, if this function
                           * is used at a place where the vnode has not yet
                           * been sync'ed, this dependency can show up. So,
                           * rather than panic, just flush it.
                           */
                          nbp = WK_MKDIR(wk)->md_buf;
                          nbp = getdirtybuf(nbp, &lk, waitfor);
                          if (nbp == NULL)
                                  continue;
                          FREE_LOCK(&lk);
                          if (waitfor == MNT_NOWAIT) {
                                  bawrite(nbp);
                          } else if ((error = bwrite(nbp)) != 0) {
                                  break;
                          }
                          ACQUIRE_LOCK(&lk);
                          continue;
  
                  case D_BMSAFEMAP:
                          /*
                           * This case should never happen if the vnode has
                           * been properly sync'ed. However, if this function
                           * is used at a place where the vnode has not yet
                           * been sync'ed, this dependency can show up. So,
                           * rather than panic, just flush it.
                           */
                          nbp = WK_BMSAFEMAP(wk)->sm_buf;
                          nbp = getdirtybuf(nbp, &lk, waitfor);
                          if (nbp == NULL)
                                  continue;
                          FREE_LOCK(&lk);
                          if (waitfor == MNT_NOWAIT) {
                                  bawrite(nbp);
                          } else if ((error = bwrite(nbp)) != 0) {
                                  break;
                          }
                          ACQUIRE_LOCK(&lk);
                          continue;
  
                  default:
                          panic("softdep_sync_metadata: Unknown type %s",
                              TYPENAME(wk->wk_type));
                          /* NOTREACHED */
                  }
          loop_end:
                  /* We reach here only in error and unlocked */
                  if (error == 0)
                          panic("softdep_sync_metadata: zero error");
                  bp->b_lock.lk_flags &= ~LK_CANRECURSE;
                  bawrite(bp);
                  return (error);
          }
          FREE_LOCK(&lk);
          VI_LOCK(vp);
          while ((nbp = TAILQ_NEXT(bp, b_bobufs)) != NULL) {
                  nbp = getdirtybuf(nbp, VI_MTX(vp), MNT_WAIT);
                  if (nbp)
                          break;
          }
          VI_UNLOCK(vp);
          bp->b_lock.lk_flags &= ~LK_CANRECURSE;
          bawrite(bp);
          if (nbp != NULL) {
                  bp = nbp;
                  goto loop;
          }
          /*
           * The brief unlock is to allow any pent up dependency
           * processing to be done. Then proceed with the second pass.
           */
          if (waitfor == MNT_NOWAIT) {
                  waitfor = MNT_WAIT;
                  goto top;
          }
  
          /*
           * If we have managed to get rid of all the dirty buffers,
           * then we are done. For certain directories and block
           * devices, we may need to do further work.
           *
           * We must wait for any I/O in progress to finish so that
           * all potential buffers on the dirty list will be visible.
           */
          VI_LOCK(vp);
          drain_output(vp);
          VI_UNLOCK(vp);
          return (0);
  }
  
  /*
   * Flush the dependencies associated with an inodedep.
   * Called with splbio blocked.
   */
  static int
  flush_inodedep_deps(mp, ino)
          struct mount *mp;
          ino_t ino;
  {
          struct inodedep *inodedep;
          int error, waitfor;
  
          /*
           * This work is done in two passes. The first pass grabs most
           * of the buffers and begins asynchronously writing them. The
           * only way to wait for these asynchronous writes is to sleep
           * on the filesystem vnode which may stay busy for a long time
           * if the filesystem is active. So, instead, we make a second
           * pass over the dependencies blocking on each write. In the
           * usual case we will be blocking against a write that we
           * initiated, so when it is done the dependency will have been
           * resolved. Thus the second pass is expected to end quickly.
           * We give a brief window at the top of the loop to allow
           * any pending I/O to complete.
           */
          for (error = 0, waitfor = MNT_NOWAIT; ; ) {
                  if (error)
                          return (error);
                  FREE_LOCK(&lk);
                  ACQUIRE_LOCK(&lk);
                  if (inodedep_lookup(mp, ino, 0, &inodedep) == 0)
                          return (0);
                  if (flush_deplist(&inodedep->id_inoupdt, waitfor, &error) ||
                      flush_deplist(&inodedep->id_newinoupdt, waitfor, &error) ||
                      flush_deplist(&inodedep->id_extupdt, waitfor, &error) ||
                      flush_deplist(&inodedep->id_newextupdt, waitfor, &error))
                          continue;
                  /*
                   * If pass2, we are done, otherwise do pass 2.
                   */
                  if (waitfor == MNT_WAIT)
                          break;
                  waitfor = MNT_WAIT;
          }
          /*
           * Try freeing inodedep in case all dependencies have been removed.
           */
          if (inodedep_lookup(mp, ino, 0, &inodedep) != 0)
                  (void) free_inodedep(inodedep);
          return (0);
  }
  
