FreeBSD/Linux Kernel Cross Reference
sys/kern/vfs_wapbl.c

     /*      $NetBSD: vfs_wapbl.c,v 1.112 2022/04/09 23:38:33 riastradh Exp $        */
     
     /*-
      * Copyright (c) 2003, 2008, 2009 The NetBSD Foundation, Inc.
      * All rights reserved.
      *
      * This code is derived from software contributed to The NetBSD Foundation
      * by Wasabi Systems, Inc.
      *
     * 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 THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     * ``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 THE FOUNDATION OR CONTRIBUTORS
     * 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.
     */
    
    /*
     * This implements file system independent write ahead filesystem logging.
     */
    
    #define WAPBL_INTERNAL
    
    #include <sys/cdefs.h>
    __KERNEL_RCSID(0, "$NetBSD: vfs_wapbl.c,v 1.112 2022/04/09 23:38:33 riastradh Exp $");
    
    #include <sys/param.h>
    #include <sys/bitops.h>
    #include <sys/time.h>
    #include <sys/wapbl.h>
    #include <sys/wapbl_replay.h>
    
    #ifdef _KERNEL
    
    #include <sys/atomic.h>
    #include <sys/conf.h>
    #include <sys/evcnt.h>
    #include <sys/file.h>
    #include <sys/kauth.h>
    #include <sys/kernel.h>
    #include <sys/module.h>
    #include <sys/mount.h>
    #include <sys/mutex.h>
    #include <sys/namei.h>
    #include <sys/proc.h>
    #include <sys/resourcevar.h>
    #include <sys/sysctl.h>
    #include <sys/uio.h>
    #include <sys/vnode.h>
    
    #include <miscfs/specfs/specdev.h>
    
    #define wapbl_alloc(s) kmem_alloc((s), KM_SLEEP)
    #define wapbl_free(a, s) kmem_free((a), (s))
    #define wapbl_calloc(n, s) kmem_zalloc((n)*(s), KM_SLEEP)
    
    static int wapbl_flush_disk_cache = 1;
    static int wapbl_verbose_commit = 0;
    static int wapbl_allow_dpofua = 0;      /* switched off by default for now */
    static int wapbl_journal_iobufs = 4;
    
    static inline size_t wapbl_space_free(size_t, off_t, off_t);
    
    #else /* !_KERNEL */
    
    #include <assert.h>
    #include <errno.h>
    #include <stdbool.h>
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    
    #define KDASSERT(x) assert(x)
    #define KASSERT(x) assert(x)
    #define wapbl_alloc(s) malloc(s)
    #define wapbl_free(a, s) free(a)
    #define wapbl_calloc(n, s) calloc((n), (s))
    
    #endif /* !_KERNEL */
    
    /*
     * INTERNAL DATA STRUCTURES
     */
    
    /*
    * This structure holds per-mount log information.
    *
    * Legend:      a = atomic access only
    *              r = read-only after init
    *              l = rwlock held
    *              m = mutex held
    *              lm = rwlock held writing or mutex held
    *              u = unlocked access ok
    *              b = bufcache_lock held
    */
   LIST_HEAD(wapbl_ino_head, wapbl_ino);
   struct wapbl {
           struct vnode *wl_logvp; /* r:   log here */
           struct vnode *wl_devvp; /* r:   log on this device */
           struct mount *wl_mount; /* r:   mountpoint wl is associated with */
           daddr_t wl_logpbn;      /* r:   Physical block number of start of log */
           int wl_log_dev_bshift;  /* r:   logarithm of device block size of log
                                           device */
           int wl_fs_dev_bshift;   /* r:   logarithm of device block size of
                                           filesystem device */
   
           unsigned wl_lock_count; /* m:   Count of transactions in progress */
   
           size_t wl_circ_size;    /* r:   Number of bytes in buffer of log */
           size_t wl_circ_off;     /* r:   Number of bytes reserved at start */
   
           size_t wl_bufcount_max; /* r:   Number of buffers reserved for log */
           size_t wl_bufbytes_max; /* r:   Number of buf bytes reserved for log */
   
           off_t wl_head;          /* l:   Byte offset of log head */
           off_t wl_tail;          /* l:   Byte offset of log tail */
           /*
            * WAPBL log layout, stored on wl_devvp at wl_logpbn:
            *
            *  ___________________ wl_circ_size __________________
            * /                                                   \
            * +---------+---------+-------+--------------+--------+
            * [ commit0 | commit1 | CCWCW | EEEEEEEEEEEE | CCCWCW ]
            * +---------+---------+-------+--------------+--------+
            *       wl_circ_off --^       ^-- wl_head    ^-- wl_tail
            *
            * commit0 and commit1 are commit headers.  A commit header has
            * a generation number, indicating which of the two headers is
            * more recent, and an assignment of head and tail pointers.
            * The rest is a circular queue of log records, starting at
            * the byte offset wl_circ_off.
            *
            * E marks empty space for records.
            * W marks records for block writes issued but waiting.
            * C marks completed records.
            *
            * wapbl_flush writes new records to empty `E' spaces after
            * wl_head from the current transaction in memory.
            *
            * wapbl_truncate advances wl_tail past any completed `C'
            * records, freeing them up for use.
            *
            * head == tail == 0 means log is empty.
            * head == tail != 0 means log is full.
            *
            * See assertions in wapbl_advance() for other boundary
            * conditions.
            *
            * Only wapbl_flush moves the head, except when wapbl_truncate
            * sets it to 0 to indicate that the log is empty.
            *
            * Only wapbl_truncate moves the tail, except when wapbl_flush
            * sets it to wl_circ_off to indicate that the log is full.
            */
   
           struct wapbl_wc_header *wl_wc_header;   /* l    */
           void *wl_wc_scratch;    /* l:   scratch space (XXX: por que?!?) */
   
           kmutex_t wl_mtx;        /* u:   short-term lock */
           krwlock_t wl_rwlock;    /* u:   File system transaction lock */
   
           /*
            * Must be held while accessing
            * wl_count or wl_bufs or head or tail
            */
   
   #if _KERNEL
           /*
            * Callback called from within the flush routine to flush any extra
            * bits.  Note that flush may be skipped without calling this if
            * there are no outstanding buffers in the transaction.
            */
           wapbl_flush_fn_t wl_flush;      /* r    */
           wapbl_flush_fn_t wl_flush_abort;/* r    */
   
           /* Event counters */
           char wl_ev_group[EVCNT_STRING_MAX];     /* r    */
           struct evcnt wl_ev_commit;              /* l    */
           struct evcnt wl_ev_journalwrite;        /* l    */
           struct evcnt wl_ev_jbufs_bio_nowait;    /* l    */
           struct evcnt wl_ev_metawrite;           /* lm   */
           struct evcnt wl_ev_cacheflush;          /* l    */
   #endif
   
           size_t wl_bufbytes;     /* m:   Byte count of pages in wl_bufs */
           size_t wl_bufcount;     /* m:   Count of buffers in wl_bufs */
           size_t wl_bcount;       /* m:   Total bcount of wl_bufs */
   
           TAILQ_HEAD(, buf) wl_bufs; /* m: Buffers in current transaction */
   
           kcondvar_t wl_reclaimable_cv;   /* m (obviously) */
           size_t wl_reclaimable_bytes; /* m:      Amount of space available for
                                                   reclamation by truncate */
           int wl_error_count;     /* m:   # of wl_entries with errors */
           size_t wl_reserved_bytes; /* never truncate log smaller than this */
   
   #ifdef WAPBL_DEBUG_BUFBYTES
           size_t wl_unsynced_bufbytes; /* Byte count of unsynced buffers */
   #endif
   
   #if _KERNEL
           int wl_brperjblock;     /* r Block records per journal block */
   #endif
   
           TAILQ_HEAD(, wapbl_dealloc) wl_dealloclist;     /* lm:  list head */
           int wl_dealloccnt;                              /* lm:  total count */
           int wl_dealloclim;                              /* r:   max count */
   
           /* hashtable of inode numbers for allocated but unlinked inodes */
           /* synch ??? */
           struct wapbl_ino_head *wl_inohash;
           u_long wl_inohashmask;
           int wl_inohashcnt;
   
           SIMPLEQ_HEAD(, wapbl_entry) wl_entries; /* m: On disk transaction
                                                      accounting */
   
           /* buffers for wapbl_buffered_write() */
           TAILQ_HEAD(, buf) wl_iobufs;            /* l: Free or filling bufs */
           TAILQ_HEAD(, buf) wl_iobufs_busy;       /* l: In-transit bufs */
   
           int wl_dkcache;         /* r:   disk cache flags */
   #define WAPBL_USE_FUA(wl)       \
                   (wapbl_allow_dpofua && ISSET((wl)->wl_dkcache, DKCACHE_FUA))
   #define WAPBL_JFLAGS(wl)        \
                   (WAPBL_USE_FUA(wl) ? (wl)->wl_jwrite_flags : 0)
   #define WAPBL_JDATA_FLAGS(wl)   \
                   (WAPBL_JFLAGS(wl) & B_MEDIA_DPO)        /* only DPO */
           int wl_jwrite_flags;    /* r:   journal write flags */
   };
   
   #ifdef WAPBL_DEBUG_PRINT
   int wapbl_debug_print = WAPBL_DEBUG_PRINT;
   #endif
   
   /****************************************************************/
   #ifdef _KERNEL
   
   #ifdef WAPBL_DEBUG
   struct wapbl *wapbl_debug_wl;
   #endif
   
   static int wapbl_write_commit(struct wapbl *wl, off_t head, off_t tail);
   static int wapbl_write_blocks(struct wapbl *wl, off_t *offp);
   static int wapbl_write_revocations(struct wapbl *wl, off_t *offp);
   static int wapbl_write_inodes(struct wapbl *wl, off_t *offp);
   #endif /* _KERNEL */
   
   static int wapbl_replay_process(struct wapbl_replay *wr, off_t, off_t);
   
   static inline size_t wapbl_space_used(size_t avail, off_t head,
           off_t tail);
   
   #ifdef _KERNEL
   
   static struct pool wapbl_entry_pool;
   static struct pool wapbl_dealloc_pool;
   
   #define WAPBL_INODETRK_SIZE 83
   static int wapbl_ino_pool_refcount;
   static struct pool wapbl_ino_pool;
   struct wapbl_ino {
           LIST_ENTRY(wapbl_ino) wi_hash;
           ino_t wi_ino;
           mode_t wi_mode;
   };
   
   static void wapbl_inodetrk_init(struct wapbl *wl, u_int size);
   static void wapbl_inodetrk_free(struct wapbl *wl);
   static struct wapbl_ino *wapbl_inodetrk_get(struct wapbl *wl, ino_t ino);
   
   static size_t wapbl_transaction_len(struct wapbl *wl);
   static inline size_t wapbl_transaction_inodes_len(struct wapbl *wl);
   
   static void wapbl_deallocation_free(struct wapbl *, struct wapbl_dealloc *,
           bool);
   
   static void wapbl_evcnt_init(struct wapbl *);
   static void wapbl_evcnt_free(struct wapbl *);
   
   static void wapbl_dkcache_init(struct wapbl *);
   
   #if 0
   int wapbl_replay_verify(struct wapbl_replay *, struct vnode *);
   #endif
   
   static int wapbl_replay_isopen1(struct wapbl_replay *);
   
   const struct wapbl_ops wapbl_ops = {
           .wo_wapbl_discard       = wapbl_discard,
           .wo_wapbl_replay_isopen = wapbl_replay_isopen1,
           .wo_wapbl_replay_can_read = wapbl_replay_can_read,
           .wo_wapbl_replay_read   = wapbl_replay_read,
           .wo_wapbl_add_buf       = wapbl_add_buf,
           .wo_wapbl_remove_buf    = wapbl_remove_buf,
           .wo_wapbl_resize_buf    = wapbl_resize_buf,
           .wo_wapbl_begin         = wapbl_begin,
           .wo_wapbl_end           = wapbl_end,
           .wo_wapbl_junlock_assert= wapbl_junlock_assert,
           .wo_wapbl_jlock_assert  = wapbl_jlock_assert,
   
           /* XXX: the following is only used to say "this is a wapbl buf" */
           .wo_wapbl_biodone       = wapbl_biodone,
   };
   
   SYSCTL_SETUP(wapbl_sysctl_init, "wapbl sysctl")
   {
           int rv;
           const struct sysctlnode *rnode, *cnode;
   
           rv = sysctl_createv(clog, 0, NULL, &rnode,
                          CTLFLAG_PERMANENT,
                          CTLTYPE_NODE, "wapbl",
                          SYSCTL_DESCR("WAPBL journaling options"),
                          NULL, 0, NULL, 0,
                          CTL_VFS, CTL_CREATE, CTL_EOL);
           if (rv)
                   return;
   
           rv = sysctl_createv(clog, 0, &rnode, &cnode,
                          CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                          CTLTYPE_INT, "flush_disk_cache",
                          SYSCTL_DESCR("flush disk cache"),
                          NULL, 0, &wapbl_flush_disk_cache, 0,
                          CTL_CREATE, CTL_EOL);
           if (rv)
                   return;
   
           rv = sysctl_createv(clog, 0, &rnode, &cnode,
                          CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                          CTLTYPE_INT, "verbose_commit",
                          SYSCTL_DESCR("show time and size of wapbl log commits"),
                          NULL, 0, &wapbl_verbose_commit, 0,
                          CTL_CREATE, CTL_EOL);
           if (rv)
                   return;
   
           rv = sysctl_createv(clog, 0, &rnode, &cnode,
                          CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                          CTLTYPE_INT, "allow_dpofua",
                          SYSCTL_DESCR("allow use of FUA/DPO instead of cache flush if available"),
                          NULL, 0, &wapbl_allow_dpofua, 0,
                          CTL_CREATE, CTL_EOL);
           if (rv)
                   return;
   
           rv = sysctl_createv(clog, 0, &rnode, &cnode,
                          CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                          CTLTYPE_INT, "journal_iobufs",
                          SYSCTL_DESCR("count of bufs used for journal I/O (max async count)"),
                          NULL, 0, &wapbl_journal_iobufs, 0,
                          CTL_CREATE, CTL_EOL);
           if (rv)
                   return;
   
           return;
   }
   
   static void
   wapbl_init(void)
   {
   
           pool_init(&wapbl_entry_pool, sizeof(struct wapbl_entry), 0, 0, 0,
               "wapblentrypl", &pool_allocator_kmem, IPL_VM);
           pool_init(&wapbl_dealloc_pool, sizeof(struct wapbl_dealloc), 0, 0, 0,
               "wapbldealloc", &pool_allocator_nointr, IPL_NONE);
   }
   
   static int
   wapbl_fini(void)
   {
   
           pool_destroy(&wapbl_dealloc_pool);
           pool_destroy(&wapbl_entry_pool);
   
           return 0;
   }
   
   static void
   wapbl_evcnt_init(struct wapbl *wl)
   {
           snprintf(wl->wl_ev_group, sizeof(wl->wl_ev_group),
               "wapbl fsid 0x%x/0x%x",
               wl->wl_mount->mnt_stat.f_fsidx.__fsid_val[0],
               wl->wl_mount->mnt_stat.f_fsidx.__fsid_val[1]
           );
   
           evcnt_attach_dynamic(&wl->wl_ev_commit, EVCNT_TYPE_MISC,
               NULL, wl->wl_ev_group, "commit");
           evcnt_attach_dynamic(&wl->wl_ev_journalwrite, EVCNT_TYPE_MISC,
               NULL, wl->wl_ev_group, "journal write total");
           evcnt_attach_dynamic(&wl->wl_ev_jbufs_bio_nowait, EVCNT_TYPE_MISC,
               NULL, wl->wl_ev_group, "journal write finished async");
           evcnt_attach_dynamic(&wl->wl_ev_metawrite, EVCNT_TYPE_MISC,
               NULL, wl->wl_ev_group, "metadata async write");
           evcnt_attach_dynamic(&wl->wl_ev_cacheflush, EVCNT_TYPE_MISC,
               NULL, wl->wl_ev_group, "cache flush");
   }
   
   static void
   wapbl_evcnt_free(struct wapbl *wl)
   {
           evcnt_detach(&wl->wl_ev_commit);
           evcnt_detach(&wl->wl_ev_journalwrite);
           evcnt_detach(&wl->wl_ev_jbufs_bio_nowait);
           evcnt_detach(&wl->wl_ev_metawrite);
           evcnt_detach(&wl->wl_ev_cacheflush);
   }
   
   static void
   wapbl_dkcache_init(struct wapbl *wl)
   {
           int error;
   
