FreeBSD/Linux Kernel Cross Reference
sys/fs/ext2fs/ext2_alloc.c

     /*-
      *  modified for Lites 1.1
      *
      *  Aug 1995, Godmar Back (gback@cs.utah.edu)
      *  University of Utah, Department of Computer Science
      */
     /*-
      * Copyright (c) 1982, 1986, 1989, 1993
      *      The Regents of the University of California.  All rights reserved.
     *
     * 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.
     * 4. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
     *
     *      @(#)ffs_alloc.c 8.8 (Berkeley) 2/21/94
     * $FreeBSD: releng/11.0/sys/fs/ext2fs/ext2_alloc.c 301548 2016-06-07 14:37:43Z pfg $
     */
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/conf.h>
    #include <sys/vnode.h>
    #include <sys/stat.h>
    #include <sys/mount.h>
    #include <sys/sysctl.h>
    #include <sys/syslog.h>
    #include <sys/buf.h>
    
    #include <fs/ext2fs/fs.h>
    #include <fs/ext2fs/inode.h>
    #include <fs/ext2fs/ext2_mount.h>
    #include <fs/ext2fs/ext2fs.h>
    #include <fs/ext2fs/ext2_extern.h>
    
    static daddr_t  ext2_alloccg(struct inode *, int, daddr_t, int);
    static daddr_t  ext2_clusteralloc(struct inode *, int, daddr_t, int);
    static u_long   ext2_dirpref(struct inode *);
    static void     ext2_fserr(struct m_ext2fs *, uid_t, char *);
    static u_long   ext2_hashalloc(struct inode *, int, long, int,
                                    daddr_t (*)(struct inode *, int, daddr_t, 
                                                    int));
    static daddr_t  ext2_nodealloccg(struct inode *, int, daddr_t, int);
    static daddr_t  ext2_mapsearch(struct m_ext2fs *, char *, daddr_t);
    
    /*
     * Allocate a block in the filesystem.
     *
     * A preference may be optionally specified. If a preference is given
     * the following hierarchy is used to allocate a block:
     *   1) allocate the requested block.
     *   2) allocate a rotationally optimal block in the same cylinder.
     *   3) allocate a block in the same cylinder group.
     *   4) quadradically rehash into other cylinder groups, until an
     *        available block is located.
     * If no block preference is given the following hierarchy is used
     * to allocate a block:
     *   1) allocate a block in the cylinder group that contains the
     *        inode for the file.
     *   2) quadradically rehash into other cylinder groups, until an
     *        available block is located.
     */
    int
    ext2_alloc(struct inode *ip, daddr_t lbn, e4fs_daddr_t bpref, int size,
        struct ucred *cred, e4fs_daddr_t *bnp)
    {
            struct m_ext2fs *fs;
            struct ext2mount *ump;
            int32_t bno;
            int cg; 
            *bnp = 0;
            fs = ip->i_e2fs;
            ump = ip->i_ump;
            mtx_assert(EXT2_MTX(ump), MA_OWNED);
    #ifdef INVARIANTS
            if ((u_int)size > fs->e2fs_bsize || blkoff(fs, size) != 0) {
                    vn_printf(ip->i_devvp, "bsize = %lu, size = %d, fs = %s\n",
                        (long unsigned int)fs->e2fs_bsize, size, fs->e2fs_fsmnt);
                    panic("ext2_alloc: bad size");
            }
           if (cred == NOCRED)
                   panic("ext2_alloc: missing credential");
   #endif /* INVARIANTS */
           if (size == fs->e2fs_bsize && fs->e2fs->e2fs_fbcount == 0)
                   goto nospace;
           if (cred->cr_uid != 0 && 
                   fs->e2fs->e2fs_fbcount < fs->e2fs->e2fs_rbcount)
                   goto nospace;
           if (bpref >= fs->e2fs->e2fs_bcount)
                   bpref = 0;
           if (bpref == 0)
                   cg = ino_to_cg(fs, ip->i_number);
           else
                   cg = dtog(fs, bpref);
           bno = (daddr_t)ext2_hashalloc(ip, cg, bpref, fs->e2fs_bsize,
                                         ext2_alloccg);
           if (bno > 0) {
                   /* set next_alloc fields as done in block_getblk */
                   ip->i_next_alloc_block = lbn;
                   ip->i_next_alloc_goal = bno;
   
                   ip->i_blocks += btodb(fs->e2fs_bsize);
                   ip->i_flag |= IN_CHANGE | IN_UPDATE;
                   *bnp = bno;
                   return (0);
           }
   nospace:
           EXT2_UNLOCK(ump);
           ext2_fserr(fs, cred->cr_uid, "filesystem full");
           uprintf("\n%s: write failed, filesystem is full\n", fs->e2fs_fsmnt);
           return (ENOSPC);
   }
   