  /*
   * Flush an inode dependency list.
   * Called with splbio blocked.
   */
  static int
  flush_deplist(listhead, waitfor, errorp)
          struct allocdirectlst *listhead;
          int waitfor;
          int *errorp;
  {
          struct allocdirect *adp;
          struct buf *bp;
  
          mtx_assert(&lk, MA_OWNED);
          TAILQ_FOREACH(adp, listhead, ad_next) {
                  if (adp->ad_state & DEPCOMPLETE)
                          continue;
                  bp = adp->ad_buf;
                  bp = getdirtybuf(bp, &lk, waitfor);
                  if (bp == NULL) {
                          if (waitfor == MNT_NOWAIT)
                                  continue;
                          return (1);
                  }
                  FREE_LOCK(&lk);
                  if (waitfor == MNT_NOWAIT) {
                          bawrite(bp);
                  } else if ((*errorp = bwrite(bp)) != 0) {
                          ACQUIRE_LOCK(&lk);
                          return (1);
                  }
                  ACQUIRE_LOCK(&lk);
                  return (1);
          }
          return (0);
  }
  
  /*
   * Eliminate a pagedep dependency by flushing out all its diradd dependencies.
   * Called with splbio blocked.
   */
  static int
  flush_pagedep_deps(pvp, mp, diraddhdp)
          struct vnode *pvp;
          struct mount *mp;
          struct diraddhd *diraddhdp;
  {
          struct inodedep *inodedep;
          struct ufsmount *ump;
          struct diradd *dap;
          struct vnode *vp;
          int error = 0;
          struct buf *bp;
          ino_t inum;
          struct worklist *wk;
  
