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ffs_balloc.c

/*-
 * Copyright (c) 2002 Networks Associates Technology, Inc.
 * All rights reserved.
 *
 * This software was developed for the FreeBSD Project by Marshall
 * Kirk McKusick and Network Associates Laboratories, the Security
 * Research Division of Network Associates, Inc. under DARPA/SPAWAR
 * contract N66001-01-C-8035 ("CBOSS"), as part of the DARPA CHATS
 * research program
 *
 * 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 AUTHOR 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 AUTHOR 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.
 *
 * 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_balloc.c  8.8 (Berkeley) 6/16/95
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD: src/sys/ufs/ffs/ffs_balloc.c,v 1.50.14.1 2008/01/19 18:12:25 kib Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bio.h>
#include <sys/buf.h>
#include <sys/lock.h>
#include <sys/mount.h>
#include <sys/vnode.h>

#include <ufs/ufs/quota.h>
#include <ufs/ufs/inode.h>
#include <ufs/ufs/ufs_extern.h>
#include <ufs/ufs/extattr.h>
#include <ufs/ufs/ufsmount.h>

#include <ufs/ffs/fs.h>
#include <ufs/ffs/ffs_extern.h>

/*
 * Balloc defines the structure of filesystem storage
 * by allocating the physical blocks on a device given
 * the inode and the logical block number in a file.
 * This is the allocation strategy for UFS1. Below is
 * the allocation strategy for UFS2.
 */
int
ffs_balloc_ufs1(struct vnode *vp, off_t startoffset, int size,
    struct ucred *cred, int flags, struct buf **bpp)
{
      struct inode *ip;
      struct ufs1_dinode *dp;
      ufs_lbn_t lbn, lastlbn;
      struct fs *fs;
      ufs1_daddr_t nb;
      struct buf *bp, *nbp;
      struct ufsmount *ump;
      struct indir indirs[NIADDR + 2];
      int deallocated, osize, nsize, num, i, error;
      ufs2_daddr_t newb;
      ufs1_daddr_t *bap, pref;
      ufs1_daddr_t *allocib, *blkp, *allocblk, allociblk[NIADDR + 1];
      ufs2_daddr_t *lbns_remfree, lbns[NIADDR + 1];
      int unwindidx = -1;

      ip = VTOI(vp);
      dp = ip->i_din1;
      fs = ip->i_fs;
      ump = ip->i_ump;
      lbn = lblkno(fs, startoffset);
      size = blkoff(fs, startoffset) + size;
      if (size > fs->fs_bsize)
            panic("ffs_balloc_ufs1: blk too big");
      *bpp = NULL;
      if (flags & IO_EXT)
            return (EOPNOTSUPP);
      if (lbn < 0)
            return (EFBIG);