   /*
    * Reallocate a sequence of blocks into a contiguous sequence of blocks.
    *
    * The vnode and an array of buffer pointers for a range of sequential
    * logical blocks to be made contiguous is given. The allocator attempts
    * to find a range of sequential blocks starting as close as possible to
    * an fs_rotdelay offset from the end of the allocation for the logical
    * block immediately preceding the current range. If successful, the
    * physical block numbers in the buffer pointers and in the inode are
    * changed to reflect the new allocation. If unsuccessful, the allocation
    * is left unchanged. The success in doing the reallocation is returned.
    * Note that the error return is not reflected back to the user. Rather
    * the previous block allocation will be used.
    */
   
   static SYSCTL_NODE(_vfs, OID_AUTO, ext2fs, CTLFLAG_RW, 0, "EXT2FS filesystem");
   
   static int doasyncfree = 1;
   SYSCTL_INT(_vfs_ext2fs, OID_AUTO, doasyncfree, CTLFLAG_RW, &doasyncfree, 0,
       "Use asychronous writes to update block pointers when freeing blocks");
   
   static int doreallocblks = 1;
   SYSCTL_INT(_vfs_ext2fs, OID_AUTO, doreallocblks, CTLFLAG_RW, &doreallocblks, 0, "");
   
   int
   ext2_reallocblks(struct vop_reallocblks_args *ap)
   {
           struct m_ext2fs *fs;
           struct inode *ip;
           struct vnode *vp;
           struct buf *sbp, *ebp;
           uint32_t *bap, *sbap, *ebap;
           struct ext2mount *ump;
           struct cluster_save *buflist;
           struct indir start_ap[NIADDR + 1], end_ap[NIADDR + 1], *idp;
           e2fs_lbn_t start_lbn, end_lbn;
           int soff;
           e2fs_daddr_t newblk, blkno;
           int i, len, start_lvl, end_lvl, pref, ssize;
   
           if (doreallocblks == 0)
                     return (ENOSPC);
   
           vp = ap->a_vp;
           ip = VTOI(vp);
           fs = ip->i_e2fs;
           ump = ip->i_ump;
   
           if (fs->e2fs_contigsumsize <= 0)
                   return (ENOSPC);
   
           buflist = ap->a_buflist;
           len = buflist->bs_nchildren;
           start_lbn = buflist->bs_children[0]->b_lblkno;
           end_lbn = start_lbn + len - 1;
   #ifdef INVARIANTS
           for (i = 1; i < len; i++)
                   if (buflist->bs_children[i]->b_lblkno != start_lbn + i)
                           panic("ext2_reallocblks: non-cluster");
   #endif
           /*
            * If the cluster crosses the boundary for the first indirect
            * block, leave space for the indirect block. Indirect blocks
            * are initially laid out in a position after the last direct
            * block. Block reallocation would usually destroy locality by
            * moving the indirect block out of the way to make room for
            * data blocks if we didn't compensate here. We should also do
            * this for other indirect block boundaries, but it is only
            * important for the first one.
            */
           if (start_lbn < NDADDR && end_lbn >= NDADDR)
                   return (ENOSPC);
           /*
            * If the latest allocation is in a new cylinder group, assume that
            * the filesystem has decided to move and do not force it back to
            * the previous cylinder group.
            */
           if (dtog(fs, dbtofsb(fs, buflist->bs_children[0]->b_blkno)) !=
               dtog(fs, dbtofsb(fs, buflist->bs_children[len - 1]->b_blkno)))
                   return (ENOSPC);
           if (ext2_getlbns(vp, start_lbn, start_ap, &start_lvl) ||
               ext2_getlbns(vp, end_lbn, end_ap, &end_lvl))
                   return (ENOSPC);
           /*
            * Get the starting offset and block map for the first block.
            */
           if (start_lvl == 0) {
                   sbap = &ip->i_db[0];
                   soff = start_lbn;
           } else {
                   idp = &start_ap[start_lvl - 1];
                   if (bread(vp, idp->in_lbn, (int)fs->e2fs_bsize, NOCRED, &sbp)) {
                           brelse(sbp);
                           return (ENOSPC);
                   }
                   sbap = (u_int *)sbp->b_data;
                   soff = idp->in_off;
           }
           /*
            * If the block range spans two block maps, get the second map.
            */
           ebap = NULL;
           if (end_lvl == 0 || (idp = &end_ap[end_lvl - 1])->in_off + 1 >= len) {
                   ssize = len;
           } else {
   #ifdef INVARIANTS
                   if (start_ap[start_lvl-1].in_lbn == idp->in_lbn)
                           panic("ext2_reallocblks: start == end");
   #endif
                   ssize = len - (idp->in_off + 1);
                   if (bread(vp, idp->in_lbn, (int)fs->e2fs_bsize, NOCRED, &ebp))
                           goto fail;
                   ebap = (u_int *)ebp->b_data;
           }
           /*
            * Find the preferred location for the cluster.
            */
           EXT2_LOCK(ump);
           pref = ext2_blkpref(ip, start_lbn, soff, sbap, 0);
           /*
            * Search the block map looking for an allocation of the desired size.
            */
           if ((newblk = (e2fs_daddr_t)ext2_hashalloc(ip, dtog(fs, pref), pref,
               len, ext2_clusteralloc)) == 0){
                   EXT2_UNLOCK(ump);
                   goto fail;
           }       
           /*
            * We have found a new contiguous block.
            *
            * First we have to replace the old block pointers with the new
            * block pointers in the inode and indirect blocks associated
            * with the file.
            */
   #ifdef DEBUG
           printf("realloc: ino %ju, lbns %jd-%jd\n\told:",
               (uintmax_t)ip->i_number, (intmax_t)start_lbn, (intmax_t)end_lbn);
   #endif /* DEBUG */
           blkno = newblk;
           for (bap = &sbap[soff], i = 0; i < len; i++, blkno += fs->e2fs_fpb) {
                   if (i == ssize) {
                           bap = ebap;
                           soff = -i;
                   }
   #ifdef INVARIANTS
                   if (buflist->bs_children[i]->b_blkno != fsbtodb(fs, *bap))
                           panic("ext2_reallocblks: alloc mismatch");
   #endif
   #ifdef DEBUG
           printf(" %d,", *bap);
   #endif /* DEBUG */
                   *bap++ = blkno;
           }
           /*
            * Next we must write out the modified inode and indirect blocks.
            * For strict correctness, the writes should be synchronous since
            * the old block values may have been written to disk. In practise
            * they are almost never written, but if we are concerned about 
            * strict correctness, the `doasyncfree' flag should be set to zero.
            *
            * The test on `doasyncfree' should be changed to test a flag
            * that shows whether the associated buffers and inodes have
            * been written. The flag should be set when the cluster is
            * started and cleared whenever the buffer or inode is flushed.
            * We can then check below to see if it is set, and do the
            * synchronous write only when it has been cleared.
            */
           if (sbap != &ip->i_db[0]) {
                   if (doasyncfree)
                           bdwrite(sbp);
                   else
                           bwrite(sbp);
           } else {
                   ip->i_flag |= IN_CHANGE | IN_UPDATE;
                   if (!doasyncfree)
                           ext2_update(vp, 1);
           }
           if (ssize < len) {
                   if (doasyncfree)
                           bdwrite(ebp);
                   else
                           bwrite(ebp);
           }
           /*
            * Last, free the old blocks and assign the new blocks to the buffers.
            */
   #ifdef DEBUG
           printf("\n\tnew:");
   #endif /* DEBUG */
           for (blkno = newblk, i = 0; i < len; i++, blkno += fs->e2fs_fpb) {
                   ext2_blkfree(ip, dbtofsb(fs, buflist->bs_children[i]->b_blkno),
                       fs->e2fs_bsize);
                   buflist->bs_children[i]->b_blkno = fsbtodb(fs, blkno);
   #ifdef DEBUG
                   printf(" %d,", blkno);
   #endif /* DEBUG */
           }
   #ifdef DEBUG
           printf("\n");
   #endif /* DEBUG */
           return (0);
   