           /* Get disk cache flags */
           error = VOP_IOCTL(wl->wl_devvp, DIOCGCACHE, &wl->wl_dkcache,
               FWRITE, FSCRED);
           if (error) {
                   /* behave as if there was a write cache */
                   wl->wl_dkcache = DKCACHE_WRITE;
           }
   
           /* Use FUA instead of cache flush if available */
           if (ISSET(wl->wl_dkcache, DKCACHE_FUA))
                   wl->wl_jwrite_flags |= B_MEDIA_FUA;
   
           /* Use DPO for journal writes if available */
           if (ISSET(wl->wl_dkcache, DKCACHE_DPO))
                   wl->wl_jwrite_flags |= B_MEDIA_DPO;
   }
   
   static int
   wapbl_start_flush_inodes(struct wapbl *wl, struct wapbl_replay *wr)
   {
           int error, i;
   
           WAPBL_PRINTF(WAPBL_PRINT_REPLAY,
               ("wapbl_start: reusing log with %d inodes\n", wr->wr_inodescnt));
   
           /*
            * Its only valid to reuse the replay log if its
            * the same as the new log we just opened.
            */
           KDASSERT(!wapbl_replay_isopen(wr));
           KASSERT(wl->wl_devvp->v_type == VBLK);
           KASSERT(wr->wr_devvp->v_type == VBLK);
           KASSERT(wl->wl_devvp->v_rdev == wr->wr_devvp->v_rdev);
           KASSERT(wl->wl_logpbn == wr->wr_logpbn);
           KASSERT(wl->wl_circ_size == wr->wr_circ_size);
           KASSERT(wl->wl_circ_off == wr->wr_circ_off);
           KASSERT(wl->wl_log_dev_bshift == wr->wr_log_dev_bshift);
           KASSERT(wl->wl_fs_dev_bshift == wr->wr_fs_dev_bshift);
   
           wl->wl_wc_header->wc_generation = wr->wr_generation + 1;
   
           for (i = 0; i < wr->wr_inodescnt; i++)
                   wapbl_register_inode(wl, wr->wr_inodes[i].wr_inumber,
                       wr->wr_inodes[i].wr_imode);
   
           /* Make sure new transaction won't overwrite old inodes list */
           KDASSERT(wapbl_transaction_len(wl) <=
               wapbl_space_free(wl->wl_circ_size, wr->wr_inodeshead,
               wr->wr_inodestail));
   
           wl->wl_head = wl->wl_tail = wr->wr_inodeshead;
           wl->wl_reclaimable_bytes = wl->wl_reserved_bytes =
               wapbl_transaction_len(wl);
   
           error = wapbl_write_inodes(wl, &wl->wl_head);
           if (error)
                   return error;
   
           KASSERT(wl->wl_head != wl->wl_tail);
           KASSERT(wl->wl_head != 0);
   
           return 0;
   }
   
   int
   wapbl_start(struct wapbl ** wlp, struct mount *mp, struct vnode *vp,
           daddr_t off, size_t count, size_t blksize, struct wapbl_replay *wr,
           wapbl_flush_fn_t flushfn, wapbl_flush_fn_t flushabortfn)
   {
           struct wapbl *wl;
           struct vnode *devvp;
           daddr_t logpbn;
           int error;
           int log_dev_bshift = ilog2(blksize);
           int fs_dev_bshift = log_dev_bshift;
           int run;
   
           WAPBL_PRINTF(WAPBL_PRINT_OPEN, ("wapbl_start: vp=%p off=%" PRId64
               " count=%zu blksize=%zu\n", vp, off, count, blksize));
   
           if (log_dev_bshift > fs_dev_bshift) {
                   WAPBL_PRINTF(WAPBL_PRINT_OPEN,
                           ("wapbl: log device's block size cannot be larger "
                            "than filesystem's\n"));
                   /*
                    * Not currently implemented, although it could be if
                    * needed someday.
                    */
                   return ENOSYS;
           }
   
           if (off < 0)
                   return EINVAL;
   
           if (blksize < DEV_BSIZE)
                   return EINVAL;
           if (blksize % DEV_BSIZE)
                   return EINVAL;
   
           /* XXXTODO: verify that the full load is writable */
   
           /*
            * XXX check for minimum log size
            * minimum is governed by minimum amount of space
            * to complete a transaction. (probably truncate)
            */
           /* XXX for now pick something minimal */
           if ((count * blksize) < MAXPHYS) {
                   return ENOSPC;
           }
   
           if ((error = VOP_BMAP(vp, off, &devvp, &logpbn, &run)) != 0) {
                   return error;
           }
   
           wl = wapbl_calloc(1, sizeof(*wl));
           rw_init(&wl->wl_rwlock);
           mutex_init(&wl->wl_mtx, MUTEX_DEFAULT, IPL_NONE);
           cv_init(&wl->wl_reclaimable_cv, "wapblrec");
           TAILQ_INIT(&wl->wl_bufs);
           SIMPLEQ_INIT(&wl->wl_entries);
   
           wl->wl_logvp = vp;
           wl->wl_devvp = devvp;
           wl->wl_mount = mp;
           wl->wl_logpbn = logpbn;
           wl->wl_log_dev_bshift = log_dev_bshift;
           wl->wl_fs_dev_bshift = fs_dev_bshift;
   
           wl->wl_flush = flushfn;
           wl->wl_flush_abort = flushabortfn;
   
           /* Reserve two log device blocks for the commit headers */
           wl->wl_circ_off = 2<<wl->wl_log_dev_bshift;
           wl->wl_circ_size = ((count * blksize) - wl->wl_circ_off);
           /* truncate the log usage to a multiple of log_dev_bshift */
           wl->wl_circ_size >>= wl->wl_log_dev_bshift;
           wl->wl_circ_size <<= wl->wl_log_dev_bshift;
   
           /*
            * wl_bufbytes_max limits the size of the in memory transaction space.
            * - Since buffers are allocated and accounted for in units of
            *   PAGE_SIZE it is required to be a multiple of PAGE_SIZE
            *   (i.e. 1<<PAGE_SHIFT)
            * - Since the log device has to be written in units of
            *   1<<wl_log_dev_bshift it is required to be a multiple of
            *   1<<wl_log_dev_bshift.
            * - Since filesystem will provide data in units of 1<<wl_fs_dev_bshift,
            *   it is convenient to be a multiple of 1<<wl_fs_dev_bshift.
            * Therefore it must be multiple of the least common multiple of those
            * three quantities.  Fortunately, all of those quantities are
            * guaranteed to be a power of two, and the least common multiple of
            * a set of numbers which are all powers of two is simply the maximum
            * of those numbers.  Finally, the maximum logarithm of a power of two
            * is the same as the log of the maximum power of two.  So we can do
            * the following operations to size wl_bufbytes_max:
            */
   
           /* XXX fix actual number of pages reserved per filesystem. */
           wl->wl_bufbytes_max = MIN(wl->wl_circ_size, buf_memcalc() / 2);
   
           /* Round wl_bufbytes_max to the largest power of two constraint */
           wl->wl_bufbytes_max >>= PAGE_SHIFT;
           wl->wl_bufbytes_max <<= PAGE_SHIFT;
           wl->wl_bufbytes_max >>= wl->wl_log_dev_bshift;
           wl->wl_bufbytes_max <<= wl->wl_log_dev_bshift;
           wl->wl_bufbytes_max >>= wl->wl_fs_dev_bshift;
           wl->wl_bufbytes_max <<= wl->wl_fs_dev_bshift;
   
           /* XXX maybe use filesystem fragment size instead of 1024 */
           /* XXX fix actual number of buffers reserved per filesystem. */
           wl->wl_bufcount_max = (buf_nbuf() / 2) * 1024;
   
           wl->wl_brperjblock = ((1<<wl->wl_log_dev_bshift)
               - offsetof(struct wapbl_wc_blocklist, wc_blocks)) /
               sizeof(((struct wapbl_wc_blocklist *)0)->wc_blocks[0]);
           KASSERT(wl->wl_brperjblock > 0);
   
           /* XXX tie this into resource estimation */
           wl->wl_dealloclim = wl->wl_bufbytes_max / mp->mnt_stat.f_bsize / 2;
           TAILQ_INIT(&wl->wl_dealloclist);
   
           wapbl_inodetrk_init(wl, WAPBL_INODETRK_SIZE);
   
           wapbl_evcnt_init(wl);
   
           wapbl_dkcache_init(wl);
   
           /* Initialize the commit header */
           {
                   struct wapbl_wc_header *wc;
                   size_t len = 1 << wl->wl_log_dev_bshift;
                   wc = wapbl_calloc(1, len);
                   wc->wc_type = WAPBL_WC_HEADER;
                   wc->wc_len = len;
                   wc->wc_circ_off = wl->wl_circ_off;
                   wc->wc_circ_size = wl->wl_circ_size;
                   /* XXX wc->wc_fsid */
                   wc->wc_log_dev_bshift = wl->wl_log_dev_bshift;
                   wc->wc_fs_dev_bshift = wl->wl_fs_dev_bshift;
                   wl->wl_wc_header = wc;
                   wl->wl_wc_scratch = wapbl_alloc(len);
           }
   
           TAILQ_INIT(&wl->wl_iobufs);
           TAILQ_INIT(&wl->wl_iobufs_busy);
           for (int i = 0; i < wapbl_journal_iobufs; i++) {
                   struct buf *bp;
   
                   if ((bp = geteblk(MAXPHYS)) == NULL)
                           goto errout;
   
                   mutex_enter(&bufcache_lock);
                   mutex_enter(devvp->v_interlock);
                   bgetvp(devvp, bp);
                   mutex_exit(devvp->v_interlock);
                   mutex_exit(&bufcache_lock);
   
                   bp->b_dev = devvp->v_rdev;
   
                   TAILQ_INSERT_TAIL(&wl->wl_iobufs, bp, b_wapbllist);
           }
   
           /*
            * if there was an existing set of unlinked but
            * allocated inodes, preserve it in the new
            * log.
            */
           if (wr && wr->wr_inodescnt) {
                   error = wapbl_start_flush_inodes(wl, wr);
                   if (error)
                           goto errout;
           }
   
           error = wapbl_write_commit(wl, wl->wl_head, wl->wl_tail);
           if (error) {
                   goto errout;
           }
   
           *wlp = wl;
   #if defined(WAPBL_DEBUG)
           wapbl_debug_wl = wl;
   #endif
   
           return 0;
    errout:
           wapbl_discard(wl);
           wapbl_free(wl->wl_wc_scratch, wl->wl_wc_header->wc_len);
           wapbl_free(wl->wl_wc_header, wl->wl_wc_header->wc_len);
           while (!TAILQ_EMPTY(&wl->wl_iobufs)) {
                   struct buf *bp;
   
                   bp = TAILQ_FIRST(&wl->wl_iobufs);
                   TAILQ_REMOVE(&wl->wl_iobufs, bp, b_wapbllist);
                   brelse(bp, BC_INVAL);
           }
           wapbl_inodetrk_free(wl);
           wapbl_free(wl, sizeof(*wl));
   
           return error;
   }
   
   /*
    * Like wapbl_flush, only discards the transaction
    * completely
    */
   
   void
   wapbl_discard(struct wapbl *wl)
   {
           struct wapbl_entry *we;
           struct wapbl_dealloc *wd;
           struct buf *bp;
           int i;
   
           /*
            * XXX we may consider using upgrade here
            * if we want to call flush from inside a transaction
            */
           rw_enter(&wl->wl_rwlock, RW_WRITER);
           wl->wl_flush(wl->wl_mount, TAILQ_FIRST(&wl->wl_dealloclist));
   
   #ifdef WAPBL_DEBUG_PRINT
           {
                   pid_t pid = -1;
                   lwpid_t lid = -1;
                   if (curproc)
                           pid = curproc->p_pid;
                   if (curlwp)
                           lid = curlwp->l_lid;
   #ifdef WAPBL_DEBUG_BUFBYTES
                   WAPBL_PRINTF(WAPBL_PRINT_DISCARD,
                       ("wapbl_discard: thread %d.%d discarding "
                       "transaction\n"
                       "\tbufcount=%zu bufbytes=%zu bcount=%zu "
                       "deallocs=%d inodes=%d\n"
                       "\terrcnt = %u, reclaimable=%zu reserved=%zu "
                       "unsynced=%zu\n",
                       pid, lid, wl->wl_bufcount, wl->wl_bufbytes,
                       wl->wl_bcount, wl->wl_dealloccnt,
                       wl->wl_inohashcnt, wl->wl_error_count,
                       wl->wl_reclaimable_bytes, wl->wl_reserved_bytes,
                       wl->wl_unsynced_bufbytes));
                   SIMPLEQ_FOREACH(we, &wl->wl_entries, we_entries) {
                           WAPBL_PRINTF(WAPBL_PRINT_DISCARD,
                               ("\tentry: bufcount = %zu, reclaimable = %zu, "
                                "error = %d, unsynced = %zu\n",
                                we->we_bufcount, we->we_reclaimable_bytes,
                                we->we_error, we->we_unsynced_bufbytes));
                   }
   #else /* !WAPBL_DEBUG_BUFBYTES */
                   WAPBL_PRINTF(WAPBL_PRINT_DISCARD,
                       ("wapbl_discard: thread %d.%d discarding transaction\n"
                       "\tbufcount=%zu bufbytes=%zu bcount=%zu "
                       "deallocs=%d inodes=%d\n"
                       "\terrcnt = %u, reclaimable=%zu reserved=%zu\n",
                       pid, lid, wl->wl_bufcount, wl->wl_bufbytes,
                       wl->wl_bcount, wl->wl_dealloccnt,
                       wl->wl_inohashcnt, wl->wl_error_count,
                       wl->wl_reclaimable_bytes, wl->wl_reserved_bytes));
                   SIMPLEQ_FOREACH(we, &wl->wl_entries, we_entries) {
                           WAPBL_PRINTF(WAPBL_PRINT_DISCARD,
                               ("\tentry: bufcount = %zu, reclaimable = %zu, "
                                "error = %d\n",
                                we->we_bufcount, we->we_reclaimable_bytes,
                                we->we_error));
                   }
   #endif /* !WAPBL_DEBUG_BUFBYTES */
           }
   #endif /* WAPBL_DEBUG_PRINT */
   
           for (i = 0; i <= wl->wl_inohashmask; i++) {
                   struct wapbl_ino_head *wih;
                   struct wapbl_ino *wi;
   
                   wih = &wl->wl_inohash[i];
                   while ((wi = LIST_FIRST(wih)) != NULL) {
                           LIST_REMOVE(wi, wi_hash);
                           pool_put(&wapbl_ino_pool, wi);
                           KASSERT(wl->wl_inohashcnt > 0);
                           wl->wl_inohashcnt--;
                   }
           }
   