      /*
       * If the next write will extend the file into a new block,
       * and the file is currently composed of a fragment
       * this fragment has to be extended to be a full block.
       */
      lastlbn = lblkno(fs, ip->i_size);
      if (lastlbn < NDADDR && lastlbn < lbn) {
            nb = lastlbn;
            osize = blksize(fs, ip, nb);
            if (osize < fs->fs_bsize && osize > 0) {
                  UFS_LOCK(ump);
                  error = ffs_realloccg(ip, nb, dp->di_db[nb],
                     ffs_blkpref_ufs1(ip, lastlbn, (int)nb,
                     &dp->di_db[0]), osize, (int)fs->fs_bsize, cred, &bp);
                  if (error)
                        return (error);
                  if (DOINGSOFTDEP(vp))
                        softdep_setup_allocdirect(ip, nb,
                            dbtofsb(fs, bp->b_blkno), dp->di_db[nb],
                            fs->fs_bsize, osize, bp);
                  ip->i_size = smalllblktosize(fs, nb + 1);
                  dp->di_size = ip->i_size;
                  dp->di_db[nb] = dbtofsb(fs, bp->b_blkno);
                  ip->i_flag |= IN_CHANGE | IN_UPDATE;
                  if (flags & IO_SYNC)
                        bwrite(bp);
                  else
                        bawrite(bp);
            }
      }
      /*
       * The first NDADDR blocks are direct blocks
       */
      if (lbn < NDADDR) {
            if (flags & BA_METAONLY)
                  panic("ffs_balloc_ufs1: BA_METAONLY for direct block");
            nb = dp->di_db[lbn];
            if (nb != 0 && ip->i_size >= smalllblktosize(fs, lbn + 1)) {
                  error = bread(vp, lbn, fs->fs_bsize, NOCRED, &bp);
                  if (error) {
                        brelse(bp);
                        return (error);
                  }
                  bp->b_blkno = fsbtodb(fs, nb);
                  *bpp = bp;
                  return (0);
            }
            if (nb != 0) {
                  /*
                   * Consider need to reallocate a fragment.
                   */
                  osize = fragroundup(fs, blkoff(fs, ip->i_size));
                  nsize = fragroundup(fs, size);
                  if (nsize <= osize) {
                        error = bread(vp, lbn, osize, NOCRED, &bp);
                        if (error) {
                              brelse(bp);
                              return (error);
                        }
                        bp->b_blkno = fsbtodb(fs, nb);
                  } else {
                        UFS_LOCK(ump);
                        error = ffs_realloccg(ip, lbn, dp->di_db[lbn],
                            ffs_blkpref_ufs1(ip, lbn, (int)lbn,
                            &dp->di_db[0]), osize, nsize, cred, &bp);
                        if (error)
                              return (error);
                        if (DOINGSOFTDEP(vp))
                              softdep_setup_allocdirect(ip, lbn,
                                  dbtofsb(fs, bp->b_blkno), nb,
                                  nsize, osize, bp);
                  }
            } else {
                  if (ip->i_size < smalllblktosize(fs, lbn + 1))
                        nsize = fragroundup(fs, size);
                  else
                        nsize = fs->fs_bsize;
                  UFS_LOCK(ump);
                  error = ffs_alloc(ip, lbn,
                      ffs_blkpref_ufs1(ip, lbn, (int)lbn, &dp->di_db[0]),
                      nsize, cred, &newb);
                  if (error)
                        return (error);
                  bp = getblk(vp, lbn, nsize, 0, 0, 0);
                  bp->b_blkno = fsbtodb(fs, newb);
                  if (flags & BA_CLRBUF)
                        vfs_bio_clrbuf(bp);
                  if (DOINGSOFTDEP(vp))
                        softdep_setup_allocdirect(ip, lbn, newb, 0,
                            nsize, 0, bp);
            }
            dp->di_db[lbn] = dbtofsb(fs, bp->b_blkno);
            ip->i_flag |= IN_CHANGE | IN_UPDATE;
            *bpp = bp;
            return (0);
      }
      /*
       * Determine the number of levels of indirection.
       */
      pref = 0;
      if ((error = ufs_getlbns(vp, lbn, indirs, &num)) != 0)
            return(error);
#ifdef DIAGNOSTIC
      if (num < 1)
            panic ("ffs_balloc_ufs1: ufs_getlbns returned indirect block");
#endif
      /*
       * Fetch the first indirect block allocating if necessary.
       */
      --num;
      nb = dp->di_ib[indirs[0].in_off];
      allocib = NULL;
      allocblk = allociblk;
      lbns_remfree = lbns;
      if (nb == 0) {
            UFS_LOCK(ump);
            pref = ffs_blkpref_ufs1(ip, lbn, 0, (ufs1_daddr_t *)0);