   fail:
           if (ssize < len)
                   brelse(ebp);
           if (sbap != &ip->i_db[0])
                   brelse(sbp);
           return (ENOSPC);
   }
   
   /*
    * Allocate an inode in the filesystem.
    * 
    */
   int
   ext2_valloc(struct vnode *pvp, int mode, struct ucred *cred, struct vnode **vpp)
   {
           struct timespec ts;
           struct inode *pip;
           struct m_ext2fs *fs;
           struct inode *ip;
           struct ext2mount *ump;
           ino_t ino, ipref;
           int i, error, cg;
           
           *vpp = NULL;
           pip = VTOI(pvp);
           fs = pip->i_e2fs;
           ump = pip->i_ump;
   
           EXT2_LOCK(ump);
           if (fs->e2fs->e2fs_ficount == 0)
                   goto noinodes;
           /*
            * If it is a directory then obtain a cylinder group based on
            * ext2_dirpref else obtain it using ino_to_cg. The preferred inode is
            * always the next inode.
            */
           if ((mode & IFMT) == IFDIR) {
                   cg = ext2_dirpref(pip);
                   if (fs->e2fs_contigdirs[cg] < 255)
                           fs->e2fs_contigdirs[cg]++;
           } else {
                   cg = ino_to_cg(fs, pip->i_number);
                   if (fs->e2fs_contigdirs[cg] > 0)
                           fs->e2fs_contigdirs[cg]--;
           }
           ipref = cg * fs->e2fs->e2fs_ipg + 1;
           ino = (ino_t)ext2_hashalloc(pip, cg, (long)ipref, mode, ext2_nodealloccg);
   
           if (ino == 0) 
                   goto noinodes;
           error = VFS_VGET(pvp->v_mount, ino, LK_EXCLUSIVE, vpp);
           if (error) {
                   ext2_vfree(pvp, ino, mode);
                   return (error);
           }
           ip = VTOI(*vpp);
   
           /*
            * The question is whether using VGET was such good idea at all:
            * Linux doesn't read the old inode in when it is allocating a
            * new one. I will set at least i_size and i_blocks to zero.
            */
           ip->i_flag = 0;
           ip->i_size = 0;
           ip->i_blocks = 0;
           ip->i_mode = 0;
           ip->i_flags = 0;
           /* now we want to make sure that the block pointers are zeroed out */
           for (i = 0; i < NDADDR; i++)
                   ip->i_db[i] = 0;
           for (i = 0; i < NIADDR; i++)
                   ip->i_ib[i] = 0;
   