           /*
            * clean buffer list
            */
           mutex_enter(&bufcache_lock);
           mutex_enter(&wl->wl_mtx);
           while ((bp = TAILQ_FIRST(&wl->wl_bufs)) != NULL) {
                   if (bbusy(bp, 0, 0, &wl->wl_mtx) == 0) {
                           KASSERT(bp->b_flags & B_LOCKED);
                           KASSERT(bp->b_oflags & BO_DELWRI);
                           /*
                            * Buffer is already on BQ_LOCKED queue.
                            * The buffer will be unlocked and
                            * removed from the transaction in brelsel()
                            */
                           mutex_exit(&wl->wl_mtx);
                           bremfree(bp);
                           brelsel(bp, BC_INVAL);
                           mutex_enter(&wl->wl_mtx);
                   }
           }
   
           /*
            * Remove references to this wl from wl_entries, free any which
            * no longer have buffers, others will be freed in wapbl_biodone()
            * when they no longer have any buffers.
            */
           while ((we = SIMPLEQ_FIRST(&wl->wl_entries)) != NULL) {
                   SIMPLEQ_REMOVE_HEAD(&wl->wl_entries, we_entries);
                   /* XXX should we be accumulating wl_error_count
                    * and increasing reclaimable bytes ? */
                   we->we_wapbl = NULL;
                   if (we->we_bufcount == 0) {
   #ifdef WAPBL_DEBUG_BUFBYTES
                           KASSERT(we->we_unsynced_bufbytes == 0);
   #endif
                           pool_put(&wapbl_entry_pool, we);
                   }
           }
   
           mutex_exit(&wl->wl_mtx);
           mutex_exit(&bufcache_lock);
   
           /* Discard list of deallocs */
           while ((wd = TAILQ_FIRST(&wl->wl_dealloclist)) != NULL)
                   wapbl_deallocation_free(wl, wd, true);
   
           /* XXX should we clear wl_reserved_bytes? */
   
           KASSERT(wl->wl_bufbytes == 0);
           KASSERT(wl->wl_bcount == 0);
           KASSERT(wl->wl_bufcount == 0);
           KASSERT(TAILQ_EMPTY(&wl->wl_bufs));
           KASSERT(SIMPLEQ_EMPTY(&wl->wl_entries));
           KASSERT(wl->wl_inohashcnt == 0);
           KASSERT(TAILQ_EMPTY(&wl->wl_dealloclist));
           KASSERT(wl->wl_dealloccnt == 0);
   
           rw_exit(&wl->wl_rwlock);
   }
   
   int
   wapbl_stop(struct wapbl *wl, int force)
   {
           int error;
   
           WAPBL_PRINTF(WAPBL_PRINT_OPEN, ("wapbl_stop called\n"));
           error = wapbl_flush(wl, 1);
           if (error) {
                   if (force)
                           wapbl_discard(wl);
                   else
                           return error;
           }
   
           /* Unlinked inodes persist after a flush */
           if (wl->wl_inohashcnt) {
                   if (force) {
                           wapbl_discard(wl);
                   } else {
                           return EBUSY;
                   }
           }
   
           KASSERT(wl->wl_bufbytes == 0);
           KASSERT(wl->wl_bcount == 0);
           KASSERT(wl->wl_bufcount == 0);
           KASSERT(TAILQ_EMPTY(&wl->wl_bufs));
           KASSERT(wl->wl_dealloccnt == 0);
           KASSERT(SIMPLEQ_EMPTY(&wl->wl_entries));
           KASSERT(wl->wl_inohashcnt == 0);
           KASSERT(TAILQ_EMPTY(&wl->wl_dealloclist));
           KASSERT(wl->wl_dealloccnt == 0);
           KASSERT(TAILQ_EMPTY(&wl->wl_iobufs_busy));
   
           wapbl_free(wl->wl_wc_scratch, wl->wl_wc_header->wc_len);
           wapbl_free(wl->wl_wc_header, wl->wl_wc_header->wc_len);
           while (!TAILQ_EMPTY(&wl->wl_iobufs)) {
                   struct buf *bp;
   
                   bp = TAILQ_FIRST(&wl->wl_iobufs);
                   TAILQ_REMOVE(&wl->wl_iobufs, bp, b_wapbllist);
                   brelse(bp, BC_INVAL);
           }
           wapbl_inodetrk_free(wl);
   
           wapbl_evcnt_free(wl);
   
           cv_destroy(&wl->wl_reclaimable_cv);
           mutex_destroy(&wl->wl_mtx);
           rw_destroy(&wl->wl_rwlock);
           wapbl_free(wl, sizeof(*wl));
   
           return 0;
   }
   
   /****************************************************************/
   /*
    * Unbuffered disk I/O
    */
   
   static void
   wapbl_doio_accounting(struct vnode *devvp, int flags)
   {
           struct pstats *pstats = curlwp->l_proc->p_stats;
   
           if ((flags & (B_WRITE | B_READ)) == B_WRITE) {
                   mutex_enter(devvp->v_interlock);
                   devvp->v_numoutput++;
                   mutex_exit(devvp->v_interlock);
                   pstats->p_ru.ru_oublock++;
           } else {
                   pstats->p_ru.ru_inblock++;
           }
   
   }
   
   static int
   wapbl_doio(void *data, size_t len, struct vnode *devvp, daddr_t pbn, int flags)
   {
           struct buf *bp;
           int error;
   
           KASSERT(devvp->v_type == VBLK);
   
           wapbl_doio_accounting(devvp, flags);
   
           bp = getiobuf(devvp, true);
           bp->b_flags = flags;
           bp->b_cflags |= BC_BUSY;        /* mandatory, asserted by biowait() */
           bp->b_dev = devvp->v_rdev;
           bp->b_data = data;
           bp->b_bufsize = bp->b_resid = bp->b_bcount = len;
           bp->b_blkno = pbn;
           BIO_SETPRIO(bp, BPRIO_TIMECRITICAL);
   
           WAPBL_PRINTF(WAPBL_PRINT_IO,
               ("wapbl_doio: %s %d bytes at block %"PRId64" on dev 0x%"PRIx64"\n",
               BUF_ISWRITE(bp) ? "write" : "read", bp->b_bcount,
               bp->b_blkno, bp->b_dev));
   
           VOP_STRATEGY(devvp, bp);
   
           error = biowait(bp);
           putiobuf(bp);
   
           if (error) {
                   WAPBL_PRINTF(WAPBL_PRINT_ERROR,
                       ("wapbl_doio: %s %zu bytes at block %" PRId64
                       " on dev 0x%"PRIx64" failed with error %d\n",
                       (((flags & (B_WRITE | B_READ)) == B_WRITE) ?
                        "write" : "read"),
                       len, pbn, devvp->v_rdev, error));
           }
   
           return error;
   }
   
   /*
    * wapbl_write(data, len, devvp, pbn)
    *
    *      Synchronously write len bytes from data to physical block pbn
    *      on devvp.
    */
   int
   wapbl_write(void *data, size_t len, struct vnode *devvp, daddr_t pbn)
   {
   
           return wapbl_doio(data, len, devvp, pbn, B_WRITE);
   }
   
   /*
    * wapbl_read(data, len, devvp, pbn)
    *
    *      Synchronously read len bytes into data from physical block pbn
    *      on devvp.
    */
   int
   wapbl_read(void *data, size_t len, struct vnode *devvp, daddr_t pbn)
   {
   
           return wapbl_doio(data, len, devvp, pbn, B_READ);
   }
   
   /****************************************************************/
   /*
    * Buffered disk writes -- try to coalesce writes and emit
    * MAXPHYS-aligned blocks.
    */
   
   /*
    * wapbl_buffered_write_async(wl, bp)
    *
    *      Send buffer for asynchronous write.
    */
   static void
   wapbl_buffered_write_async(struct wapbl *wl, struct buf *bp)
   {
           wapbl_doio_accounting(wl->wl_devvp, bp->b_flags);
   
           KASSERT(TAILQ_FIRST(&wl->wl_iobufs) == bp);
           TAILQ_REMOVE(&wl->wl_iobufs, bp, b_wapbllist);
   
           bp->b_flags |= B_WRITE;
           bp->b_cflags |= BC_BUSY;        /* mandatory, asserted by biowait() */
           bp->b_oflags = 0;
           bp->b_bcount = bp->b_resid;
           BIO_SETPRIO(bp, BPRIO_TIMECRITICAL);
  
          VOP_STRATEGY(wl->wl_devvp, bp);
  
          wl->wl_ev_journalwrite.ev_count++;
  
          TAILQ_INSERT_TAIL(&wl->wl_iobufs_busy, bp, b_wapbllist);
  }
  
  /*
   * wapbl_buffered_flush(wl)
   *
   *      Flush any buffered writes from wapbl_buffered_write.
   */
  static int
  wapbl_buffered_flush(struct wapbl *wl, bool full)
  {
          int error = 0;
          struct buf *bp, *bnext;
          bool only_done = true, found = false;
  
          /* if there is outstanding buffered write, send it now */
          if ((bp = TAILQ_FIRST(&wl->wl_iobufs)) && bp->b_resid > 0)
                  wapbl_buffered_write_async(wl, bp);
  
          /* wait for I/O to complete */
  again:
          TAILQ_FOREACH_SAFE(bp, &wl->wl_iobufs_busy, b_wapbllist, bnext) {
                  if (!full && only_done) {
                          /* skip unfinished */
                          if (!ISSET(bp->b_oflags, BO_DONE))
                                  continue;
                  }
                          
                  if (ISSET(bp->b_oflags, BO_DONE))
                          wl->wl_ev_jbufs_bio_nowait.ev_count++;
  
                  TAILQ_REMOVE(&wl->wl_iobufs_busy, bp, b_wapbllist);
                  error = biowait(bp);
  
                  /* reset for reuse */
                  bp->b_blkno = bp->b_resid = bp->b_flags = 0;
                  TAILQ_INSERT_TAIL(&wl->wl_iobufs, bp, b_wapbllist);
                  found = true;
  
                  if (!full)
                          break;
          }
  
          if (!found && only_done && !TAILQ_EMPTY(&wl->wl_iobufs_busy)) {
                  only_done = false;
                  goto again;
          }
  
          return error;
  }
  
  /*
   * wapbl_buffered_write(data, len, wl, pbn)
   *
   *      Write len bytes from data to physical block pbn on
   *      wl->wl_devvp.  The write may not complete until
   *      wapbl_buffered_flush.
   */
  static int
  wapbl_buffered_write(void *data, size_t len, struct wapbl *wl, daddr_t pbn,
      int bflags)
  {
          size_t resid;
          struct buf *bp;
  
  again:
          bp = TAILQ_FIRST(&wl->wl_iobufs);
  
          if (bp == NULL) {
                  /* No more buffers, wait for any previous I/O to finish. */
                  wapbl_buffered_flush(wl, false);
  
                  bp = TAILQ_FIRST(&wl->wl_iobufs);
                  KASSERT(bp != NULL);
          }
  
          /*
           * If not adjacent to buffered data flush first.  Disk block
           * address is always valid for non-empty buffer.
           */
          if ((bp->b_resid > 0 && pbn != bp->b_blkno + btodb(bp->b_resid))) {
                  wapbl_buffered_write_async(wl, bp);
                  goto again;
          }
  
          /*
           * If this write goes to an empty buffer we have to
           * save the disk block address first.
           */
          if (bp->b_blkno == 0) {
                  bp->b_blkno = pbn;
                  bp->b_flags |= bflags;
          }
  
          /*
           * Remaining space so this buffer ends on a buffer size boundary.
           *
           * Cannot become less or equal zero as the buffer would have been
           * flushed on the last call then.
           */
          resid = bp->b_bufsize - dbtob(bp->b_blkno % btodb(bp->b_bufsize)) -
              bp->b_resid;
          KASSERT(resid > 0);
          KASSERT(dbtob(btodb(resid)) == resid);
  
          if (len < resid)
                  resid = len;
  
          memcpy((uint8_t *)bp->b_data + bp->b_resid, data, resid);
          bp->b_resid += resid;
  
          if (len >= resid) {
                  /* Just filled the buf, or data did not fit */
                  wapbl_buffered_write_async(wl, bp);
  
                  data = (uint8_t *)data + resid;
                  len -= resid;
                  pbn += btodb(resid);
  
                  if (len > 0)
                          goto again;
          }
  
          return 0;
  }
  
  /*
   * wapbl_circ_write(wl, data, len, offp)
   *
   *      Write len bytes from data to the circular queue of wl, starting
   *      at linear byte offset *offp, and returning the new linear byte
   *      offset in *offp.
   *
   *      If the starting linear byte offset precedes wl->wl_circ_off,
   *      the write instead begins at wl->wl_circ_off.  XXX WTF?  This
   *      should be a KASSERT, not a conditional.
   *
   *      The write is buffered in wl and must be flushed with
   *      wapbl_buffered_flush before it will be submitted to the disk.
   */
  static int
  wapbl_circ_write(struct wapbl *wl, void *data, size_t len, off_t *offp)
  {
          size_t slen;
          off_t off = *offp;
          int error;
          daddr_t pbn;
  
          KDASSERT(((len >> wl->wl_log_dev_bshift) <<
              wl->wl_log_dev_bshift) == len);
  
          if (off < wl->wl_circ_off)
                  off = wl->wl_circ_off;
          slen = wl->wl_circ_off + wl->wl_circ_size - off;
          if (slen < len) {
                  pbn = wl->wl_logpbn + (off >> wl->wl_log_dev_bshift);
  #ifdef _KERNEL
                  pbn = btodb(pbn << wl->wl_log_dev_bshift);
  #endif
                  error = wapbl_buffered_write(data, slen, wl, pbn,
                      WAPBL_JDATA_FLAGS(wl));
                  if (error)
                          return error;
                  data = (uint8_t *)data + slen;
                  len -= slen;
                  off = wl->wl_circ_off;
          }
          pbn = wl->wl_logpbn + (off >> wl->wl_log_dev_bshift);
  #ifdef _KERNEL
          pbn = btodb(pbn << wl->wl_log_dev_bshift);
  #endif
          error = wapbl_buffered_write(data, len, wl, pbn,
              WAPBL_JDATA_FLAGS(wl));
          if (error)
                  return error;
          off += len;
          if (off >= wl->wl_circ_off + wl->wl_circ_size)
                  off = wl->wl_circ_off;
          *offp = off;
          return 0;
  }
  
  /****************************************************************/
  /*
   * WAPBL transactions: entering, adding/removing bufs, and exiting
   */
  
  int
  wapbl_begin(struct wapbl *wl, const char *file, int line)
  {
          int doflush;
          unsigned lockcount;
  
          KDASSERT(wl);
  
          /*
           * XXX this needs to be made much more sophisticated.
           * perhaps each wapbl_begin could reserve a specified
           * number of buffers and bytes.
           */
          mutex_enter(&wl->wl_mtx);
          lockcount = wl->wl_lock_count;
          doflush = ((wl->wl_bufbytes + (lockcount * MAXPHYS)) >
                     wl->wl_bufbytes_max / 2) ||
                    ((wl->wl_bufcount + (lockcount * 10)) >
                     wl->wl_bufcount_max / 2) ||
                    (wapbl_transaction_len(wl) > wl->wl_circ_size / 2) ||
                    (wl->wl_dealloccnt >= (wl->wl_dealloclim / 2));
          mutex_exit(&wl->wl_mtx);
  
          if (doflush) {
                  WAPBL_PRINTF(WAPBL_PRINT_FLUSH,
                      ("force flush lockcnt=%d bufbytes=%zu "
                      "(max=%zu) bufcount=%zu (max=%zu) "
                      "dealloccnt %d (lim=%d)\n",
                      lockcount, wl->wl_bufbytes,
                      wl->wl_bufbytes_max, wl->wl_bufcount,
                      wl->wl_bufcount_max,
                      wl->wl_dealloccnt, wl->wl_dealloclim));
          }
  
          if (doflush) {
                  int error = wapbl_flush(wl, 0);
                  if (error)
                          return error;
          }
  
          rw_enter(&wl->wl_rwlock, RW_READER);
          mutex_enter(&wl->wl_mtx);
          wl->wl_lock_count++;
          mutex_exit(&wl->wl_mtx);
  