          ump = VFSTOUFS(mp);
          while ((dap = LIST_FIRST(diraddhdp)) != NULL) {
                  /*
                   * Flush ourselves if this directory entry
                   * has a MKDIR_PARENT dependency.
                   */
                  if (dap->da_state & MKDIR_PARENT) {
                          FREE_LOCK(&lk);
                          if ((error = ffs_update(pvp, 1)) != 0)
                                  break;
                          ACQUIRE_LOCK(&lk);
                          /*
                           * If that cleared dependencies, go on to next.
                           */
                          if (dap != LIST_FIRST(diraddhdp))
                                  continue;
                          if (dap->da_state & MKDIR_PARENT)
                                  panic("flush_pagedep_deps: MKDIR_PARENT");
                  }
                  /*
                   * A newly allocated directory must have its "." and
                   * ".." entries written out before its name can be
                   * committed in its parent. We do not want or need
                   * the full semantics of a synchronous ffs_syncvnode as
                   * that may end up here again, once for each directory
                   * level in the filesystem. Instead, we push the blocks
                   * and wait for them to clear. We have to fsync twice
                   * because the first call may choose to defer blocks
                   * that still have dependencies, but deferral will
                   * happen at most once.
                   */
                  inum = dap->da_newinum;
                  if (dap->da_state & MKDIR_BODY) {
                          FREE_LOCK(&lk);
                          if ((error = ffs_vget(mp, inum, LK_EXCLUSIVE, &vp)))
                                  break;
                          if ((error=ffs_syncvnode(vp, MNT_NOWAIT)) ||
                              (error=ffs_syncvnode(vp, MNT_NOWAIT))) {
                                  vput(vp);
                                  break;
                          }
                          VI_LOCK(vp);
                          drain_output(vp);
                          /*
                           * If first block is still dirty with a D_MKDIR
                           * dependency then it needs to be written now.
                           */
                          for (;;) {
                                  error = 0;
                                  bp = gbincore(&vp->v_bufobj, 0);
                                  if (bp == NULL)
                                          break;  /* First block not present */
                                  error = BUF_LOCK(bp,
                                                   LK_EXCLUSIVE |
                                                   LK_SLEEPFAIL |
                                                   LK_INTERLOCK,
                                                   VI_MTX(vp));
                                  VI_LOCK(vp);
                                  if (error == ENOLCK)
                                          continue;       /* Slept, retry */
                                  if (error != 0)
                                          break;          /* Failed */
                                  if ((bp->b_flags & B_DELWRI) == 0) {
                                          BUF_UNLOCK(bp);
                                          break;  /* Buffer not dirty */
                                  }
                                  for (wk = LIST_FIRST(&bp->b_dep);
                                       wk != NULL;
                                       wk = LIST_NEXT(wk, wk_list))
                                          if (wk->wk_type == D_MKDIR)
                                                  break;
                                  if (wk == NULL)
                                          BUF_UNLOCK(bp); /* Dependency gone */
                                  else {
                                          /*
                                           * D_MKDIR dependency remains,
                                           * must write buffer to stable
                                           * storage.
                                           */
                                          VI_UNLOCK(vp);
                                          bremfree(bp);
                                          error = bwrite(bp);
                                          VI_LOCK(vp);
                                  }
                                  break;
                          }
                          VI_UNLOCK(vp);
                          vput(vp);
                          if (error != 0)
                                  break;  /* Flushing of first block failed */
                          ACQUIRE_LOCK(&lk);
                          /*
                           * If that cleared dependencies, go on to next.
                           */
                          if (dap != LIST_FIRST(diraddhdp))
                                  continue;
                          if (dap->da_state & MKDIR_BODY)
                                  panic("flush_pagedep_deps: MKDIR_BODY");
                  }
                  /*
                   * Flush the inode on which the directory entry depends.
                   * Having accounted for MKDIR_PARENT and MKDIR_BODY above,
                   * the only remaining dependency is that the updated inode
                   * count must get pushed to disk. The inode has already
                   * been pushed into its inode buffer (via VOP_UPDATE) at
                   * the time of the reference count change. So we need only
                   * locate that buffer, ensure that there will be no rollback
                   * caused by a bitmap dependency, then write the inode buffer.
                   */
  retry:
                  if (inodedep_lookup(UFSTOVFS(ump), inum, 0, &inodedep) == 0)
                          panic("flush_pagedep_deps: lost inode");
                  /*
                   * If the inode still has bitmap dependencies,
                   * push them to disk.
                   */
                  if ((inodedep->id_state & DEPCOMPLETE) == 0) {
                          bp = inodedep->id_buf;
                          bp = getdirtybuf(bp, &lk, MNT_WAIT);
                          if (bp == NULL)
                                  goto retry;
                          FREE_LOCK(&lk);
                          if ((error = bwrite(bp)) != 0)
                                  break;
                          ACQUIRE_LOCK(&lk);
                          if (dap != LIST_FIRST(diraddhdp))
                                  continue;
                  }
                  /*
                   * If the inode is still sitting in a buffer waiting
                   * to be written, push it to disk.
                   */
                  FREE_LOCK(&lk);
                  if ((error = bread(ump->um_devvp,
                      fsbtodb(ump->um_fs, ino_to_fsba(ump->um_fs, inum)),
                      (int)ump->um_fs->fs_bsize, NOCRED, &bp)) != 0) {
                          brelse(bp);
                          break;
                  }
                  if ((error = bwrite(bp)) != 0)
                          break;
                  ACQUIRE_LOCK(&lk);
                  /*
                   * If we have failed to get rid of all the dependencies
                   * then something is seriously wrong.
                   */
                  if (dap == LIST_FIRST(diraddhdp))
                          panic("flush_pagedep_deps: flush failed");
          }
          if (error)
                  ACQUIRE_LOCK(&lk);
          return (error);
  }
  