           /*
            * Set up a new generation number for this inode.
            * Avoid zero values.
            */
           do {
                   ip->i_gen = arc4random();
           } while ( ip->i_gen == 0);
   
           vfs_timestamp(&ts);
           ip->i_birthtime = ts.tv_sec;
           ip->i_birthnsec = ts.tv_nsec;
   
   /*
   printf("ext2_valloc: allocated inode %d\n", ino);
   */
           return (0);
   noinodes:
           EXT2_UNLOCK(ump);
           ext2_fserr(fs, cred->cr_uid, "out of inodes");
           uprintf("\n%s: create/symlink failed, no inodes free\n", fs->e2fs_fsmnt);
           return (ENOSPC);
   }
   
   /*
    * Find a cylinder to place a directory.
    *
    * The policy implemented by this algorithm is to allocate a
    * directory inode in the same cylinder group as its parent
    * directory, but also to reserve space for its files inodes
    * and data. Restrict the number of directories which may be
    * allocated one after another in the same cylinder group
    * without intervening allocation of files.
    *
    * If we allocate a first level directory then force allocation
    * in another cylinder group.
    *
    */
   static u_long
   ext2_dirpref(struct inode *pip)
   {
           struct m_ext2fs *fs;
           int cg, prefcg, cgsize;
           u_int avgifree, avgbfree, avgndir, curdirsize;
           u_int minifree, minbfree, maxndir;
           u_int mincg, minndir;
           u_int dirsize, maxcontigdirs;
   
           mtx_assert(EXT2_MTX(pip->i_ump), MA_OWNED);
           fs = pip->i_e2fs;
   
           avgifree = fs->e2fs->e2fs_ficount / fs->e2fs_gcount;
           avgbfree = fs->e2fs->e2fs_fbcount / fs->e2fs_gcount;
           avgndir  = fs->e2fs_total_dir / fs->e2fs_gcount;
   
           /*
            * Force allocation in another cg if creating a first level dir.
            */
           ASSERT_VOP_LOCKED(ITOV(pip), "ext2fs_dirpref");
           if (ITOV(pip)->v_vflag & VV_ROOT) {
                   prefcg = arc4random() % fs->e2fs_gcount;
                   mincg = prefcg;
                   minndir = fs->e2fs_ipg;
                   for (cg = prefcg; cg < fs->e2fs_gcount; cg++)
                           if (fs->e2fs_gd[cg].ext2bgd_ndirs < minndir &&
                               fs->e2fs_gd[cg].ext2bgd_nifree >= avgifree &&
                               fs->e2fs_gd[cg].ext2bgd_nbfree >= avgbfree) {
                                   mincg = cg;
                                   minndir = fs->e2fs_gd[cg].ext2bgd_ndirs;
                           }
                   for (cg = 0; cg < prefcg; cg++)
                           if (fs->e2fs_gd[cg].ext2bgd_ndirs < minndir &&
                               fs->e2fs_gd[cg].ext2bgd_nifree >= avgifree &&
                               fs->e2fs_gd[cg].ext2bgd_nbfree >= avgbfree) {
                                   mincg = cg;
                                   minndir = fs->e2fs_gd[cg].ext2bgd_ndirs;
                           }
   
                   return (mincg);
           }
   
           /*
            * Count various limits which used for
            * optimal allocation of a directory inode.
            */
           maxndir = min(avgndir + fs->e2fs_ipg / 16, fs->e2fs_ipg);
           minifree = avgifree - avgifree / 4;
           if (minifree < 1)
                   minifree = 1;
           minbfree = avgbfree - avgbfree / 4;
           if (minbfree < 1)
                   minbfree = 1;
           cgsize = fs->e2fs_fsize * fs->e2fs_fpg;
           dirsize = AVGDIRSIZE;
           curdirsize = avgndir ? (cgsize - avgbfree * fs->e2fs_bsize) / avgndir : 0;
           if (dirsize < curdirsize)
                   dirsize = curdirsize;
           maxcontigdirs = min((avgbfree * fs->e2fs_bsize) / dirsize, 255);
           maxcontigdirs = min(maxcontigdirs, fs->e2fs_ipg / AFPDIR);
           if (maxcontigdirs == 0)
                   maxcontigdirs = 1;
   
           /*
            * Limit number of dirs in one cg and reserve space for 
            * regular files, but only if we have no deficit in
            * inodes or space.
            */
           prefcg = ino_to_cg(fs, pip->i_number);
           for (cg = prefcg; cg < fs->e2fs_gcount; cg++)
                   if (fs->e2fs_gd[cg].ext2bgd_ndirs < maxndir &&
                       fs->e2fs_gd[cg].ext2bgd_nifree >= minifree &&
                       fs->e2fs_gd[cg].ext2bgd_nbfree >= minbfree) {
                           if (fs->e2fs_contigdirs[cg] < maxcontigdirs)
                                   return (cg);
                   }
           for (cg = 0; cg < prefcg; cg++)
                   if (fs->e2fs_gd[cg].ext2bgd_ndirs < maxndir &&
                       fs->e2fs_gd[cg].ext2bgd_nifree >= minifree &&
                       fs->e2fs_gd[cg].ext2bgd_nbfree >= minbfree) {
                           if (fs->e2fs_contigdirs[cg] < maxcontigdirs)
                                   return (cg);
                   }
           /*
            * This is a backstop when we have deficit in space.
            */
           for (cg = prefcg; cg < fs->e2fs_gcount; cg++)
                   if (fs->e2fs_gd[cg].ext2bgd_nifree >= avgifree)
                           return (cg);
           for (cg = 0; cg < prefcg; cg++)
                   if (fs->e2fs_gd[cg].ext2bgd_nifree >= avgifree)
                           break;
           return (cg);
   }
   