  #if defined(WAPBL_DEBUG_PRINT)
          WAPBL_PRINTF(WAPBL_PRINT_TRANSACTION,
              ("wapbl_begin thread %d.%d with bufcount=%zu "
              "bufbytes=%zu bcount=%zu at %s:%d\n",
              curproc->p_pid, curlwp->l_lid, wl->wl_bufcount,
              wl->wl_bufbytes, wl->wl_bcount, file, line));
  #endif
  
          return 0;
  }
  
  void
  wapbl_end(struct wapbl *wl)
  {
  
  #if defined(WAPBL_DEBUG_PRINT)
          WAPBL_PRINTF(WAPBL_PRINT_TRANSACTION,
               ("wapbl_end thread %d.%d with bufcount=%zu "
                "bufbytes=%zu bcount=%zu\n",
                curproc->p_pid, curlwp->l_lid, wl->wl_bufcount,
                wl->wl_bufbytes, wl->wl_bcount));
  #endif
  
          /*
           * XXX this could be handled more gracefully, perhaps place
           * only a partial transaction in the log and allow the
           * remaining to flush without the protection of the journal.
           */
          KASSERTMSG((wapbl_transaction_len(wl) <=
                  (wl->wl_circ_size - wl->wl_reserved_bytes)),
              "wapbl_end: current transaction too big to flush");
  
          mutex_enter(&wl->wl_mtx);
          KASSERT(wl->wl_lock_count > 0);
          wl->wl_lock_count--;
          mutex_exit(&wl->wl_mtx);
  
          rw_exit(&wl->wl_rwlock);
  }
  
  void
  wapbl_add_buf(struct wapbl *wl, struct buf * bp)
  {
  
          KASSERT(bp->b_cflags & BC_BUSY);
          KASSERT(bp->b_vp);
  
          wapbl_jlock_assert(wl);
  
  #if 0
          /*
           * XXX this might be an issue for swapfiles.
           * see uvm_swap.c:1702
           *
           * XXX2 why require it then?  leap of semantics?
           */
          KASSERT((bp->b_cflags & BC_NOCACHE) == 0);
  #endif
  
          mutex_enter(&wl->wl_mtx);
          if (bp->b_flags & B_LOCKED) {
                  TAILQ_REMOVE(&wl->wl_bufs, bp, b_wapbllist);
                  WAPBL_PRINTF(WAPBL_PRINT_BUFFER2,
                     ("wapbl_add_buf thread %d.%d re-adding buf %p "
                      "with %d bytes %d bcount\n",
                      curproc->p_pid, curlwp->l_lid, bp, bp->b_bufsize,
                      bp->b_bcount));
          } else {
                  /* unlocked by dirty buffers shouldn't exist */
                  KASSERT(!(bp->b_oflags & BO_DELWRI));
                  wl->wl_bufbytes += bp->b_bufsize;
                  wl->wl_bcount += bp->b_bcount;
                  wl->wl_bufcount++;
                  WAPBL_PRINTF(WAPBL_PRINT_BUFFER,
                     ("wapbl_add_buf thread %d.%d adding buf %p "
                      "with %d bytes %d bcount\n",
                      curproc->p_pid, curlwp->l_lid, bp, bp->b_bufsize,
                      bp->b_bcount));
          }
          TAILQ_INSERT_TAIL(&wl->wl_bufs, bp, b_wapbllist);
          mutex_exit(&wl->wl_mtx);
  
          bp->b_flags |= B_LOCKED;
  }
  
  static void
  wapbl_remove_buf_locked(struct wapbl * wl, struct buf *bp)
  {
  
          KASSERT(mutex_owned(&wl->wl_mtx));
          KASSERT(bp->b_cflags & BC_BUSY);
          wapbl_jlock_assert(wl);
  
  #if 0
          /*
           * XXX this might be an issue for swapfiles.
           * see uvm_swap.c:1725
           *
           * XXXdeux: see above
           */
          KASSERT((bp->b_flags & BC_NOCACHE) == 0);
  #endif
          KASSERT(bp->b_flags & B_LOCKED);
  
          WAPBL_PRINTF(WAPBL_PRINT_BUFFER,
             ("wapbl_remove_buf thread %d.%d removing buf %p with "
              "%d bytes %d bcount\n",
              curproc->p_pid, curlwp->l_lid, bp, bp->b_bufsize, bp->b_bcount));
  
          KASSERT(wl->wl_bufbytes >= bp->b_bufsize);
          wl->wl_bufbytes -= bp->b_bufsize;
          KASSERT(wl->wl_bcount >= bp->b_bcount);
          wl->wl_bcount -= bp->b_bcount;
          KASSERT(wl->wl_bufcount > 0);
          wl->wl_bufcount--;
          KASSERT((wl->wl_bufcount == 0) == (wl->wl_bufbytes == 0));
          KASSERT((wl->wl_bufcount == 0) == (wl->wl_bcount == 0));
          TAILQ_REMOVE(&wl->wl_bufs, bp, b_wapbllist);
  
          bp->b_flags &= ~B_LOCKED;
  }
  
  /* called from brelsel() in vfs_bio among other places */
  void
  wapbl_remove_buf(struct wapbl * wl, struct buf *bp)
  {
  
          mutex_enter(&wl->wl_mtx);
          wapbl_remove_buf_locked(wl, bp);
          mutex_exit(&wl->wl_mtx);
  }
  
  void
  wapbl_resize_buf(struct wapbl *wl, struct buf *bp, long oldsz, long oldcnt)
  {
  
          KASSERT(bp->b_cflags & BC_BUSY);
  
          /*
           * XXX: why does this depend on B_LOCKED?  otherwise the buf
           * is not for a transaction?  if so, why is this called in the
           * first place?
           */
          if (bp->b_flags & B_LOCKED) {
                  mutex_enter(&wl->wl_mtx);
                  wl->wl_bufbytes += bp->b_bufsize - oldsz;
                  wl->wl_bcount += bp->b_bcount - oldcnt;
                  mutex_exit(&wl->wl_mtx);
          }
  }
  
  #endif /* _KERNEL */
  
  /****************************************************************/
  /* Some utility inlines */
  
  /*
   * wapbl_space_used(avail, head, tail)
   *
   *      Number of bytes used in a circular queue of avail total bytes,
   *      from tail to head.
   */
  static inline size_t
  wapbl_space_used(size_t avail, off_t head, off_t tail)
  {
  
          if (tail == 0) {
                  KASSERT(head == 0);
                  return 0;
          }
          return ((head + (avail - 1) - tail) % avail) + 1;
  }
  
  #ifdef _KERNEL
  /*
   * wapbl_advance(size, off, oldoff, delta)
   *
   *      Given a byte offset oldoff into a circular queue of size bytes
   *      starting at off, return a new byte offset oldoff + delta into
   *      the circular queue.
   */
  static inline off_t
  wapbl_advance(size_t size, size_t off, off_t oldoff, size_t delta)
  {
          off_t newoff;
  
          /* Define acceptable ranges for inputs. */
          KASSERT(delta <= (size_t)size);
          KASSERT((oldoff == 0) || ((size_t)oldoff >= off));
          KASSERT(oldoff < (off_t)(size + off));
  
          if ((oldoff == 0) && (delta != 0))
                  newoff = off + delta;
          else if ((oldoff + delta) < (size + off))
                  newoff = oldoff + delta;
          else
                  newoff = (oldoff + delta) - size;
  
          /* Note some interesting axioms */
          KASSERT((delta != 0) || (newoff == oldoff));
          KASSERT((delta == 0) || (newoff != 0));
          KASSERT((delta != (size)) || (newoff == oldoff));
  
          /* Define acceptable ranges for output. */
          KASSERT((newoff == 0) || ((size_t)newoff >= off));
          KASSERT((size_t)newoff < (size + off));
          return newoff;
  }
  
  /*
   * wapbl_space_free(avail, head, tail)
   *
   *      Number of bytes free in a circular queue of avail total bytes,
   *      in which everything from tail to head is used.
   */
  static inline size_t
  wapbl_space_free(size_t avail, off_t head, off_t tail)
  {
  
          return avail - wapbl_space_used(avail, head, tail);
  }
  
  /*
   * wapbl_advance_head(size, off, delta, headp, tailp)
   *
   *      In a circular queue of size bytes starting at off, given the
   *      old head and tail offsets *headp and *tailp, store the new head
   *      and tail offsets in *headp and *tailp resulting from adding
   *      delta bytes of data to the head.
   */
  static inline void
  wapbl_advance_head(size_t size, size_t off, size_t delta, off_t *headp,
                     off_t *tailp)
  {
          off_t head = *headp;
          off_t tail = *tailp;
  
          KASSERT(delta <= wapbl_space_free(size, head, tail));
          head = wapbl_advance(size, off, head, delta);
          if ((tail == 0) && (head != 0))
                  tail = off;
          *headp = head;
          *tailp = tail;
  }
  
  /*
   * wapbl_advance_tail(size, off, delta, headp, tailp)
   *
   *      In a circular queue of size bytes starting at off, given the
   *      old head and tail offsets *headp and *tailp, store the new head
   *      and tail offsets in *headp and *tailp resulting from removing
   *      delta bytes of data from the tail.
   */
  static inline void
  wapbl_advance_tail(size_t size, size_t off, size_t delta, off_t *headp,
                     off_t *tailp)
  {
          off_t head = *headp;
          off_t tail = *tailp;
  
          KASSERT(delta <= wapbl_space_used(size, head, tail));
          tail = wapbl_advance(size, off, tail, delta);
          if (head == tail) {
                  head = tail = 0;
          }
          *headp = head;
          *tailp = tail;
  }
  
  
  /****************************************************************/
  
  /*
   * wapbl_truncate(wl, minfree)
   *
   *      Wait until at least minfree bytes are available in the log.
   *
   *      If it was necessary to wait for writes to complete,
   *      advance the circular queue tail to reflect the new write
   *      completions and issue a write commit to the log.
   *
   *      => Caller must hold wl->wl_rwlock writer lock.
   */
  static int
  wapbl_truncate(struct wapbl *wl, size_t minfree)
  {
          size_t delta;
          size_t avail;
          off_t head;
          off_t tail;
          int error = 0;
  
          KASSERT(minfree <= (wl->wl_circ_size - wl->wl_reserved_bytes));
          KASSERT(rw_write_held(&wl->wl_rwlock));
  
          mutex_enter(&wl->wl_mtx);
  
          /*
           * First check to see if we have to do a commit
           * at all.
           */
          avail = wapbl_space_free(wl->wl_circ_size, wl->wl_head, wl->wl_tail);
          if (minfree < avail) {
                  mutex_exit(&wl->wl_mtx);
                  return 0;
          }
          minfree -= avail;
          while ((wl->wl_error_count == 0) &&
              (wl->wl_reclaimable_bytes < minfree)) {
                  WAPBL_PRINTF(WAPBL_PRINT_TRUNCATE,
                     ("wapbl_truncate: sleeping on %p wl=%p bytes=%zd "
                      "minfree=%zd\n",
                      &wl->wl_reclaimable_bytes, wl, wl->wl_reclaimable_bytes,
                      minfree));
  
                  cv_wait(&wl->wl_reclaimable_cv, &wl->wl_mtx);
          }
          if (wl->wl_reclaimable_bytes < minfree) {
                  KASSERT(wl->wl_error_count);
                  /* XXX maybe get actual error from buffer instead someday? */
                  error = EIO;
          }
          head = wl->wl_head;
          tail = wl->wl_tail;
          delta = wl->wl_reclaimable_bytes;
  
          /* If all of of the entries are flushed, then be sure to keep
           * the reserved bytes reserved.  Watch out for discarded transactions,
           * which could leave more bytes reserved than are reclaimable.
           */
          if (SIMPLEQ_EMPTY(&wl->wl_entries) &&
              (delta >= wl->wl_reserved_bytes)) {
                  delta -= wl->wl_reserved_bytes;
          }
          wapbl_advance_tail(wl->wl_circ_size, wl->wl_circ_off, delta, &head,
                             &tail);
          KDASSERT(wl->wl_reserved_bytes <=
                  wapbl_space_used(wl->wl_circ_size, head, tail));
          mutex_exit(&wl->wl_mtx);
  
          if (error)
                  return error;
  
          /*
           * This is where head, tail and delta are unprotected
           * from races against itself or flush.  This is ok since
           * we only call this routine from inside flush itself.
           *
           * XXX: how can it race against itself when accessed only
           * from behind the write-locked rwlock?
           */
          error = wapbl_write_commit(wl, head, tail);
          if (error)
                  return error;
  
          wl->wl_head = head;
          wl->wl_tail = tail;
  
          mutex_enter(&wl->wl_mtx);
          KASSERT(wl->wl_reclaimable_bytes >= delta);
          wl->wl_reclaimable_bytes -= delta;
          mutex_exit(&wl->wl_mtx);
          WAPBL_PRINTF(WAPBL_PRINT_TRUNCATE,
              ("wapbl_truncate thread %d.%d truncating %zu bytes\n",
              curproc->p_pid, curlwp->l_lid, delta));
  
          return 0;
  }
  
  /****************************************************************/
  
  void
  wapbl_biodone(struct buf *bp)
  {
          struct wapbl_entry *we = bp->b_private;
          struct wapbl *wl;
  #ifdef WAPBL_DEBUG_BUFBYTES
          const int bufsize = bp->b_bufsize;
  #endif
  
          mutex_enter(&bufcache_lock);
          wl = we->we_wapbl;
          mutex_exit(&bufcache_lock);
  
          /*
           * Handle possible flushing of buffers after log has been
           * decomissioned.
           */
          if (!wl) {
                  KASSERT(we->we_bufcount > 0);
                  we->we_bufcount--;
  #ifdef WAPBL_DEBUG_BUFBYTES
                  KASSERT(we->we_unsynced_bufbytes >= bufsize);
                  we->we_unsynced_bufbytes -= bufsize;
  #endif
  
                  if (we->we_bufcount == 0) {
  #ifdef WAPBL_DEBUG_BUFBYTES
                          KASSERT(we->we_unsynced_bufbytes == 0);
  #endif
                          pool_put(&wapbl_entry_pool, we);
                  }
  
                  brelse(bp, 0);
                  return;
          }
  
  #ifdef ohbother
          KDASSERT(bp->b_oflags & BO_DONE);
          KDASSERT(!(bp->b_oflags & BO_DELWRI));
          KDASSERT(bp->b_flags & B_ASYNC);
          KDASSERT(bp->b_cflags & BC_BUSY);
          KDASSERT(!(bp->b_flags & B_LOCKED));
          KDASSERT(!(bp->b_flags & B_READ));
          KDASSERT(!(bp->b_cflags & BC_INVAL));
          KDASSERT(!(bp->b_cflags & BC_NOCACHE));
  #endif
  
          if (bp->b_error) {
                  /*
                   * If an error occurs, it would be nice to leave the buffer
                   * as a delayed write on the LRU queue so that we can retry
                   * it later. But buffercache(9) can't handle dirty buffer
                   * reuse, so just mark the log permanently errored out.
                   */
                  mutex_enter(&wl->wl_mtx);
                  if (wl->wl_error_count == 0) {
                          wl->wl_error_count++;
                          cv_broadcast(&wl->wl_reclaimable_cv);
                  }
                  mutex_exit(&wl->wl_mtx);
          }
  
          /*
           * Make sure that the buf doesn't retain the media flags, so that
           * e.g. wapbl_allow_fuadpo has immediate effect on any following I/O.
           * The flags will be set again if needed by another I/O.
           */
          bp->b_flags &= ~B_MEDIA_FLAGS;
  
          /*
           * Release the buffer here. wapbl_flush() may wait for the
           * log to become empty and we better unbusy the buffer before
           * wapbl_flush() returns.
           */
          brelse(bp, 0);
  
          mutex_enter(&wl->wl_mtx);
  