  /*
   * A large burst of file addition or deletion activity can drive the
   * memory load excessively high. First attempt to slow things down
   * using the techniques below. If that fails, this routine requests
   * the offending operations to fall back to running synchronously
   * until the memory load returns to a reasonable level.
   */
  int
  softdep_slowdown(vp)
          struct vnode *vp;
  {
          int max_softdeps_hard;
  
          ACQUIRE_LOCK(&lk);
          max_softdeps_hard = max_softdeps * 11 / 10;
          if (num_dirrem < max_softdeps_hard / 2 &&
              num_inodedep < max_softdeps_hard &&
              VFSTOUFS(vp->v_mount)->um_numindirdeps < maxindirdeps &&
              num_freeblkdep < max_softdeps_hard) {
                  FREE_LOCK(&lk);
                  return (0);
          }
          if (VFSTOUFS(vp->v_mount)->um_numindirdeps >= maxindirdeps)
                  softdep_speedup();
          stat_sync_limit_hit += 1;
          FREE_LOCK(&lk);
          return (1);
  }
  
  /*
   * Called by the allocation routines when they are about to fail
   * in the hope that we can free up some disk space.
   * 
   * First check to see if the work list has anything on it. If it has,
   * clean up entries until we successfully free some space. Because this
   * process holds inodes locked, we cannot handle any remove requests
   * that might block on a locked inode as that could lead to deadlock.
   * If the worklist yields no free space, encourage the syncer daemon
   * to help us. In no event will we try for longer than tickdelay seconds.
   */
  int
  softdep_request_cleanup(fs, vp)
          struct fs *fs;
          struct vnode *vp;
  {
          struct ufsmount *ump;
          long starttime;
          ufs2_daddr_t needed;
          int error;
  
          ump = VTOI(vp)->i_ump;
          mtx_assert(UFS_MTX(ump), MA_OWNED);
          needed = fs->fs_cstotal.cs_nbfree + fs->fs_contigsumsize;
          starttime = time_second + tickdelay;
          /*
           * If we are being called because of a process doing a
           * copy-on-write, then it is not safe to update the vnode
           * as we may recurse into the copy-on-write routine.
           */
          if (!(curthread->td_pflags & TDP_COWINPROGRESS)) {
                  UFS_UNLOCK(ump);
                  error = ffs_update(vp, 1);
                  UFS_LOCK(ump);
                  if (error != 0)
                          return (0);
          }
          while (fs->fs_pendingblocks > 0 && fs->fs_cstotal.cs_nbfree <= needed) {
                  if (time_second > starttime)
                          return (0);
                  UFS_UNLOCK(ump);
                  ACQUIRE_LOCK(&lk);
                  if (ump->softdep_on_worklist > 0 &&
                      process_worklist_item(UFSTOVFS(ump), LK_NOWAIT) != -1) {
                          stat_worklist_push += 1;
                          FREE_LOCK(&lk);
                          UFS_LOCK(ump);
                          continue;
                  }
                  request_cleanup(UFSTOVFS(ump), FLUSH_REMOVE_WAIT);
                  FREE_LOCK(&lk);
                  UFS_LOCK(ump);
          }
          return (1);
  }
  
  /*
   * If memory utilization has gotten too high, deliberately slow things
   * down and speed up the I/O processing.
   */
  extern struct thread *syncertd;
  static int
  request_cleanup(mp, resource)
          struct mount *mp;
          int resource;
  {
          struct thread *td = curthread;
          struct ufsmount *ump;
  