   /*
    * Select the desired position for the next block in a file.  
    *
    * we try to mimic what Remy does in inode_getblk/block_getblk
    *
    * we note: blocknr == 0 means that we're about to allocate either
    * a direct block or a pointer block at the first level of indirection
    * (In other words, stuff that will go in i_db[] or i_ib[])
    *
    * blocknr != 0 means that we're allocating a block that is none
    * of the above. Then, blocknr tells us the number of the block
    * that will hold the pointer
    */
   e4fs_daddr_t
   ext2_blkpref(struct inode *ip, e2fs_lbn_t lbn, int indx, e2fs_daddr_t *bap,
       e2fs_daddr_t blocknr)
   {
           int     tmp;
           mtx_assert(EXT2_MTX(ip->i_ump), MA_OWNED);
   
           /* if the next block is actually what we thought it is,
              then set the goal to what we thought it should be
           */
           if (ip->i_next_alloc_block == lbn && ip->i_next_alloc_goal != 0)
                   return ip->i_next_alloc_goal;
   
           /* now check whether we were provided with an array that basically
              tells us previous blocks to which we want to stay closeby
           */
           if (bap)
                   for (tmp = indx - 1; tmp >= 0; tmp--) 
                           if (bap[tmp]) 
                                   return bap[tmp];
   
           /* else let's fall back to the blocknr, or, if there is none,
              follow the rule that a block should be allocated near its inode
           */
           return blocknr ? blocknr :
                           (e2fs_daddr_t)(ip->i_block_group * 
                           EXT2_BLOCKS_PER_GROUP(ip->i_e2fs)) + 
                           ip->i_e2fs->e2fs->e2fs_first_dblock;
   }
   
   /*
    * Implement the cylinder overflow algorithm.
    *
    * The policy implemented by this algorithm is:
    *   1) allocate the block in its requested cylinder group.
    *   2) quadradically rehash on the cylinder group number.
    *   3) brute force search for a free block.
    */
   static u_long
   ext2_hashalloc(struct inode *ip, int cg, long pref, int size,
                   daddr_t (*allocator)(struct inode *, int, daddr_t, int))
   {
           struct m_ext2fs *fs;
           ino_t result;
           int i, icg = cg;
   
           mtx_assert(EXT2_MTX(ip->i_ump), MA_OWNED);
           fs = ip->i_e2fs;
           /*
            * 1: preferred cylinder group
            */
           result = (*allocator)(ip, cg, pref, size);
           if (result)
                   return (result);
           /*
            * 2: quadratic rehash
            */
           for (i = 1; i < fs->e2fs_gcount; i *= 2) {
                   cg += i;
                   if (cg >= fs->e2fs_gcount)
                           cg -= fs->e2fs_gcount;
                   result = (*allocator)(ip, cg, 0, size);
                   if (result)
                           return (result);
           }
           /*
            * 3: brute force search
            * Note that we start at i == 2, since 0 was checked initially,
            * and 1 is always checked in the quadratic rehash.
            */
           cg = (icg + 2) % fs->e2fs_gcount;
           for (i = 2; i < fs->e2fs_gcount; i++) {
                   result = (*allocator)(ip, cg, 0, size);
                   if (result)
                           return (result);
                   cg++;
                   if (cg == fs->e2fs_gcount)
                           cg = 0;
           }
           return (0);
   }
   
   /*
    * Determine whether a block can be allocated.
    *
    * Check to see if a block of the appropriate size is available,
    * and if it is, allocate it.
    */
   static daddr_t
   ext2_alloccg(struct inode *ip, int cg, daddr_t bpref, int size)
   {
           struct m_ext2fs *fs;
           struct buf *bp;
           struct ext2mount *ump;
           daddr_t bno, runstart, runlen;
           int bit, loc, end, error, start;
           char *bbp;
           /* XXX ondisk32 */
           fs = ip->i_e2fs;
           ump = ip->i_ump;
           if (fs->e2fs_gd[cg].ext2bgd_nbfree == 0)
                   return (0);
           EXT2_UNLOCK(ump);
           error = bread(ip->i_devvp, fsbtodb(fs,
                   fs->e2fs_gd[cg].ext2bgd_b_bitmap),
                   (int)fs->e2fs_bsize, NOCRED, &bp);
           if (error) {
                   brelse(bp);
                   EXT2_LOCK(ump);
                   return (0);
           }
           if (fs->e2fs_gd[cg].ext2bgd_nbfree == 0) {
                   /*
                    * Another thread allocated the last block in this
                    * group while we were waiting for the buffer.
                    */
                   brelse(bp);
                   EXT2_LOCK(ump);
                   return (0);
           }
           bbp = (char *)bp->b_data;
   