          KASSERT(we->we_bufcount > 0);
          we->we_bufcount--;
  #ifdef WAPBL_DEBUG_BUFBYTES
          KASSERT(we->we_unsynced_bufbytes >= bufsize);
          we->we_unsynced_bufbytes -= bufsize;
          KASSERT(wl->wl_unsynced_bufbytes >= bufsize);
          wl->wl_unsynced_bufbytes -= bufsize;
  #endif
          wl->wl_ev_metawrite.ev_count++;
  
          /*
           * If the current transaction can be reclaimed, start
           * at the beginning and reclaim any consecutive reclaimable
           * transactions.  If we successfully reclaim anything,
           * then wakeup anyone waiting for the reclaim.
           */
          if (we->we_bufcount == 0) {
                  size_t delta = 0;
                  int errcnt = 0;
  #ifdef WAPBL_DEBUG_BUFBYTES
                  KDASSERT(we->we_unsynced_bufbytes == 0);
  #endif
                  /*
                   * clear any posted error, since the buffer it came from
                   * has successfully flushed by now
                   */
                  while ((we = SIMPLEQ_FIRST(&wl->wl_entries)) &&
                         (we->we_bufcount == 0)) {
                          delta += we->we_reclaimable_bytes;
                          if (we->we_error)
                                  errcnt++;
                          SIMPLEQ_REMOVE_HEAD(&wl->wl_entries, we_entries);
                          pool_put(&wapbl_entry_pool, we);
                  }
  
                  if (delta) {
                          wl->wl_reclaimable_bytes += delta;
                          KASSERT(wl->wl_error_count >= errcnt);
                          wl->wl_error_count -= errcnt;
                          cv_broadcast(&wl->wl_reclaimable_cv);
                  }
          }
  
          mutex_exit(&wl->wl_mtx);
  }
  
  /*
   * wapbl_flush(wl, wait)
   *
   *      Flush pending block writes, deallocations, and inodes from
   *      the current transaction in memory to the log on disk:
   *
   *      1. Call the file system's wl_flush callback to flush any
   *         per-file-system pending updates.
   *      2. Wait for enough space in the log for the current transaction.
   *      3. Synchronously write the new log records, advancing the
   *         circular queue head.
   *      4. Issue the pending block writes asynchronously, now that they
   *         are recorded in the log and can be replayed after crash.
   *      5. If wait is true, wait for all writes to complete and for the
   *         log to become empty.
   *
   *      On failure, call the file system's wl_flush_abort callback.
   */
  int
  wapbl_flush(struct wapbl *wl, int waitfor)
  {
          struct buf *bp;
          struct wapbl_entry *we;
          off_t off;
          off_t head;
          off_t tail;
          size_t delta = 0;
          size_t flushsize;
          size_t reserved;
          int error = 0;
  
          /*
           * Do a quick check to see if a full flush can be skipped
           * This assumes that the flush callback does not need to be called
           * unless there are other outstanding bufs.
           */
          if (!waitfor) {
                  size_t nbufs;
                  mutex_enter(&wl->wl_mtx);       /* XXX need mutex here to
                                                     protect the KASSERTS */
                  nbufs = wl->wl_bufcount;
                  KASSERT((wl->wl_bufcount == 0) == (wl->wl_bufbytes == 0));
                  KASSERT((wl->wl_bufcount == 0) == (wl->wl_bcount == 0));
                  mutex_exit(&wl->wl_mtx);
                  if (nbufs == 0)
                          return 0;
          }
  
          /*
           * XXX we may consider using LK_UPGRADE here
           * if we want to call flush from inside a transaction
           */
          rw_enter(&wl->wl_rwlock, RW_WRITER);
          wl->wl_flush(wl->wl_mount, TAILQ_FIRST(&wl->wl_dealloclist));
  
          /*
           * Now that we are exclusively locked and the file system has
           * issued any deferred block writes for this transaction, check
           * whether there are any blocks to write to the log.  If not,
           * skip waiting for space or writing any log entries.
           *
           * XXX Shouldn't this also check wl_dealloccnt and
           * wl_inohashcnt?  Perhaps wl_dealloccnt doesn't matter if the
           * file system didn't produce any blocks as a consequence of
           * it, but the same does not seem to be so of wl_inohashcnt.
           */
          if (wl->wl_bufcount == 0) {
                  goto wait_out;
          }
  
  #if 0
          WAPBL_PRINTF(WAPBL_PRINT_FLUSH,
                       ("wapbl_flush thread %d.%d flushing entries with "
                        "bufcount=%zu bufbytes=%zu\n",
                        curproc->p_pid, curlwp->l_lid, wl->wl_bufcount,
                        wl->wl_bufbytes));
  #endif
  
          /* Calculate amount of space needed to flush */
          flushsize = wapbl_transaction_len(wl);
          if (wapbl_verbose_commit) {
                  struct timespec ts;
                  getnanotime(&ts);
                  printf("%s: %lld.%09ld this transaction = %zu bytes\n",
                      __func__, (long long)ts.tv_sec,
                      (long)ts.tv_nsec, flushsize);
          }
  
          if (flushsize > (wl->wl_circ_size - wl->wl_reserved_bytes)) {
                  /*
                   * XXX this could be handled more gracefully, perhaps place
                   * only a partial transaction in the log and allow the
                   * remaining to flush without the protection of the journal.
                   */
                  panic("wapbl_flush: current transaction too big to flush");
          }
  
          error = wapbl_truncate(wl, flushsize);
          if (error)
                  goto out;
  
          off = wl->wl_head;
          KASSERT((off == 0) || (off >= wl->wl_circ_off));
          KASSERT((off == 0) || (off < wl->wl_circ_off + wl->wl_circ_size));
          error = wapbl_write_blocks(wl, &off);
          if (error)
                  goto out;
          error = wapbl_write_revocations(wl, &off);
          if (error)
                  goto out;
          error = wapbl_write_inodes(wl, &off);
          if (error)
                  goto out;
  
          reserved = 0;
          if (wl->wl_inohashcnt)
                  reserved = wapbl_transaction_inodes_len(wl);
  
          head = wl->wl_head;
          tail = wl->wl_tail;
  
          wapbl_advance_head(wl->wl_circ_size, wl->wl_circ_off, flushsize,
              &head, &tail);
  
          KASSERTMSG(head == off,
              "lost head! head=%"PRIdMAX" tail=%" PRIdMAX
              " off=%"PRIdMAX" flush=%zu",
              (intmax_t)head, (intmax_t)tail, (intmax_t)off,
              flushsize);
  
          /* Opportunistically move the tail forward if we can */
          mutex_enter(&wl->wl_mtx);
          delta = wl->wl_reclaimable_bytes;
          mutex_exit(&wl->wl_mtx);
          wapbl_advance_tail(wl->wl_circ_size, wl->wl_circ_off, delta,
              &head, &tail);
  
          error = wapbl_write_commit(wl, head, tail);
          if (error)
                  goto out;
  
          we = pool_get(&wapbl_entry_pool, PR_WAITOK);
  
  #ifdef WAPBL_DEBUG_BUFBYTES
          WAPBL_PRINTF(WAPBL_PRINT_FLUSH,
                  ("wapbl_flush: thread %d.%d head+=%zu tail+=%zu used=%zu"
                   " unsynced=%zu"
                   "\n\tbufcount=%zu bufbytes=%zu bcount=%zu deallocs=%d "
                   "inodes=%d\n",
                   curproc->p_pid, curlwp->l_lid, flushsize, delta,
                   wapbl_space_used(wl->wl_circ_size, head, tail),
                   wl->wl_unsynced_bufbytes, wl->wl_bufcount,
                   wl->wl_bufbytes, wl->wl_bcount, wl->wl_dealloccnt,
                   wl->wl_inohashcnt));
  #else
          WAPBL_PRINTF(WAPBL_PRINT_FLUSH,
                  ("wapbl_flush: thread %d.%d head+=%zu tail+=%zu used=%zu"
                   "\n\tbufcount=%zu bufbytes=%zu bcount=%zu deallocs=%d "
                   "inodes=%d\n",
                   curproc->p_pid, curlwp->l_lid, flushsize, delta,
                   wapbl_space_used(wl->wl_circ_size, head, tail),
                   wl->wl_bufcount, wl->wl_bufbytes, wl->wl_bcount,
                   wl->wl_dealloccnt, wl->wl_inohashcnt));
  #endif
  
  
          mutex_enter(&bufcache_lock);
          mutex_enter(&wl->wl_mtx);
  
          wl->wl_reserved_bytes = reserved;
          wl->wl_head = head;
          wl->wl_tail = tail;
          KASSERT(wl->wl_reclaimable_bytes >= delta);
          wl->wl_reclaimable_bytes -= delta;
          KDASSERT(wl->wl_dealloccnt == 0);
  #ifdef WAPBL_DEBUG_BUFBYTES
          wl->wl_unsynced_bufbytes += wl->wl_bufbytes;
  #endif
  
          we->we_wapbl = wl;
          we->we_bufcount = wl->wl_bufcount;
  #ifdef WAPBL_DEBUG_BUFBYTES
          we->we_unsynced_bufbytes = wl->wl_bufbytes;
  #endif
          we->we_reclaimable_bytes = flushsize;
          we->we_error = 0;
          SIMPLEQ_INSERT_TAIL(&wl->wl_entries, we, we_entries);
  
          /*
           * This flushes bufs in order than they were queued, so the LRU
           * order is preserved.
           */
          while ((bp = TAILQ_FIRST(&wl->wl_bufs)) != NULL) {
                  if (bbusy(bp, 0, 0, &wl->wl_mtx)) {
                          continue;
                  }
                  bp->b_iodone = wapbl_biodone;
                  bp->b_private = we;
  
                  bremfree(bp);
                  wapbl_remove_buf_locked(wl, bp);
                  mutex_exit(&wl->wl_mtx);
                  mutex_exit(&bufcache_lock);
                  bawrite(bp);
                  mutex_enter(&bufcache_lock);
                  mutex_enter(&wl->wl_mtx);
          }
          mutex_exit(&wl->wl_mtx);
          mutex_exit(&bufcache_lock);
  
  #if 0
          WAPBL_PRINTF(WAPBL_PRINT_FLUSH,
                       ("wapbl_flush thread %d.%d done flushing entries...\n",
                       curproc->p_pid, curlwp->l_lid));
  #endif
  
   wait_out:
  
          /*
           * If the waitfor flag is set, don't return until everything is
           * fully flushed and the on disk log is empty.
           */
          if (waitfor) {
                  error = wapbl_truncate(wl, wl->wl_circ_size -
                          wl->wl_reserved_bytes);
          }
  
   out:
          if (error) {
                  wl->wl_flush_abort(wl->wl_mount,
                      TAILQ_FIRST(&wl->wl_dealloclist));
          }
  
  #ifdef WAPBL_DEBUG_PRINT
          if (error) {
                  pid_t pid = -1;
                  lwpid_t lid = -1;
                  if (curproc)
                          pid = curproc->p_pid;
                  if (curlwp)
                          lid = curlwp->l_lid;
                  mutex_enter(&wl->wl_mtx);
  #ifdef WAPBL_DEBUG_BUFBYTES
                  WAPBL_PRINTF(WAPBL_PRINT_ERROR,
                      ("wapbl_flush: thread %d.%d aborted flush: "
                      "error = %d\n"
                      "\tbufcount=%zu bufbytes=%zu bcount=%zu "
                      "deallocs=%d inodes=%d\n"
                      "\terrcnt = %d, reclaimable=%zu reserved=%zu "
                      "unsynced=%zu\n",
                      pid, lid, error, wl->wl_bufcount,
                      wl->wl_bufbytes, wl->wl_bcount,
                      wl->wl_dealloccnt, wl->wl_inohashcnt,
                      wl->wl_error_count, wl->wl_reclaimable_bytes,
                      wl->wl_reserved_bytes, wl->wl_unsynced_bufbytes));
                  SIMPLEQ_FOREACH(we, &wl->wl_entries, we_entries) {
                          WAPBL_PRINTF(WAPBL_PRINT_ERROR,
                              ("\tentry: bufcount = %zu, reclaimable = %zu, "
                               "error = %d, unsynced = %zu\n",
                               we->we_bufcount, we->we_reclaimable_bytes,
                               we->we_error, we->we_unsynced_bufbytes));
                  }
  #else
                  WAPBL_PRINTF(WAPBL_PRINT_ERROR,
                      ("wapbl_flush: thread %d.%d aborted flush: "
                       "error = %d\n"
                       "\tbufcount=%zu bufbytes=%zu bcount=%zu "
                       "deallocs=%d inodes=%d\n"
                       "\terrcnt = %d, reclaimable=%zu reserved=%zu\n",
                       pid, lid, error, wl->wl_bufcount,
                       wl->wl_bufbytes, wl->wl_bcount,
                       wl->wl_dealloccnt, wl->wl_inohashcnt,
                       wl->wl_error_count, wl->wl_reclaimable_bytes,
                       wl->wl_reserved_bytes));
                  SIMPLEQ_FOREACH(we, &wl->wl_entries, we_entries) {
                          WAPBL_PRINTF(WAPBL_PRINT_ERROR,
                              ("\tentry: bufcount = %zu, reclaimable = %zu, "
                               "error = %d\n", we->we_bufcount,
                               we->we_reclaimable_bytes, we->we_error));
                  }
  #endif
                  mutex_exit(&wl->wl_mtx);
          }
  #endif
  
          rw_exit(&wl->wl_rwlock);
          return error;
  }
  
  /****************************************************************/
  
  void
  wapbl_jlock_assert(struct wapbl *wl)
  {
  
          KASSERT(rw_lock_held(&wl->wl_rwlock));
  }
  
  void
  wapbl_junlock_assert(struct wapbl *wl)
  {
  
          KASSERT(!rw_write_held(&wl->wl_rwlock));
  }
  
  /****************************************************************/
  
  /* locks missing */
  void
  wapbl_print(struct wapbl *wl,
                  int full,
                  void (*pr)(const char *, ...))
  {
          struct buf *bp;
          struct wapbl_entry *we;
          (*pr)("wapbl %p", wl);
          (*pr)("\nlogvp = %p, devvp = %p, logpbn = %"PRId64"\n",
                wl->wl_logvp, wl->wl_devvp, wl->wl_logpbn);
          (*pr)("circ = %zu, header = %zu, head = %"PRIdMAX" tail = %"PRIdMAX"\n",
                wl->wl_circ_size, wl->wl_circ_off,
                (intmax_t)wl->wl_head, (intmax_t)wl->wl_tail);
          (*pr)("fs_dev_bshift = %d, log_dev_bshift = %d\n",
                wl->wl_log_dev_bshift, wl->wl_fs_dev_bshift);
  #ifdef WAPBL_DEBUG_BUFBYTES
          (*pr)("bufcount = %zu, bufbytes = %zu bcount = %zu reclaimable = %zu "
                "reserved = %zu errcnt = %d unsynced = %zu\n",
                wl->wl_bufcount, wl->wl_bufbytes, wl->wl_bcount,
                wl->wl_reclaimable_bytes, wl->wl_reserved_bytes,
                                  wl->wl_error_count, wl->wl_unsynced_bufbytes);
  #else
          (*pr)("bufcount = %zu, bufbytes = %zu bcount = %zu reclaimable = %zu "
                "reserved = %zu errcnt = %d\n", wl->wl_bufcount, wl->wl_bufbytes,
                wl->wl_bcount, wl->wl_reclaimable_bytes, wl->wl_reserved_bytes,
                                  wl->wl_error_count);
  #endif
          (*pr)("\tdealloccnt = %d, dealloclim = %d\n",
                wl->wl_dealloccnt, wl->wl_dealloclim);
          (*pr)("\tinohashcnt = %d, inohashmask = 0x%08x\n",
                wl->wl_inohashcnt, wl->wl_inohashmask);
          (*pr)("entries:\n");
          SIMPLEQ_FOREACH(we, &wl->wl_entries, we_entries) {
  #ifdef WAPBL_DEBUG_BUFBYTES
                  (*pr)("\tbufcount = %zu, reclaimable = %zu, error = %d, "
                        "unsynced = %zu\n",
                        we->we_bufcount, we->we_reclaimable_bytes,
                        we->we_error, we->we_unsynced_bufbytes);
  #else
                  (*pr)("\tbufcount = %zu, reclaimable = %zu, error = %d\n",
                        we->we_bufcount, we->we_reclaimable_bytes, we->we_error);
  #endif
          }
          if (full) {
                  int cnt = 0;
                  (*pr)("bufs =");
                  TAILQ_FOREACH(bp, &wl->wl_bufs, b_wapbllist) {
                          if (!TAILQ_NEXT(bp, b_wapbllist)) {
                                  (*pr)(" %p", bp);
                          } else if ((++cnt % 6) == 0) {
                                  (*pr)(" %p,\n\t", bp);
                          } else {
                                  (*pr)(" %p,", bp);
                          }
                  }
                  (*pr)("\n");
  