          mtx_assert(&lk, MA_OWNED);
          /*
           * We never hold up the filesystem syncer or buf daemon.
           */
          if (td->td_pflags & (TDP_SOFTDEP|TDP_NORUNNINGBUF))
                  return (0);
          ump = VFSTOUFS(mp);
          /*
           * First check to see if the work list has gotten backlogged.
           * If it has, co-opt this process to help clean up two entries.
           * Because this process may hold inodes locked, we cannot
           * handle any remove requests that might block on a locked
           * inode as that could lead to deadlock.  We set TDP_SOFTDEP
           * to avoid recursively processing the worklist.
           */
          if (ump->softdep_on_worklist > max_softdeps / 10) {
                  td->td_pflags |= TDP_SOFTDEP;
                  process_worklist_item(mp, LK_NOWAIT);
                  process_worklist_item(mp, LK_NOWAIT);
                  td->td_pflags &= ~TDP_SOFTDEP;
                  stat_worklist_push += 2;
                  return(1);
          }
          /*
           * Next, we attempt to speed up the syncer process. If that
           * is successful, then we allow the process to continue.
           */
          if (softdep_speedup() && resource != FLUSH_REMOVE_WAIT)
                  return(0);
          /*
           * If we are resource constrained on inode dependencies, try
           * flushing some dirty inodes. Otherwise, we are constrained
           * by file deletions, so try accelerating flushes of directories
           * with removal dependencies. We would like to do the cleanup
           * here, but we probably hold an inode locked at this point and 
           * that might deadlock against one that we try to clean. So,
           * the best that we can do is request the syncer daemon to do
           * the cleanup for us.
           */
          switch (resource) {
  
          case FLUSH_INODES:
                  stat_ino_limit_push += 1;
                  req_clear_inodedeps += 1;
                  stat_countp = &stat_ino_limit_hit;
                  break;
  
          case FLUSH_REMOVE:
          case FLUSH_REMOVE_WAIT:
                  stat_blk_limit_push += 1;
                  req_clear_remove += 1;
                  stat_countp = &stat_blk_limit_hit;
                  break;
  
          default:
                  panic("request_cleanup: unknown type");
          }
          /*
           * Hopefully the syncer daemon will catch up and awaken us.
           * We wait at most tickdelay before proceeding in any case.
           */
          proc_waiting += 1;
          if (handle.callout == NULL)
                  handle = timeout(pause_timer, 0, tickdelay > 2 ? tickdelay : 2);
          msleep((caddr_t)&proc_waiting, &lk, PPAUSE, "softupdate", 0);
          proc_waiting -= 1;
          return (1);
  }
  
  /*
   * Awaken processes pausing in request_cleanup and clear proc_waiting
   * to indicate that there is no longer a timer running.
   */
  static void
  pause_timer(arg)
          void *arg;
  {
  
          ACQUIRE_LOCK(&lk);
          *stat_countp += 1;
          wakeup_one(&proc_waiting);
          if (proc_waiting > 0)
                  handle = timeout(pause_timer, 0, tickdelay > 2 ? tickdelay : 2);
          else
                  handle.callout = NULL;
          FREE_LOCK(&lk);
  }
  
  /*
   * Flush out a directory with at least one removal dependency in an effort to
   * reduce the number of dirrem, freefile, and freeblks dependency structures.
   */
  static void
  clear_remove(td)
          struct thread *td;
  {
          struct pagedep_hashhead *pagedephd;
          struct pagedep *pagedep;
          static int next = 0;
          struct mount *mp;
          struct vnode *vp;
          int error, cnt;
          ino_t ino;
  
          mtx_assert(&lk, MA_OWNED);
  
          for (cnt = 0; cnt < pagedep_hash; cnt++) {
                  pagedephd = &pagedep_hashtbl[next++];
                  if (next >= pagedep_hash)
                          next = 0;
                  LIST_FOREACH(pagedep, pagedephd, pd_hash) {
                          if (LIST_EMPTY(&pagedep->pd_dirremhd))
                                  continue;
                          mp = pagedep->pd_list.wk_mp;
                          ino = pagedep->pd_ino;
                          if (vn_start_write(NULL, &mp, V_NOWAIT) != 0)
                                  continue;
                          FREE_LOCK(&lk);
                          if ((error = ffs_vget(mp, ino, LK_EXCLUSIVE, &vp))) {
                                  softdep_error("clear_remove: vget", error);
                                  vn_finished_write(mp);
                                  ACQUIRE_LOCK(&lk);
                                  return;
                          }
                          if ((error = ffs_syncvnode(vp, MNT_NOWAIT)))
                                  softdep_error("clear_remove: fsync", error);
                          VI_LOCK(vp);
                          drain_output(vp);
                          VI_UNLOCK(vp);
                          vput(vp);
                          vn_finished_write(mp);
                          ACQUIRE_LOCK(&lk);
                          return;
                  }
          }
  }
  