           if (dtog(fs, bpref) != cg)
                   bpref = 0;
           if (bpref != 0) {
                   bpref = dtogd(fs, bpref);
                   /*
                    * if the requested block is available, use it
                    */
                   if (isclr(bbp, bpref)) {
                           bno = bpref;
                           goto gotit;
                   }
           }
           /*
            * no blocks in the requested cylinder, so take next
            * available one in this cylinder group.
            * first try to get 8 contigous blocks, then fall back to a single
            * block.
            */
           if (bpref)
                   start = dtogd(fs, bpref) / NBBY;
           else
                   start = 0;
           end = howmany(fs->e2fs->e2fs_fpg, NBBY) - start;
   retry:
           runlen = 0;
           runstart = 0;
           for (loc = start; loc < end; loc++) {
                   if (bbp[loc] == (char)0xff) {
                           runlen = 0;
                           continue;
                   }
   
                   /* Start of a run, find the number of high clear bits. */
                   if (runlen == 0) {
                           bit = fls(bbp[loc]);
                           runlen = NBBY - bit;
                           runstart = loc * NBBY + bit;
                   } else if (bbp[loc] == 0) {
                           /* Continue a run. */
                           runlen += NBBY;
                   } else {
                           /*
                            * Finish the current run.  If it isn't long
                            * enough, start a new one.
                            */
                           bit = ffs(bbp[loc]) - 1;
                           runlen += bit;
                           if (runlen >= 8) {
                                   bno = runstart;
                                   goto gotit;
                           }
   
                           /* Run was too short, start a new one. */
                           bit = fls(bbp[loc]);
                           runlen = NBBY - bit;
                           runstart = loc * NBBY + bit;
                   }
   
                   /* If the current run is long enough, use it. */
                   if (runlen >= 8) {
                           bno = runstart;
                           goto gotit;
                   }
           }
           if (start != 0) {
                   end = start;
                   start = 0;
                   goto retry;
           }
   
           bno = ext2_mapsearch(fs, bbp, bpref);
           if (bno < 0){
                   brelse(bp);
                   EXT2_LOCK(ump);
                   return (0);
           }
   gotit:
   #ifdef INVARIANTS
           if (isset(bbp, bno)) {
                   printf("ext2fs_alloccgblk: cg=%d bno=%jd fs=%s\n",
                           cg, (intmax_t)bno, fs->e2fs_fsmnt);
                   panic("ext2fs_alloccg: dup alloc");
           }
   #endif
           setbit(bbp, bno);
           EXT2_LOCK(ump);
           ext2_clusteracct(fs, bbp, cg, bno, -1);
           fs->e2fs->e2fs_fbcount--;
           fs->e2fs_gd[cg].ext2bgd_nbfree--;
           fs->e2fs_fmod = 1;
           EXT2_UNLOCK(ump);
           bdwrite(bp);
           return (cg * fs->e2fs->e2fs_fpg + fs->e2fs->e2fs_first_dblock + bno);
   }
   
   /*
    * Determine whether a cluster can be allocated.
    */
   static daddr_t
   ext2_clusteralloc(struct inode *ip, int cg, daddr_t bpref, int len)
   {
           struct m_ext2fs *fs;
           struct ext2mount *ump;
           struct buf *bp;
           char *bbp;
           int bit, error, got, i, loc, run;
           int32_t *lp;
           daddr_t bno;
   
           fs = ip->i_e2fs;
           ump = ip->i_ump;
   
           if (fs->e2fs_maxcluster[cg] < len)
                   return (0);
   
           EXT2_UNLOCK(ump);
           error = bread(ip->i_devvp,
               fsbtodb(fs, fs->e2fs_gd[cg].ext2bgd_b_bitmap),
               (int)fs->e2fs_bsize, NOCRED, &bp);
           if (error)
                   goto fail_lock;
   
           bbp = (char *)bp->b_data;
           EXT2_LOCK(ump);
           /*
            * Check to see if a cluster of the needed size (or bigger) is
            * available in this cylinder group.
            */
           lp = &fs->e2fs_clustersum[cg].cs_sum[len];
           for (i = len; i <= fs->e2fs_contigsumsize; i++)
                   if (*lp++ > 0)
                           break;
           if (i > fs->e2fs_contigsumsize) {
                   /*
                    * Update the cluster summary information to reflect
                    * the true maximum-sized cluster so that future cluster
                    * allocation requests can avoid reading the bitmap only
                    * to find no cluster.
                    */
                   lp = &fs->e2fs_clustersum[cg].cs_sum[len - 1];
                           for (i = len - 1; i > 0; i--)
                                   if (*lp-- > 0)
                                           break;
                   fs->e2fs_maxcluster[cg] = i;
                   goto fail;
           }
           EXT2_UNLOCK(ump);
   