                  (*pr)("dealloced blks = ");
                  {
                          struct wapbl_dealloc *wd;
                          cnt = 0;
                          TAILQ_FOREACH(wd, &wl->wl_dealloclist, wd_entries) {
                                  (*pr)(" %"PRId64":%d,",
                                        wd->wd_blkno,
                                        wd->wd_len);
                                  if ((++cnt % 4) == 0) {
                                          (*pr)("\n\t");
                                  }
                          }
                  }
                  (*pr)("\n");
  
                  (*pr)("registered inodes = ");
                  {
                          int i;
                          cnt = 0;
                          for (i = 0; i <= wl->wl_inohashmask; i++) {
                                  struct wapbl_ino_head *wih;
                                  struct wapbl_ino *wi;
  
                                  wih = &wl->wl_inohash[i];
                                  LIST_FOREACH(wi, wih, wi_hash) {
                                          if (wi->wi_ino == 0)
                                                  continue;
                                          (*pr)(" %"PRIu64"/0%06"PRIo32",",
                                              wi->wi_ino, wi->wi_mode);
                                          if ((++cnt % 4) == 0) {
                                                  (*pr)("\n\t");
                                          }
                                  }
                          }
                          (*pr)("\n");
                  }
  
                  (*pr)("iobufs free =");
                  TAILQ_FOREACH(bp, &wl->wl_iobufs, b_wapbllist) {
                          if (!TAILQ_NEXT(bp, b_wapbllist)) {
                                  (*pr)(" %p", bp);
                          } else if ((++cnt % 6) == 0) {
                                  (*pr)(" %p,\n\t", bp);
                          } else {
                                  (*pr)(" %p,", bp);
                          }
                  }
                  (*pr)("\n");
  
                  (*pr)("iobufs busy =");
                  TAILQ_FOREACH(bp, &wl->wl_iobufs_busy, b_wapbllist) {
                          if (!TAILQ_NEXT(bp, b_wapbllist)) {
                                  (*pr)(" %p", bp);
                          } else if ((++cnt % 6) == 0) {
                                  (*pr)(" %p,\n\t", bp);
                          } else {
                                  (*pr)(" %p,", bp);
                          }
                  }
                  (*pr)("\n");
          }
  }
  
  #if defined(WAPBL_DEBUG) || defined(DDB)
  void
  wapbl_dump(struct wapbl *wl)
  {
  #if defined(WAPBL_DEBUG)
          if (!wl)
                  wl = wapbl_debug_wl;
  #endif
          if (!wl)
                  return;
          wapbl_print(wl, 1, printf);
  }
  #endif
  
  /****************************************************************/
  
  int
  wapbl_register_deallocation(struct wapbl *wl, daddr_t blk, int len, bool force,
      void **cookiep)
  {
          struct wapbl_dealloc *wd;
          int error = 0;
  
          wapbl_jlock_assert(wl);
  
          mutex_enter(&wl->wl_mtx);
  
          if (__predict_false(wl->wl_dealloccnt >= wl->wl_dealloclim)) {
                  if (!force) {
                          error = EAGAIN;
                          goto out;
                  }
  
                  /*
                   * Forced registration can only be used when:
                   * 1) the caller can't cope with failure
                   * 2) the path can be triggered only bounded, small
                   *    times per transaction
                   * If this is not fullfilled, and the path would be triggered
                   * many times, this could overflow maximum transaction size
                   * and panic later.
                   */
                  printf("%s: forced dealloc registration over limit: %d >= %d\n",
                          wl->wl_mount->mnt_stat.f_mntonname,
                          wl->wl_dealloccnt, wl->wl_dealloclim);
          }
  
          wl->wl_dealloccnt++;
          mutex_exit(&wl->wl_mtx);
  
          wd = pool_get(&wapbl_dealloc_pool, PR_WAITOK);
          wd->wd_blkno = blk;
          wd->wd_len = len;
  
          mutex_enter(&wl->wl_mtx);
          TAILQ_INSERT_TAIL(&wl->wl_dealloclist, wd, wd_entries);
  
          if (cookiep)
                  *cookiep = wd;
  
   out:
          mutex_exit(&wl->wl_mtx);
  
          WAPBL_PRINTF(WAPBL_PRINT_ALLOC,
              ("wapbl_register_deallocation: blk=%"PRId64" len=%d error=%d\n",
              blk, len, error));
  
          return error;
  }
  
  static void
  wapbl_deallocation_free(struct wapbl *wl, struct wapbl_dealloc *wd,
          bool locked)
  {
          KASSERT(!locked
              || rw_lock_held(&wl->wl_rwlock) || mutex_owned(&wl->wl_mtx));
  
          if (!locked)
                  mutex_enter(&wl->wl_mtx);
  
          TAILQ_REMOVE(&wl->wl_dealloclist, wd, wd_entries);
          wl->wl_dealloccnt--;
  
          if (!locked)
                  mutex_exit(&wl->wl_mtx);
  
          pool_put(&wapbl_dealloc_pool, wd);
  }
  
  void
  wapbl_unregister_deallocation(struct wapbl *wl, void *cookie)
  {
          KASSERT(cookie != NULL);
          wapbl_deallocation_free(wl, cookie, false);
  }
  
  /****************************************************************/
  
  static void
  wapbl_inodetrk_init(struct wapbl *wl, u_int size)
  {
  
          wl->wl_inohash = hashinit(size, HASH_LIST, true, &wl->wl_inohashmask);
          if (atomic_inc_uint_nv(&wapbl_ino_pool_refcount) == 1) {
                  pool_init(&wapbl_ino_pool, sizeof(struct wapbl_ino), 0, 0, 0,
                      "wapblinopl", &pool_allocator_nointr, IPL_NONE);
          }
  }
  
  static void
  wapbl_inodetrk_free(struct wapbl *wl)
  {
  
          /* XXX this KASSERT needs locking/mutex analysis */
          KASSERT(wl->wl_inohashcnt == 0);
          hashdone(wl->wl_inohash, HASH_LIST, wl->wl_inohashmask);
          membar_release();
          if (atomic_dec_uint_nv(&wapbl_ino_pool_refcount) == 0) {
                  membar_acquire();
                  pool_destroy(&wapbl_ino_pool);
          }
  }
  
  static struct wapbl_ino *
  wapbl_inodetrk_get(struct wapbl *wl, ino_t ino)
  {
          struct wapbl_ino_head *wih;
          struct wapbl_ino *wi;
  
          KASSERT(mutex_owned(&wl->wl_mtx));
  
          wih = &wl->wl_inohash[ino & wl->wl_inohashmask];
          LIST_FOREACH(wi, wih, wi_hash) {
                  if (ino == wi->wi_ino)
                          return wi;
          }
          return 0;
  }
  
  void
  wapbl_register_inode(struct wapbl *wl, ino_t ino, mode_t mode)
  {
          struct wapbl_ino_head *wih;
          struct wapbl_ino *wi;
  
          wi = pool_get(&wapbl_ino_pool, PR_WAITOK);
  
          mutex_enter(&wl->wl_mtx);
          if (wapbl_inodetrk_get(wl, ino) == NULL) {
                  wi->wi_ino = ino;
                  wi->wi_mode = mode;
                  wih = &wl->wl_inohash[ino & wl->wl_inohashmask];
                  LIST_INSERT_HEAD(wih, wi, wi_hash);
                  wl->wl_inohashcnt++;
                  WAPBL_PRINTF(WAPBL_PRINT_INODE,
                      ("wapbl_register_inode: ino=%"PRId64"\n", ino));
                  mutex_exit(&wl->wl_mtx);
          } else {
                  mutex_exit(&wl->wl_mtx);
                  pool_put(&wapbl_ino_pool, wi);
          }
  }
  
  void
  wapbl_unregister_inode(struct wapbl *wl, ino_t ino, mode_t mode)
  {
          struct wapbl_ino *wi;
  
          mutex_enter(&wl->wl_mtx);
          wi = wapbl_inodetrk_get(wl, ino);
          if (wi) {
                  WAPBL_PRINTF(WAPBL_PRINT_INODE,
                      ("wapbl_unregister_inode: ino=%"PRId64"\n", ino));
                  KASSERT(wl->wl_inohashcnt > 0);
                  wl->wl_inohashcnt--;
                  LIST_REMOVE(wi, wi_hash);
                  mutex_exit(&wl->wl_mtx);
  
                  pool_put(&wapbl_ino_pool, wi);
          } else {
                  mutex_exit(&wl->wl_mtx);
          }
  }
  
  /****************************************************************/
  
  /*
   * wapbl_transaction_inodes_len(wl)
   *
   *      Calculate the number of bytes required for inode registration
   *      log records in wl.
   */
  static inline size_t
  wapbl_transaction_inodes_len(struct wapbl *wl)
  {
          int blocklen = 1<<wl->wl_log_dev_bshift;
          int iph;
  
          /* Calculate number of inodes described in a inodelist header */
          iph = (blocklen - offsetof(struct wapbl_wc_inodelist, wc_inodes)) /
              sizeof(((struct wapbl_wc_inodelist *)0)->wc_inodes[0]);
  
          KASSERT(iph > 0);
  
          return MAX(1, howmany(wl->wl_inohashcnt, iph)) * blocklen;
  }
  
  
  /*
   * wapbl_transaction_len(wl)
   *
   *      Calculate number of bytes required for all log records in wl.
   */
  static size_t
  wapbl_transaction_len(struct wapbl *wl)
  {
          int blocklen = 1<<wl->wl_log_dev_bshift;
          size_t len;
  
          /* Calculate number of blocks described in a blocklist header */
          len = wl->wl_bcount;
          len += howmany(wl->wl_bufcount, wl->wl_brperjblock) * blocklen;
          len += howmany(wl->wl_dealloccnt, wl->wl_brperjblock) * blocklen;
          len += wapbl_transaction_inodes_len(wl);
  
          return len;
  }
  
  /*
   * wapbl_cache_sync(wl, msg)
   *
   *      Issue DIOCCACHESYNC to wl->wl_devvp.
   *
   *      If sysctl(vfs.wapbl.verbose_commit) >= 2, print a message
   *      including msg about the duration of the cache sync.
   */
  static int
  wapbl_cache_sync(struct wapbl *wl, const char *msg)
  {
          const bool verbose = wapbl_verbose_commit >= 2;
          struct bintime start_time;
          int force = 1;
          int error;
  
          /* Skip full cache sync if disabled */
          if (!wapbl_flush_disk_cache) {
                  return 0;
          }
          if (verbose) {
                  bintime(&start_time);
          }
          error = VOP_IOCTL(wl->wl_devvp, DIOCCACHESYNC, &force,
              FWRITE, FSCRED);
          if (error) {
                  WAPBL_PRINTF(WAPBL_PRINT_ERROR,
                      ("wapbl_cache_sync: DIOCCACHESYNC on dev 0x%jx "
                      "returned %d\n", (uintmax_t)wl->wl_devvp->v_rdev, error));
          }
          if (verbose) {
                  struct bintime d;
                  struct timespec ts;
  
                  bintime(&d);
                  bintime_sub(&d, &start_time);
                  bintime2timespec(&d, &ts);
                  printf("wapbl_cache_sync: %s: dev 0x%jx %ju.%09lu\n",
                      msg, (uintmax_t)wl->wl_devvp->v_rdev,
                      (uintmax_t)ts.tv_sec, ts.tv_nsec);
          }
  
          wl->wl_ev_cacheflush.ev_count++;
  
          return error;
  }
  
  /*
   * wapbl_write_commit(wl, head, tail)
   *
   *      Issue a disk cache sync to wait for all pending writes to the
   *      log to complete, and then synchronously commit the current
   *      circular queue head and tail to the log, in the next of two
   *      locations for commit headers on disk.
   *
   *      Increment the generation number.  If the generation number
   *      rolls over to zero, then a subsequent commit would appear to
   *      have an older generation than this one -- in that case, issue a
   *      duplicate commit to avoid this.
   *
   *      => Caller must have exclusive access to wl, either by holding
   *      wl->wl_rwlock for writer or by being wapbl_start before anyone
   *      else has seen wl.
   */
  static int
  wapbl_write_commit(struct wapbl *wl, off_t head, off_t tail)
  {
          struct wapbl_wc_header *wc = wl->wl_wc_header;
          struct timespec ts;
          int error;
          daddr_t pbn;
  
          error = wapbl_buffered_flush(wl, true);
          if (error)
                  return error;
          /*
           * Flush disk cache to ensure that blocks we've written are actually
           * written to the stable storage before the commit header.
           * This flushes to disk not only journal blocks, but also all
           * metadata blocks, written asynchronously since previous commit.
           *
           * XXX Calc checksum here, instead we do this for now
           */
          wapbl_cache_sync(wl, "1");
  
          wc->wc_head = head;
          wc->wc_tail = tail;
          wc->wc_checksum = 0;
          wc->wc_version = 1;
          getnanotime(&ts);
          wc->wc_time = ts.tv_sec;
          wc->wc_timensec = ts.tv_nsec;
  
          WAPBL_PRINTF(WAPBL_PRINT_WRITE,
              ("wapbl_write_commit: head = %"PRIdMAX "tail = %"PRIdMAX"\n",
              (intmax_t)head, (intmax_t)tail));
  
          /*
           * write the commit header.
           *
           * XXX if generation will rollover, then first zero
           * over second commit header before trying to write both headers.
           */
  
          pbn = wl->wl_logpbn + (wc->wc_generation % 2);
  #ifdef _KERNEL
          pbn = btodb(pbn << wc->wc_log_dev_bshift);
  #endif
          error = wapbl_buffered_write(wc, wc->wc_len, wl, pbn, WAPBL_JFLAGS(wl));
          if (error)
                  return error;
          error = wapbl_buffered_flush(wl, true);
          if (error)
                  return error;
  
          /*
           * Flush disk cache to ensure that the commit header is actually
           * written before meta data blocks. Commit block is written using
           * FUA when enabled, in that case this flush is not needed.
           */
          if (!WAPBL_USE_FUA(wl))
                  wapbl_cache_sync(wl, "2");
  
          /*
           * If the generation number was zero, write it out a second time.
           * This handles initialization and generation number rollover
           */
          if (wc->wc_generation++ == 0) {
                  error = wapbl_write_commit(wl, head, tail);
                  /*
                   * This panic should be able to be removed if we do the
                   * zero'ing mentioned above, and we are certain to roll
                   * back generation number on failure.
                   */
                  if (error)
                          panic("wapbl_write_commit: error writing duplicate "
                                "log header: %d", error);
          }
  
          wl->wl_ev_commit.ev_count++;
  
          return 0;
  }
  
  /*
   * wapbl_write_blocks(wl, offp)
   *
   *      Write all pending physical blocks in the current transaction
   *      from wapbl_add_buf to the log on disk, adding to the circular
   *      queue head at byte offset *offp, and returning the new head's
   *      byte offset in *offp.
   */
  static int
  wapbl_write_blocks(struct wapbl *wl, off_t *offp)
  {
          struct wapbl_wc_blocklist *wc =
              (struct wapbl_wc_blocklist *)wl->wl_wc_scratch;
          int blocklen = 1<<wl->wl_log_dev_bshift;
          struct buf *bp;
          off_t off = *offp;
          int error;
          size_t padding;
  