  /*
   * Clear out a block of dirty inodes in an effort to reduce
   * the number of inodedep dependency structures.
   */
  static void
  clear_inodedeps(td)
          struct thread *td;
  {
          struct inodedep_hashhead *inodedephd;
          struct inodedep *inodedep;
          static int next = 0;
          struct mount *mp;
          struct vnode *vp;
          struct fs *fs;
          int error, cnt;
          ino_t firstino, lastino, ino;
  
          mtx_assert(&lk, MA_OWNED);
          /*
           * Pick a random inode dependency to be cleared.
           * We will then gather up all the inodes in its block 
           * that have dependencies and flush them out.
           */
          for (cnt = 0; cnt < inodedep_hash; cnt++) {
                  inodedephd = &inodedep_hashtbl[next++];
                  if (next >= inodedep_hash)
                          next = 0;
                  if ((inodedep = LIST_FIRST(inodedephd)) != NULL)
                          break;
          }
          if (inodedep == NULL)
                  return;
          fs = inodedep->id_fs;
          mp = inodedep->id_list.wk_mp;
          /*
           * Find the last inode in the block with dependencies.
           */
          firstino = inodedep->id_ino & ~(INOPB(fs) - 1);
          for (lastino = firstino + INOPB(fs) - 1; lastino > firstino; lastino--)
                  if (inodedep_lookup(mp, lastino, 0, &inodedep) != 0)
                          break;
          /*
           * Asynchronously push all but the last inode with dependencies.
           * Synchronously push the last inode with dependencies to ensure
           * that the inode block gets written to free up the inodedeps.
           */
          for (ino = firstino; ino <= lastino; ino++) {
                  if (inodedep_lookup(mp, ino, 0, &inodedep) == 0)
                          continue;
                  if (vn_start_write(NULL, &mp, V_NOWAIT) != 0)
                          continue;
                  FREE_LOCK(&lk);
                  if ((error = ffs_vget(mp, ino, LK_EXCLUSIVE, &vp)) != 0) {
                          softdep_error("clear_inodedeps: vget", error);
                          vn_finished_write(mp);
                          ACQUIRE_LOCK(&lk);
                          return;
                  }
                  if (ino == lastino) {
                          if ((error = ffs_syncvnode(vp, MNT_WAIT)))
                                  softdep_error("clear_inodedeps: fsync1", error);
                  } else {
                          if ((error = ffs_syncvnode(vp, MNT_NOWAIT)))
                                  softdep_error("clear_inodedeps: fsync2", error);
                          VI_LOCK(vp);
                          drain_output(vp);
                          VI_UNLOCK(vp);
                  }
                  vput(vp);
                  vn_finished_write(mp);
                  ACQUIRE_LOCK(&lk);
          }
  }
  
  /*
   * Function to determine if the buffer has outstanding dependencies
   * that will cause a roll-back if the buffer is written. If wantcount
   * is set, return number of dependencies, otherwise just yes or no.
   */
  static int
  softdep_count_dependencies(bp, wantcount)
          struct buf *bp;
          int wantcount;
  {
          struct worklist *wk;
          struct inodedep *inodedep;
          struct indirdep *indirdep;
          struct allocindir *aip;
          struct pagedep *pagedep;
          struct diradd *dap;
          int i, retval;
  
          retval = 0;
          ACQUIRE_LOCK(&lk);
          LIST_FOREACH(wk, &bp->b_dep, wk_list) {
                  switch (wk->wk_type) {
  
                  case D_INODEDEP:
                          inodedep = WK_INODEDEP(wk);
                          if ((inodedep->id_state & DEPCOMPLETE) == 0) {
                                  /* bitmap allocation dependency */
                                  retval += 1;
                                  if (!wantcount)
                                          goto out;
                          }
                          if (TAILQ_FIRST(&inodedep->id_inoupdt)) {
                                  /* direct block pointer dependency */
                                  retval += 1;
                                  if (!wantcount)
                                          goto out;
                          }
                          if (TAILQ_FIRST(&inodedep->id_extupdt)) {
                                  /* direct block pointer dependency */
                                  retval += 1;
                                  if (!wantcount)
                                          goto out;
                          }
                          continue;
  
                  case D_INDIRDEP:
                          indirdep = WK_INDIRDEP(wk);
  