           /* Search the bitmap to find a big enough cluster like in FFS. */
           if (dtog(fs, bpref) != cg)
                   bpref = 0;
           if (bpref != 0)
                   bpref = dtogd(fs, bpref);
           loc = bpref / NBBY;
           bit = 1 << (bpref % NBBY);
           for (run = 0, got = bpref; got < fs->e2fs->e2fs_fpg; got++) {
                   if ((bbp[loc] & bit) != 0)
                           run = 0;
                   else {
                           run++;
                           if (run == len)
                                   break;
                   }
                   if ((got & (NBBY - 1)) != (NBBY - 1))
                           bit <<= 1;
                   else {
                           loc++;
                           bit = 1;
                   }
           }
   
           if (got >= fs->e2fs->e2fs_fpg)
                   goto fail_lock;
   
           /* Allocate the cluster that we found. */
           for (i = 1; i < len; i++)
                   if (!isclr(bbp, got - run + i))
                           panic("ext2_clusteralloc: map mismatch");
   
           bno = got - run + 1;
           if (bno >= fs->e2fs->e2fs_fpg)
                   panic("ext2_clusteralloc: allocated out of group");
   
           EXT2_LOCK(ump);
           for (i = 0; i < len; i += fs->e2fs_fpb) {
                   setbit(bbp, bno + i);
                   ext2_clusteracct(fs, bbp, cg, bno + i, -1);
                   fs->e2fs->e2fs_fbcount--;
                   fs->e2fs_gd[cg].ext2bgd_nbfree--;
           }
           fs->e2fs_fmod = 1;
           EXT2_UNLOCK(ump);
   
           bdwrite(bp);
           return (cg * fs->e2fs->e2fs_fpg + fs->e2fs->e2fs_first_dblock + bno);
   
   fail_lock:
           EXT2_LOCK(ump);
   fail:
           brelse(bp);
           return (0);
   }
   
   /*
    * Determine whether an inode can be allocated.
    *
    * Check to see if an inode is available, and if it is,
    * allocate it using tode in the specified cylinder group.
    */
   static daddr_t
   ext2_nodealloccg(struct inode *ip, int cg, daddr_t ipref, int mode)
   {
           struct m_ext2fs *fs;
           struct buf *bp;
           struct ext2mount *ump;
           int error, start, len;
           char *ibp, *loc;
           ipref--; /* to avoid a lot of (ipref -1) */
           if (ipref == -1)
                   ipref = 0;
           fs = ip->i_e2fs;
           ump = ip->i_ump;
           if (fs->e2fs_gd[cg].ext2bgd_nifree == 0)
                   return (0);
           EXT2_UNLOCK(ump);       
           error = bread(ip->i_devvp, fsbtodb(fs,
                   fs->e2fs_gd[cg].ext2bgd_i_bitmap),
                   (int)fs->e2fs_bsize, NOCRED, &bp);
           if (error) {
                   brelse(bp);
                   EXT2_LOCK(ump);
                   return (0);
           }
           if (fs->e2fs_gd[cg].ext2bgd_nifree == 0) {
                   /*
                    * Another thread allocated the last i-node in this
                    * group while we were waiting for the buffer.
                    */
                   brelse(bp);
                   EXT2_LOCK(ump);
                   return (0);
           }
           ibp = (char *)bp->b_data;
           if (ipref) {
                   ipref %= fs->e2fs->e2fs_ipg;
                   if (isclr(ibp, ipref))
                           goto gotit;
           }
           start = ipref / NBBY;
           len = howmany(fs->e2fs->e2fs_ipg - ipref, NBBY);
           loc = memcchr(&ibp[start], 0xff, len);
           if (loc == NULL) {
                   len = start + 1;
                   start = 0;
                   loc = memcchr(&ibp[start], 0xff, len);
                   if (loc == NULL) {
                           printf("cg = %d, ipref = %lld, fs = %s\n",
                                   cg, (long long)ipref, fs->e2fs_fsmnt);
                           panic("ext2fs_nodealloccg: map corrupted");
                           /* NOTREACHED */
                   }
           }
           ipref = (loc - ibp) * NBBY + ffs(~*loc) - 1;
   gotit:
           setbit(ibp, ipref);
           EXT2_LOCK(ump);
           fs->e2fs_gd[cg].ext2bgd_nifree--;
           fs->e2fs->e2fs_ficount--;
           fs->e2fs_fmod = 1;
           if ((mode & IFMT) == IFDIR) {
                   fs->e2fs_gd[cg].ext2bgd_ndirs++;
                   fs->e2fs_total_dir++;
           }
           EXT2_UNLOCK(ump);
           bdwrite(bp);
           return (cg * fs->e2fs->e2fs_ipg + ipref +1);
   }
   