          KASSERT(rw_write_held(&wl->wl_rwlock));
  
          bp = TAILQ_FIRST(&wl->wl_bufs);
  
          while (bp) {
                  int cnt;
                  struct buf *obp = bp;
  
                  KASSERT(bp->b_flags & B_LOCKED);
  
                  wc->wc_type = WAPBL_WC_BLOCKS;
                  wc->wc_len = blocklen;
                  wc->wc_blkcount = 0;
                  wc->wc_unused = 0;
                  while (bp && (wc->wc_blkcount < wl->wl_brperjblock)) {
                          /*
                           * Make sure all the physical block numbers are up to
                           * date.  If this is not always true on a given
                           * filesystem, then VOP_BMAP must be called.  We
                           * could call VOP_BMAP here, or else in the filesystem
                           * specific flush callback, although neither of those
                           * solutions allow us to take the vnode lock.  If a
                           * filesystem requires that we must take the vnode lock
                           * to call VOP_BMAP, then we can probably do it in
                           * bwrite when the vnode lock should already be held
                           * by the invoking code.
                           */
                          KASSERT((bp->b_vp->v_type == VBLK) ||
                                   (bp->b_blkno != bp->b_lblkno));
                          KASSERT(bp->b_blkno > 0);
  
                          wc->wc_blocks[wc->wc_blkcount].wc_daddr = bp->b_blkno;
                          wc->wc_blocks[wc->wc_blkcount].wc_dlen = bp->b_bcount;
                          wc->wc_len += bp->b_bcount;
                          wc->wc_blkcount++;
                          bp = TAILQ_NEXT(bp, b_wapbllist);
                  }
                  if (wc->wc_len % blocklen != 0) {
                          padding = blocklen - wc->wc_len % blocklen;
                          wc->wc_len += padding;
                  } else {
                          padding = 0;
                  }
  
                  WAPBL_PRINTF(WAPBL_PRINT_WRITE,
                      ("wapbl_write_blocks: len = %u (padding %zu) off = %"PRIdMAX"\n",
                      wc->wc_len, padding, (intmax_t)off));
  
                  error = wapbl_circ_write(wl, wc, blocklen, &off);
                  if (error)
                          return error;
                  bp = obp;
                  cnt = 0;
                  while (bp && (cnt++ < wl->wl_brperjblock)) {
                          error = wapbl_circ_write(wl, bp->b_data,
                              bp->b_bcount, &off);
                          if (error)
                                  return error;
                          bp = TAILQ_NEXT(bp, b_wapbllist);
                  }
                  if (padding) {
                          void *zero;
  
                          zero = wapbl_alloc(padding);
                          memset(zero, 0, padding);
                          error = wapbl_circ_write(wl, zero, padding, &off);
                          wapbl_free(zero, padding);
                          if (error)
                                  return error;
                  }
          }
          *offp = off;
          return 0;
  }
  
  /*
   * wapbl_write_revocations(wl, offp)
   *
   *      Write all pending deallocations in the current transaction from
   *      wapbl_register_deallocation to the log on disk, adding to the
   *      circular queue's head at byte offset *offp, and returning the
   *      new head's byte offset in *offp.
   */
  static int
  wapbl_write_revocations(struct wapbl *wl, off_t *offp)
  {
          struct wapbl_wc_blocklist *wc =
              (struct wapbl_wc_blocklist *)wl->wl_wc_scratch;
          struct wapbl_dealloc *wd, *lwd;
          int blocklen = 1<<wl->wl_log_dev_bshift;
          off_t off = *offp;
          int error;
  
          KASSERT(rw_write_held(&wl->wl_rwlock));
  
          if (wl->wl_dealloccnt == 0)
                  return 0;
  
          while ((wd = TAILQ_FIRST(&wl->wl_dealloclist)) != NULL) {
                  wc->wc_type = WAPBL_WC_REVOCATIONS;
                  wc->wc_len = blocklen;
                  wc->wc_blkcount = 0;
                  wc->wc_unused = 0;
                  while (wd && (wc->wc_blkcount < wl->wl_brperjblock)) {
                          wc->wc_blocks[wc->wc_blkcount].wc_daddr =
                              wd->wd_blkno;
                          wc->wc_blocks[wc->wc_blkcount].wc_dlen =
                              wd->wd_len;
                          wc->wc_blkcount++;
  
                          wd = TAILQ_NEXT(wd, wd_entries);
                  }
                  WAPBL_PRINTF(WAPBL_PRINT_WRITE,
                      ("wapbl_write_revocations: len = %u off = %"PRIdMAX"\n",
                      wc->wc_len, (intmax_t)off));
                  error = wapbl_circ_write(wl, wc, blocklen, &off);
                  if (error)
                          return error;
  
                  /* free all successfully written deallocs */
                  lwd = wd;
                  while ((wd = TAILQ_FIRST(&wl->wl_dealloclist)) != NULL) {
                          if (wd == lwd)
                                  break;
                          wapbl_deallocation_free(wl, wd, true);
                  }
          }
          *offp = off;
          return 0;
  }
  
  /*
   * wapbl_write_inodes(wl, offp)
   *
   *      Write all pending inode allocations in the current transaction
   *      from wapbl_register_inode to the log on disk, adding to the
   *      circular queue's head at byte offset *offp and returning the
   *      new head's byte offset in *offp.
   */
  static int
  wapbl_write_inodes(struct wapbl *wl, off_t *offp)
  {
          struct wapbl_wc_inodelist *wc =
              (struct wapbl_wc_inodelist *)wl->wl_wc_scratch;
          int i;
          int blocklen = 1 << wl->wl_log_dev_bshift;
          off_t off = *offp;
          int error;
  
          struct wapbl_ino_head *wih;
          struct wapbl_ino *wi;
          int iph;
  
          iph = (blocklen - offsetof(struct wapbl_wc_inodelist, wc_inodes)) /
              sizeof(((struct wapbl_wc_inodelist *)0)->wc_inodes[0]);
  
          i = 0;
          wih = &wl->wl_inohash[0];
          wi = 0;
          do {
                  wc->wc_type = WAPBL_WC_INODES;
                  wc->wc_len = blocklen;
                  wc->wc_inocnt = 0;
                  wc->wc_clear = (i == 0);
                  while ((i < wl->wl_inohashcnt) && (wc->wc_inocnt < iph)) {
                          while (!wi) {
                                  KASSERT((wih - &wl->wl_inohash[0])
                                      <= wl->wl_inohashmask);
                                  wi = LIST_FIRST(wih++);
                          }
                          wc->wc_inodes[wc->wc_inocnt].wc_inumber = wi->wi_ino;
                          wc->wc_inodes[wc->wc_inocnt].wc_imode = wi->wi_mode;
                          wc->wc_inocnt++;
                          i++;
                          wi = LIST_NEXT(wi, wi_hash);
                  }
                  WAPBL_PRINTF(WAPBL_PRINT_WRITE,
                      ("wapbl_write_inodes: len = %u off = %"PRIdMAX"\n",
                      wc->wc_len, (intmax_t)off));
                  error = wapbl_circ_write(wl, wc, blocklen, &off);
                  if (error)
                          return error;
          } while (i < wl->wl_inohashcnt);
  
          *offp = off;
          return 0;
  }
  
  #endif /* _KERNEL */
  
  /****************************************************************/
  
  struct wapbl_blk {
          LIST_ENTRY(wapbl_blk) wb_hash;
          daddr_t wb_blk;
          off_t wb_off; /* Offset of this block in the log */
  };
  #define WAPBL_BLKPOOL_MIN 83
  
  static void
  wapbl_blkhash_init(struct wapbl_replay *wr, u_int size)
  {
          if (size < WAPBL_BLKPOOL_MIN)
                  size = WAPBL_BLKPOOL_MIN;
          KASSERT(wr->wr_blkhash == 0);
  #ifdef _KERNEL
          wr->wr_blkhash = hashinit(size, HASH_LIST, true, &wr->wr_blkhashmask);
  #else /* ! _KERNEL */
          /* Manually implement hashinit */
          {
                  unsigned long i, hashsize;
                  for (hashsize = 1; hashsize < size; hashsize <<= 1)
                          continue;
                  wr->wr_blkhash = wapbl_alloc(hashsize * sizeof(*wr->wr_blkhash));
                  for (i = 0; i < hashsize; i++)
                          LIST_INIT(&wr->wr_blkhash[i]);
                  wr->wr_blkhashmask = hashsize - 1;
          }
  #endif /* ! _KERNEL */
  }
  
  static void
  wapbl_blkhash_free(struct wapbl_replay *wr)
  {
          KASSERT(wr->wr_blkhashcnt == 0);
  #ifdef _KERNEL
          hashdone(wr->wr_blkhash, HASH_LIST, wr->wr_blkhashmask);
  #else /* ! _KERNEL */
          wapbl_free(wr->wr_blkhash,
              (wr->wr_blkhashmask + 1) * sizeof(*wr->wr_blkhash));
  #endif /* ! _KERNEL */
  }
  
  static struct wapbl_blk *
  wapbl_blkhash_get(struct wapbl_replay *wr, daddr_t blk)
  {
          struct wapbl_blk_head *wbh;
          struct wapbl_blk *wb;
          wbh = &wr->wr_blkhash[blk & wr->wr_blkhashmask];
          LIST_FOREACH(wb, wbh, wb_hash) {
                  if (blk == wb->wb_blk)
                          return wb;
          }
          return 0;
  }
  
  static void
  wapbl_blkhash_ins(struct wapbl_replay *wr, daddr_t blk, off_t off)
  {
          struct wapbl_blk_head *wbh;
          struct wapbl_blk *wb;
          wb = wapbl_blkhash_get(wr, blk);
          if (wb) {
                  KASSERT(wb->wb_blk == blk);
                  wb->wb_off = off;
          } else {
                  wb = wapbl_alloc(sizeof(*wb));
                  wb->wb_blk = blk;
                  wb->wb_off = off;
                  wbh = &wr->wr_blkhash[blk & wr->wr_blkhashmask];
                  LIST_INSERT_HEAD(wbh, wb, wb_hash);
                  wr->wr_blkhashcnt++;
          }
  }
  
  static void
  wapbl_blkhash_rem(struct wapbl_replay *wr, daddr_t blk)
  {
          struct wapbl_blk *wb = wapbl_blkhash_get(wr, blk);
          if (wb) {
                  KASSERT(wr->wr_blkhashcnt > 0);
                  wr->wr_blkhashcnt--;
                  LIST_REMOVE(wb, wb_hash);
                  wapbl_free(wb, sizeof(*wb));
          }
  }
  
  static void
  wapbl_blkhash_clear(struct wapbl_replay *wr)
  {
          unsigned long i;
          for (i = 0; i <= wr->wr_blkhashmask; i++) {
                  struct wapbl_blk *wb;
  
                  while ((wb = LIST_FIRST(&wr->wr_blkhash[i]))) {
                          KASSERT(wr->wr_blkhashcnt > 0);
                          wr->wr_blkhashcnt--;
                          LIST_REMOVE(wb, wb_hash);
                          wapbl_free(wb, sizeof(*wb));
                  }
          }
          KASSERT(wr->wr_blkhashcnt == 0);
  }
  
  /****************************************************************/
  
  /*
   * wapbl_circ_read(wr, data, len, offp)
   *
   *      Read len bytes into data from the circular queue of wr,
   *      starting at the linear byte offset *offp, and returning the new
   *      linear byte offset in *offp.
   *
   *      If the starting linear byte offset precedes wr->wr_circ_off,
   *      the read instead begins at wr->wr_circ_off.  XXX WTF?  This
   *      should be a KASSERT, not a conditional.
   */
  static int
  wapbl_circ_read(struct wapbl_replay *wr, void *data, size_t len, off_t *offp)
  {
          size_t slen;
          off_t off = *offp;
          int error;
          daddr_t pbn;
  
          KASSERT(((len >> wr->wr_log_dev_bshift) <<
              wr->wr_log_dev_bshift) == len);
  
          if (off < wr->wr_circ_off)
                  off = wr->wr_circ_off;
          slen = wr->wr_circ_off + wr->wr_circ_size - off;
          if (slen < len) {
                  pbn = wr->wr_logpbn + (off >> wr->wr_log_dev_bshift);
  #ifdef _KERNEL
                  pbn = btodb(pbn << wr->wr_log_dev_bshift);
  #endif
                  error = wapbl_read(data, slen, wr->wr_devvp, pbn);
                  if (error)
                          return error;
                  data = (uint8_t *)data + slen;
                  len -= slen;
                  off = wr->wr_circ_off;
          }
          pbn = wr->wr_logpbn + (off >> wr->wr_log_dev_bshift);
  #ifdef _KERNEL
          pbn = btodb(pbn << wr->wr_log_dev_bshift);
  #endif
          error = wapbl_read(data, len, wr->wr_devvp, pbn);
          if (error)
                  return error;
          off += len;
          if (off >= wr->wr_circ_off + wr->wr_circ_size)
                  off = wr->wr_circ_off;
          *offp = off;
          return 0;
  }
  
  /*
   * wapbl_circ_advance(wr, len, offp)
   *
   *      Compute the linear byte offset of the circular queue of wr that
   *      is len bytes past *offp, and store it in *offp.
   *
   *      This is as if wapbl_circ_read, but without actually reading
   *      anything.
   *
   *      If the starting linear byte offset precedes wr->wr_circ_off, it
   *      is taken to be wr->wr_circ_off instead.  XXX WTF?  This should
   *      be a KASSERT, not a conditional.
   */
  static void
  wapbl_circ_advance(struct wapbl_replay *wr, size_t len, off_t *offp)
  {
          size_t slen;
          off_t off = *offp;
  
          KASSERT(((len >> wr->wr_log_dev_bshift) <<
              wr->wr_log_dev_bshift) == len);
  
          if (off < wr->wr_circ_off)
                  off = wr->wr_circ_off;
          slen = wr->wr_circ_off + wr->wr_circ_size - off;
          if (slen < len) {
                  len -= slen;
                  off = wr->wr_circ_off;
          }
          off += len;
          if (off >= wr->wr_circ_off + wr->wr_circ_size)
                  off = wr->wr_circ_off;
          *offp = off;
  }
  
  /****************************************************************/
  
  int
  wapbl_replay_start(struct wapbl_replay **wrp, struct vnode *vp,
          daddr_t off, size_t count, size_t blksize)
  {
          struct wapbl_replay *wr;
          int error;
          struct vnode *devvp;
          daddr_t logpbn;
          uint8_t *scratch;
          struct wapbl_wc_header *wch;
          struct wapbl_wc_header *wch2;
          /* Use this until we read the actual log header */
          int log_dev_bshift = ilog2(blksize);
          size_t used;
          daddr_t pbn;
  
          WAPBL_PRINTF(WAPBL_PRINT_REPLAY,
              ("wapbl_replay_start: vp=%p off=%"PRId64 " count=%zu blksize=%zu\n",
              vp, off, count, blksize));
  
          if (off < 0)
                  return EINVAL;
  
          if (blksize < DEV_BSIZE)
                  return EINVAL;
          if (blksize % DEV_BSIZE)
                  return EINVAL;
  