                          LIST_FOREACH(aip, &indirdep->ir_deplisthd, ai_next) {
                                  /* indirect block pointer dependency */
                                  retval += 1;
                                  if (!wantcount)
                                          goto out;
                          }
                          continue;
  
                  case D_PAGEDEP:
                          pagedep = WK_PAGEDEP(wk);
                          for (i = 0; i < DAHASHSZ; i++) {
  
                                  LIST_FOREACH(dap, &pagedep->pd_diraddhd[i], da_pdlist) {
                                          /* directory entry dependency */
                                          retval += 1;
                                          if (!wantcount)
                                                  goto out;
                                  }
                          }
                          continue;
  
                  case D_BMSAFEMAP:
                  case D_ALLOCDIRECT:
                  case D_ALLOCINDIR:
                  case D_MKDIR:
                          /* never a dependency on these blocks */
                          continue;
  
                  default:
                          panic("softdep_check_for_rollback: Unexpected type %s",
                              TYPENAME(wk->wk_type));
                          /* NOTREACHED */
                  }
          }
  out:
          FREE_LOCK(&lk);
          return retval;
  }
  
  /*
   * Acquire exclusive access to a buffer.
   * Must be called with a locked mtx parameter.
   * Return acquired buffer or NULL on failure.
   */
  static struct buf *
  getdirtybuf(bp, mtx, waitfor)
          struct buf *bp;
          struct mtx *mtx;
          int waitfor;
  {
          int error;
  
          mtx_assert(mtx, MA_OWNED);
          if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT, NULL) != 0) {
                  if (waitfor != MNT_WAIT)
                          return (NULL);
                  error = BUF_LOCK(bp,
                      LK_EXCLUSIVE | LK_SLEEPFAIL | LK_INTERLOCK, mtx);
                  /*
                   * Even if we sucessfully acquire bp here, we have dropped
                   * mtx, which may violates our guarantee.
                   */
                  if (error == 0)
                          BUF_UNLOCK(bp);
                  else if (error != ENOLCK)
                          panic("getdirtybuf: inconsistent lock: %d", error);
                  mtx_lock(mtx);
                  return (NULL);
          }
          if ((bp->b_vflags & BV_BKGRDINPROG) != 0) {
                  if (mtx == &lk && waitfor == MNT_WAIT) {
                          mtx_unlock(mtx);
                          BO_LOCK(bp->b_bufobj);
                          BUF_UNLOCK(bp);
                          if ((bp->b_vflags & BV_BKGRDINPROG) != 0) {
                                  bp->b_vflags |= BV_BKGRDWAIT;
                                  msleep(&bp->b_xflags, BO_MTX(bp->b_bufobj),
                                         PRIBIO | PDROP, "getbuf", 0);
                          } else
                                  BO_UNLOCK(bp->b_bufobj);
                          mtx_lock(mtx);
                          return (NULL);
                  }
                  BUF_UNLOCK(bp);
                  if (waitfor != MNT_WAIT)
                          return (NULL);
                  /*
                   * The mtx argument must be bp->b_vp's mutex in
                   * this case.
                   */
  #ifdef  DEBUG_VFS_LOCKS
                  if (bp->b_vp->v_type != VCHR)
                          ASSERT_VI_LOCKED(bp->b_vp, "getdirtybuf");
  #endif
                  bp->b_vflags |= BV_BKGRDWAIT;
                  msleep(&bp->b_xflags, mtx, PRIBIO, "getbuf", 0);
                  return (NULL);
          }
          if ((bp->b_flags & B_DELWRI) == 0) {
                  BUF_UNLOCK(bp);
                  return (NULL);
          }
          bremfree(bp);
          return (bp);
  }
  
  
  /*
   * Check if it is safe to suspend the file system now.  On entry,
   * the vnode interlock for devvp should be held.  Return 0 with
   * the mount interlock held if the file system can be suspended now,
   * otherwise return EAGAIN with the mount interlock held.
   */
  int
  softdep_check_suspend(struct mount *mp,
                        struct vnode *devvp,
                        int softdep_deps,
                        int softdep_accdeps,
                        int secondary_writes,
                        int secondary_accwrites)
  {
          struct bufobj *bo;
          struct ufsmount *ump;
          int error;
  