   /*
    * Free a block or fragment.
    *
    */
   void
   ext2_blkfree(struct inode *ip, e4fs_daddr_t bno, long size)
   {
           struct m_ext2fs *fs;
           struct buf *bp;
           struct ext2mount *ump;
           int cg, error;
           char *bbp;
   
           fs = ip->i_e2fs;
           ump = ip->i_ump;
           cg = dtog(fs, bno);
           if ((u_int)bno >= fs->e2fs->e2fs_bcount) {
                   printf("bad block %lld, ino %ju\n", (long long)bno,
                       (uintmax_t)ip->i_number);
                   ext2_fserr(fs, ip->i_uid, "bad block");
                   return;
           }
           error = bread(ip->i_devvp,
                   fsbtodb(fs, fs->e2fs_gd[cg].ext2bgd_b_bitmap),
                   (int)fs->e2fs_bsize, NOCRED, &bp);
           if (error) {
                   brelse(bp);
                   return;
           }
           bbp = (char *)bp->b_data;
           bno = dtogd(fs, bno);
           if (isclr(bbp, bno)) {
                   printf("block = %lld, fs = %s\n",
                        (long long)bno, fs->e2fs_fsmnt);
                   panic("ext2_blkfree: freeing free block");
           }
           clrbit(bbp, bno);
           EXT2_LOCK(ump);
           ext2_clusteracct(fs, bbp, cg, bno, 1);
           fs->e2fs->e2fs_fbcount++;
           fs->e2fs_gd[cg].ext2bgd_nbfree++;
           fs->e2fs_fmod = 1;
           EXT2_UNLOCK(ump);
           bdwrite(bp);
   }
   
  /*
   * Free an inode.
   *
   */
  int
  ext2_vfree(struct vnode *pvp, ino_t ino, int mode)
  {
          struct m_ext2fs *fs;
          struct inode *pip;
          struct buf *bp;
          struct ext2mount *ump;
          int error, cg;
          char * ibp;
  
          pip = VTOI(pvp);
          fs = pip->i_e2fs;
          ump = pip->i_ump;
          if ((u_int)ino > fs->e2fs_ipg * fs->e2fs_gcount)
                  panic("ext2_vfree: range: devvp = %p, ino = %ju, fs = %s",
                      pip->i_devvp, (uintmax_t)ino, fs->e2fs_fsmnt);
  
          cg = ino_to_cg(fs, ino);
          error = bread(pip->i_devvp,
                  fsbtodb(fs, fs->e2fs_gd[cg].ext2bgd_i_bitmap),
                  (int)fs->e2fs_bsize, NOCRED, &bp);
          if (error) {
                  brelse(bp);
                  return (0);
          }
          ibp = (char *)bp->b_data;
          ino = (ino - 1) % fs->e2fs->e2fs_ipg;
          if (isclr(ibp, ino)) {
                  printf("ino = %llu, fs = %s\n",
                           (unsigned long long)ino, fs->e2fs_fsmnt);
                  if (fs->e2fs_ronly == 0)
                          panic("ext2_vfree: freeing free inode");
          }
          clrbit(ibp, ino);
          EXT2_LOCK(ump);
          fs->e2fs->e2fs_ficount++;
          fs->e2fs_gd[cg].ext2bgd_nifree++;
          if ((mode & IFMT) == IFDIR) {
                  fs->e2fs_gd[cg].ext2bgd_ndirs--;
                  fs->e2fs_total_dir--;
          }
          fs->e2fs_fmod = 1;
          EXT2_UNLOCK(ump);
          bdwrite(bp);
          return (0);
  }
  
  /*
   * Find a block in the specified cylinder group.
   *
   * It is a panic if a request is made to find a block if none are
   * available.
   */
  static daddr_t
  ext2_mapsearch(struct m_ext2fs *fs, char *bbp, daddr_t bpref)
  {
          char *loc;
          int start, len;
  
          /*
           * find the fragment by searching through the free block
           * map for an appropriate bit pattern
           */
          if (bpref)
                  start = dtogd(fs, bpref) / NBBY;
          else
                  start = 0;
          len = howmany(fs->e2fs->e2fs_fpg, NBBY) - start;
          loc = memcchr(&bbp[start], 0xff, len);
          if (loc == NULL) {
                  len = start + 1;
                  start = 0;
                  loc = memcchr(&bbp[start], 0xff, len);
                  if (loc == NULL) {
                          printf("start = %d, len = %d, fs = %s\n",
                                  start, len, fs->e2fs_fsmnt);
                          panic("ext2_mapsearch: map corrupted");
                          /* NOTREACHED */
                  }
          }
          return ((loc - bbp) * NBBY + ffs(~*loc) - 1);
  }
  
  /*
   * Fserr prints the name of a filesystem with an error diagnostic.
   * 
   * The form of the error message is:
   *      fs: error message
   */
  static void
  ext2_fserr(struct m_ext2fs *fs, uid_t uid, char *cp)
  {
  
          log(LOG_ERR, "uid %u on %s: %s\n", uid, fs->e2fs_fsmnt, cp);
  }
  
  int
  cg_has_sb(int i)
  {
          int a3, a5, a7;
  
          if (i == 0 || i == 1)
                  return 1;
          for (a3 = 3, a5 = 5, a7 = 7;
              a3 <= i || a5 <= i || a7 <= i;
              a3 *= 3, a5 *= 5, a7 *= 7)
                  if (i == a3 || i == a5 || i == a7)
                          return 1;
          return 0;
  }

Cache object: 27d9468132e186912454029c154df6c9