  #ifdef _KERNEL
  #if 0
          /* XXX vp->v_size isn't reliably set for VBLK devices,
           * especially root.  However, we might still want to verify
           * that the full load is readable */
          if ((off + count) * blksize > vp->v_size)
                  return EINVAL;
  #endif
          if ((error = VOP_BMAP(vp, off, &devvp, &logpbn, 0)) != 0) {
                  return error;
          }
  #else /* ! _KERNEL */
          devvp = vp;
          logpbn = off;
  #endif /* ! _KERNEL */
  
          scratch = wapbl_alloc(MAXBSIZE);
  
          pbn = logpbn;
  #ifdef _KERNEL
          pbn = btodb(pbn << log_dev_bshift);
  #endif
          error = wapbl_read(scratch, 2<<log_dev_bshift, devvp, pbn);
          if (error)
                  goto errout;
  
          wch = (struct wapbl_wc_header *)scratch;
          wch2 =
              (struct wapbl_wc_header *)(scratch + (1<<log_dev_bshift));
          /* XXX verify checksums and magic numbers */
          if (wch->wc_type != WAPBL_WC_HEADER) {
                  printf("Unrecognized wapbl magic: 0x%08x\n", wch->wc_type);
                  error = EFTYPE;
                  goto errout;
          }
  
          if (wch2->wc_generation > wch->wc_generation)
                  wch = wch2;
  
          wr = wapbl_calloc(1, sizeof(*wr));
  
          wr->wr_logvp = vp;
          wr->wr_devvp = devvp;
          wr->wr_logpbn = logpbn;
  
          wr->wr_scratch = scratch;
  
          wr->wr_log_dev_bshift = wch->wc_log_dev_bshift;
          wr->wr_fs_dev_bshift = wch->wc_fs_dev_bshift;
          wr->wr_circ_off = wch->wc_circ_off;
          wr->wr_circ_size = wch->wc_circ_size;
          wr->wr_generation = wch->wc_generation;
  
          used = wapbl_space_used(wch->wc_circ_size, wch->wc_head, wch->wc_tail);
  
          WAPBL_PRINTF(WAPBL_PRINT_REPLAY,
              ("wapbl_replay: head=%"PRId64" tail=%"PRId64" off=%"PRId64
              " len=%"PRId64" used=%zu\n",
              wch->wc_head, wch->wc_tail, wch->wc_circ_off,
              wch->wc_circ_size, used));
  
          wapbl_blkhash_init(wr, (used >> wch->wc_fs_dev_bshift));
  
          error = wapbl_replay_process(wr, wch->wc_head, wch->wc_tail);
          if (error) {
                  wapbl_replay_stop(wr);
                  wapbl_replay_free(wr);
                  return error;
          }
  
          *wrp = wr;
          return 0;
  
   errout:
          wapbl_free(scratch, MAXBSIZE);
          return error;
  }
  
  void
  wapbl_replay_stop(struct wapbl_replay *wr)
  {
  
          if (!wapbl_replay_isopen(wr))
                  return;
  
          WAPBL_PRINTF(WAPBL_PRINT_REPLAY, ("wapbl_replay_stop called\n"));
  
          wapbl_free(wr->wr_scratch, MAXBSIZE);
          wr->wr_scratch = NULL;
  
          wr->wr_logvp = NULL;
  
          wapbl_blkhash_clear(wr);
          wapbl_blkhash_free(wr);
  }
  
  void
  wapbl_replay_free(struct wapbl_replay *wr)
  {
  
          KDASSERT(!wapbl_replay_isopen(wr));
  
          if (wr->wr_inodes)
                  wapbl_free(wr->wr_inodes,
                      wr->wr_inodescnt * sizeof(wr->wr_inodes[0]));
          wapbl_free(wr, sizeof(*wr));
  }
  
  #ifdef _KERNEL
  int
  wapbl_replay_isopen1(struct wapbl_replay *wr)
  {
  
          return wapbl_replay_isopen(wr);
  }
  #endif
  
  /*
   * calculate the disk address for the i'th block in the wc_blockblist
   * offset by j blocks of size blen.
   *
   * wc_daddr is always a kernel disk address in DEV_BSIZE units that
   * was written to the journal.
   *
   * The kernel needs that address plus the offset in DEV_BSIZE units.
   *
   * Userland needs that address plus the offset in blen units.
   *
   */
  static daddr_t
  wapbl_block_daddr(struct wapbl_wc_blocklist *wc, int i, int j, int blen)
  {
          daddr_t pbn;
  
  #ifdef _KERNEL
          pbn = wc->wc_blocks[i].wc_daddr + btodb(j * blen);
  #else
          pbn = dbtob(wc->wc_blocks[i].wc_daddr) / blen + j;
  #endif
  
          return pbn;
  }
  
  static void
  wapbl_replay_process_blocks(struct wapbl_replay *wr, off_t *offp)
  {
          struct wapbl_wc_blocklist *wc =
              (struct wapbl_wc_blocklist *)wr->wr_scratch;
          int fsblklen = 1 << wr->wr_fs_dev_bshift;
          int i, j, n;
  
          for (i = 0; i < wc->wc_blkcount; i++) {
                  /*
                   * Enter each physical block into the hashtable independently.
                   */
                  n = wc->wc_blocks[i].wc_dlen >> wr->wr_fs_dev_bshift;
                  for (j = 0; j < n; j++) {
                          wapbl_blkhash_ins(wr, wapbl_block_daddr(wc, i, j, fsblklen),
                              *offp);
                          wapbl_circ_advance(wr, fsblklen, offp);
                  }
          }
  }
  
  static void
  wapbl_replay_process_revocations(struct wapbl_replay *wr)
  {
          struct wapbl_wc_blocklist *wc =
              (struct wapbl_wc_blocklist *)wr->wr_scratch;
          int fsblklen = 1 << wr->wr_fs_dev_bshift;
          int i, j, n;
  
          for (i = 0; i < wc->wc_blkcount; i++) {
                  /*
                   * Remove any blocks found from the hashtable.
                   */
                  n = wc->wc_blocks[i].wc_dlen >> wr->wr_fs_dev_bshift;
                  for (j = 0; j < n; j++)
                          wapbl_blkhash_rem(wr, wapbl_block_daddr(wc, i, j, fsblklen));
          }
  }
  
  static void
  wapbl_replay_process_inodes(struct wapbl_replay *wr, off_t oldoff, off_t newoff)
  {
          struct wapbl_wc_inodelist *wc =
              (struct wapbl_wc_inodelist *)wr->wr_scratch;
          void *new_inodes;
          const size_t oldsize = wr->wr_inodescnt * sizeof(wr->wr_inodes[0]);
  
          KASSERT(sizeof(wr->wr_inodes[0]) == sizeof(wc->wc_inodes[0]));
  
          /*
           * Keep track of where we found this so location won't be
           * overwritten.
           */
          if (wc->wc_clear) {
                  wr->wr_inodestail = oldoff;
                  wr->wr_inodescnt = 0;
                  if (wr->wr_inodes != NULL) {
                          wapbl_free(wr->wr_inodes, oldsize);
                          wr->wr_inodes = NULL;
                  }
          }
          wr->wr_inodeshead = newoff;
          if (wc->wc_inocnt == 0)
                  return;
  
          new_inodes = wapbl_alloc((wr->wr_inodescnt + wc->wc_inocnt) *
              sizeof(wr->wr_inodes[0]));
          if (wr->wr_inodes != NULL) {
                  memcpy(new_inodes, wr->wr_inodes, oldsize);
                  wapbl_free(wr->wr_inodes, oldsize);
          }
          wr->wr_inodes = new_inodes;
          memcpy(&wr->wr_inodes[wr->wr_inodescnt], wc->wc_inodes,
              wc->wc_inocnt * sizeof(wr->wr_inodes[0]));
          wr->wr_inodescnt += wc->wc_inocnt;
  }
  
  static int
  wapbl_replay_process(struct wapbl_replay *wr, off_t head, off_t tail)
  {
          off_t off;
          int error;
  
          int logblklen = 1 << wr->wr_log_dev_bshift;
  
          wapbl_blkhash_clear(wr);
  
          off = tail;
          while (off != head) {
                  struct wapbl_wc_null *wcn;
                  off_t saveoff = off;
                  error = wapbl_circ_read(wr, wr->wr_scratch, logblklen, &off);
                  if (error)
                          goto errout;
                  wcn = (struct wapbl_wc_null *)wr->wr_scratch;
                  switch (wcn->wc_type) {
                  case WAPBL_WC_BLOCKS:
                          wapbl_replay_process_blocks(wr, &off);
                          break;
  
                  case WAPBL_WC_REVOCATIONS:
                          wapbl_replay_process_revocations(wr);
                          break;
  
                  case WAPBL_WC_INODES:
                          wapbl_replay_process_inodes(wr, saveoff, off);
                          break;
  
                  default:
                          printf("Unrecognized wapbl type: 0x%08x\n",
                                 wcn->wc_type);
                          error = EFTYPE;
                          goto errout;
                  }
                  wapbl_circ_advance(wr, wcn->wc_len, &saveoff);
                  if (off != saveoff) {
                          printf("wapbl_replay: corrupted records\n");
                          error = EFTYPE;
                          goto errout;
                  }
          }
          return 0;
  
   errout:
          wapbl_blkhash_clear(wr);
          return error;
  }
  
  #if 0
  int
  wapbl_replay_verify(struct wapbl_replay *wr, struct vnode *fsdevvp)
  {
          off_t off;
          int mismatchcnt = 0;
          int logblklen = 1 << wr->wr_log_dev_bshift;
          int fsblklen = 1 << wr->wr_fs_dev_bshift;
          void *scratch1 = wapbl_alloc(MAXBSIZE);
          void *scratch2 = wapbl_alloc(MAXBSIZE);
          int error = 0;
  
          KDASSERT(wapbl_replay_isopen(wr));
  
          off = wch->wc_tail;
          while (off != wch->wc_head) {
                  struct wapbl_wc_null *wcn;
  #ifdef DEBUG
                  off_t saveoff = off;
  #endif
                  error = wapbl_circ_read(wr, wr->wr_scratch, logblklen, &off);
                  if (error)
                          goto out;
                  wcn = (struct wapbl_wc_null *)wr->wr_scratch;
                  switch (wcn->wc_type) {
                  case WAPBL_WC_BLOCKS:
                          {
                                  struct wapbl_wc_blocklist *wc =
                                      (struct wapbl_wc_blocklist *)wr->wr_scratch;
                                  int i;
                                  for (i = 0; i < wc->wc_blkcount; i++) {
                                          int foundcnt = 0;
                                          int dirtycnt = 0;
                                          int j, n;
                                          /*
                                           * Check each physical block into the
                                           * hashtable independently
                                           */
                                          n = wc->wc_blocks[i].wc_dlen >>
                                              wch->wc_fs_dev_bshift;
                                          for (j = 0; j < n; j++) {
                                                  struct wapbl_blk *wb =
                                                     wapbl_blkhash_get(wr,
                                                     wapbl_block_daddr(wc, i, j, fsblklen));
                                                  if (wb && (wb->wb_off == off)) {
                                                          foundcnt++;
                                                          error =
                                                              wapbl_circ_read(wr,
                                                              scratch1, fsblklen,
                                                              &off);
                                                          if (error)
                                                                  goto out;
                                                          error =
                                                              wapbl_read(scratch2,
                                                              fsblklen, fsdevvp,
                                                              wb->wb_blk);
                                                          if (error)
                                                                  goto out;
                                                          if (memcmp(scratch1,
                                                                     scratch2,
                                                                     fsblklen)) {
                                                                  printf(
                  "wapbl_verify: mismatch block %"PRId64" at off %"PRIdMAX"\n",
                  wb->wb_blk, (intmax_t)off);
                                                                  dirtycnt++;
                                                                  mismatchcnt++;
                                                          }
                                                  } else {
                                                          wapbl_circ_advance(wr,
                                                              fsblklen, &off);
                                                  }
                                          }
  #if 0
                                          /*
                                           * If all of the blocks in an entry
                                           * are clean, then remove all of its
                                           * blocks from the hashtable since they
                                           * never will need replay.
                                           */
                                          if ((foundcnt != 0) &&
                                              (dirtycnt == 0)) {
                                                  off = saveoff;
                                                  wapbl_circ_advance(wr,
                                                      logblklen, &off);
                                                  for (j = 0; j < n; j++) {
                                                          struct wapbl_blk *wb =
                                                             wapbl_blkhash_get(wr,
                                                             wapbl_block_daddr(wc, i, j, fsblklen));
                                                          if (wb &&
                                                            (wb->wb_off == off)) {
                                                                  wapbl_blkhash_rem(wr, wb->wb_blk);
                                                          }
                                                          wapbl_circ_advance(wr,
                                                              fsblklen, &off);
                                                  }
                                          }
  #endif
                                  }
                          }
                          break;
                  case WAPBL_WC_REVOCATIONS:
                  case WAPBL_WC_INODES:
                          break;
                  default:
                          KASSERT(0);
                  }
  #ifdef DEBUG
                  wapbl_circ_advance(wr, wcn->wc_len, &saveoff);
                  KASSERT(off == saveoff);
  #endif
          }
   out:
          wapbl_free(scratch1, MAXBSIZE);
          wapbl_free(scratch2, MAXBSIZE);
          if (!error && mismatchcnt)
                  error = EFTYPE;
          return error;
  }
  #endif
  
  int
  wapbl_replay_write(struct wapbl_replay *wr, struct vnode *fsdevvp)
  {
          struct wapbl_blk *wb;
          size_t i;
          off_t off;
          void *scratch;
          int error = 0;
          int fsblklen = 1 << wr->wr_fs_dev_bshift;
  
          KDASSERT(wapbl_replay_isopen(wr));
  
          scratch = wapbl_alloc(MAXBSIZE);
  
          for (i = 0; i <= wr->wr_blkhashmask; ++i) {
                  LIST_FOREACH(wb, &wr->wr_blkhash[i], wb_hash) {
                          off = wb->wb_off;
                          error = wapbl_circ_read(wr, scratch, fsblklen, &off);
                          if (error)
                                  break;
                          error = wapbl_write(scratch, fsblklen, fsdevvp,
                              wb->wb_blk);
                          if (error)
                                  break;
                  }
          }
  
          wapbl_free(scratch, MAXBSIZE);
          return error;
  }
  
  int
  wapbl_replay_can_read(struct wapbl_replay *wr, daddr_t blk, long len)
  {
          int fsblklen = 1 << wr->wr_fs_dev_bshift;
  
          KDASSERT(wapbl_replay_isopen(wr));
          KASSERT((len % fsblklen) == 0);
  
          while (len != 0) {
                  struct wapbl_blk *wb = wapbl_blkhash_get(wr, blk);
                  if (wb)
                          return 1;
                  len -= fsblklen;
          }
          return 0;
  }
  
  int
  wapbl_replay_read(struct wapbl_replay *wr, void *data, daddr_t blk, long len)
  {
          int fsblklen = 1 << wr->wr_fs_dev_bshift;
  
          KDASSERT(wapbl_replay_isopen(wr));
  
          KASSERT((len % fsblklen) == 0);
  
          while (len != 0) {
                  struct wapbl_blk *wb = wapbl_blkhash_get(wr, blk);
                  if (wb) {
                          off_t off = wb->wb_off;
                          int error;
                          error = wapbl_circ_read(wr, data, fsblklen, &off);
                          if (error)
                                  return error;
                  }
                  data = (uint8_t *)data + fsblklen;
                  len -= fsblklen;
                  blk++;
          }
          return 0;
  }
  
  #ifdef _KERNEL
  
  MODULE(MODULE_CLASS_VFS, wapbl, NULL);
  
  static int
  wapbl_modcmd(modcmd_t cmd, void *arg)
  {
  
          switch (cmd) {
          case MODULE_CMD_INIT:
                  wapbl_init();
                  return 0;
          case MODULE_CMD_FINI:
                  return wapbl_fini();
          default:
                  return ENOTTY;
          }
  }
  #endif /* _KERNEL */

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