          ASSERT_VI_LOCKED(devvp, "softdep_check_suspend");
          ump = VFSTOUFS(mp);
          bo = &devvp->v_bufobj;
  
          for (;;) {
                  if (!TRY_ACQUIRE_LOCK(&lk)) {
                          VI_UNLOCK(devvp);
                          ACQUIRE_LOCK(&lk);
                          FREE_LOCK(&lk);
                          VI_LOCK(devvp);
                          continue;
                  }
                  if (!MNT_ITRYLOCK(mp)) {
                          FREE_LOCK(&lk);
                          VI_UNLOCK(devvp);
                          MNT_ILOCK(mp);
                          MNT_IUNLOCK(mp);
                          VI_LOCK(devvp);
                          continue;
                  }
                  if (mp->mnt_secondary_writes != 0) {
                          FREE_LOCK(&lk);
                          VI_UNLOCK(devvp);
                          msleep(&mp->mnt_secondary_writes,
                                 MNT_MTX(mp),
                                 (PUSER - 1) | PDROP, "secwr", 0);
                          VI_LOCK(devvp);
                          continue;
                  }
                  break;
          }
  
          /*
           * Reasons for needing more work before suspend:
           * - Dirty buffers on devvp.
           * - Softdep activity occurred after start of vnode sync loop
           * - Secondary writes occurred after start of vnode sync loop
           */
          error = 0;
          if (bo->bo_numoutput > 0 ||
              bo->bo_dirty.bv_cnt > 0 ||
              softdep_deps != 0 ||
              ump->softdep_deps != 0 ||
              softdep_accdeps != ump->softdep_accdeps ||
              secondary_writes != 0 ||
              mp->mnt_secondary_writes != 0 ||
              secondary_accwrites != mp->mnt_secondary_accwrites)
                  error = EAGAIN;
          FREE_LOCK(&lk);
          VI_UNLOCK(devvp);
          return (error);
  }
  
  
  /*
   * Get the number of dependency structures for the file system, both
   * the current number and the total number allocated.  These will
   * later be used to detect that softdep processing has occurred.
   */
  void
  softdep_get_depcounts(struct mount *mp,
                        int *softdep_depsp,
                        int *softdep_accdepsp)
  {
          struct ufsmount *ump;
  
          ump = VFSTOUFS(mp);
          ACQUIRE_LOCK(&lk);
          *softdep_depsp = ump->softdep_deps;
          *softdep_accdepsp = ump->softdep_accdeps;
          FREE_LOCK(&lk);
  }
  
  /*
   * Wait for pending output on a vnode to complete.
   * Must be called with vnode lock and interlock locked.
   *
   * XXX: Should just be a call to bufobj_wwait().
   */
  static void
  drain_output(vp)
          struct vnode *vp;
  {
          ASSERT_VOP_LOCKED(vp, "drain_output");
          ASSERT_VI_LOCKED(vp, "drain_output");
  
          while (vp->v_bufobj.bo_numoutput) {
                  vp->v_bufobj.bo_flag |= BO_WWAIT;
                  msleep((caddr_t)&vp->v_bufobj.bo_numoutput,
                      VI_MTX(vp), PRIBIO + 1, "drainvp", 0);
          }
  }
  
  /*
   * Called whenever a buffer that is being invalidated or reallocated
   * contains dependencies. This should only happen if an I/O error has
   * occurred. The routine is called with the buffer locked.
   */ 
  static void
  softdep_deallocate_dependencies(bp)
          struct buf *bp;
  {
  
          if ((bp->b_ioflags & BIO_ERROR) == 0)
                  panic("softdep_deallocate_dependencies: dangling deps");
          softdep_error(bp->b_vp->v_mount->mnt_stat.f_mntonname, bp->b_error);
          panic("softdep_deallocate_dependencies: unrecovered I/O error");
  }
  
  /*
   * Function to handle asynchronous write errors in the filesystem.
   */
  static void
  softdep_error(func, error)
          char *func;
          int error;
  {
  
          /* XXX should do something better! */
          printf("%s: got error %d while accessing filesystem\n", func, error);
  }
  
  #endif /* SOFTUPDATES */