              if ((error = ffs_alloc(ip, lbn, pref, (int)fs->fs_bsize,
                cred, &newb)) != 0)
                  return (error);
            nb = newb;
            *allocblk++ = nb;
            *lbns_remfree++ = indirs[1].in_lbn;
            bp = getblk(vp, indirs[1].in_lbn, fs->fs_bsize, 0, 0, 0);
            bp->b_blkno = fsbtodb(fs, nb);
            vfs_bio_clrbuf(bp);
            if (DOINGSOFTDEP(vp)) {
                  softdep_setup_allocdirect(ip, NDADDR + indirs[0].in_off,
                      newb, 0, fs->fs_bsize, 0, bp);
                  bdwrite(bp);
            } else {
                  /*
                   * Write synchronously so that indirect blocks
                   * never point at garbage.
                   */
                  if (DOINGASYNC(vp))
                        bdwrite(bp);
                  else if ((error = bwrite(bp)) != 0)
                        goto fail;
            }
            allocib = &dp->di_ib[indirs[0].in_off];
            *allocib = nb;
            ip->i_flag |= IN_CHANGE | IN_UPDATE;
      }
      /*
       * Fetch through the indirect blocks, allocating as necessary.
       */
      for (i = 1;;) {
            error = bread(vp,
                indirs[i].in_lbn, (int)fs->fs_bsize, NOCRED, &bp);
            if (error) {
                  brelse(bp);
                  goto fail;
            }
            bap = (ufs1_daddr_t *)bp->b_data;
            nb = bap[indirs[i].in_off];
            if (i == num)
                  break;
            i += 1;
            if (nb != 0) {
                  bqrelse(bp);
                  continue;
            }
            UFS_LOCK(ump);
            if (pref == 0)
                  pref = ffs_blkpref_ufs1(ip, lbn, 0, (ufs1_daddr_t *)0);
            if ((error =
                ffs_alloc(ip, lbn, pref, (int)fs->fs_bsize, cred, &newb)) != 0) {
                  brelse(bp);
                  goto fail;
            }
            nb = newb;
            *allocblk++ = nb;
            *lbns_remfree++ = indirs[i].in_lbn;
            nbp = getblk(vp, indirs[i].in_lbn, fs->fs_bsize, 0, 0, 0);
            nbp->b_blkno = fsbtodb(fs, nb);
            vfs_bio_clrbuf(nbp);
            if (DOINGSOFTDEP(vp)) {
                  softdep_setup_allocindir_meta(nbp, ip, bp,
                      indirs[i - 1].in_off, nb);
                  bdwrite(nbp);
            } else {
                  /*
                   * Write synchronously so that indirect blocks
                   * never point at garbage.
                   */
                  if ((error = bwrite(nbp)) != 0) {
                        brelse(bp);
                        goto fail;
                  }
            }
            bap[indirs[i - 1].in_off] = nb;
            if (allocib == NULL && unwindidx < 0)
                  unwindidx = i - 1;
            /*
             * If required, write synchronously, otherwise use
             * delayed write.
             */
            if (flags & IO_SYNC) {
                  bwrite(bp);
            } else {
                  if (bp->b_bufsize == fs->fs_bsize)
                        bp->b_flags |= B_CLUSTEROK;
                  bdwrite(bp);
            }
      }
      /*
       * If asked only for the indirect block, then return it.
       */
      if (flags & BA_METAONLY) {
            *bpp = bp;
            return (0);
      }
      /*
       * Get the data block, allocating if necessary.
       */
      if (nb == 0) {
            UFS_LOCK(ump);
            pref = ffs_blkpref_ufs1(ip, lbn, indirs[i].in_off, &bap[0]);
            error = ffs_alloc(ip,
                lbn, pref, (int)fs->fs_bsize, cred, &newb);
            if (error) {
                  brelse(bp);
                  goto fail;
            }
            nb = newb;
            *allocblk++ = nb;
            *lbns_remfree++ = lbn;
            nbp = getblk(vp, lbn, fs->fs_bsize, 0, 0, 0);
            nbp->b_blkno = fsbtodb(fs, nb);
            if (flags & BA_CLRBUF)
                  vfs_bio_clrbuf(nbp);
            if (DOINGSOFTDEP(vp))
                  softdep_setup_allocindir_page(ip, lbn, bp,
                      indirs[i].in_off, nb, 0, nbp);
            bap[indirs[i].in_off] = nb;
            /*
             * If required, write synchronously, otherwise use
             * delayed write.
             */
            if (flags & IO_SYNC) {
                  bwrite(bp);
            } else {
                  if (bp->b_bufsize == fs->fs_bsize)
                        bp->b_flags |= B_CLUSTEROK;
                  bdwrite(bp);
            }
            *bpp = nbp;
            return (0);
      }
      brelse(bp);
      if (flags & BA_CLRBUF) {
            int seqcount = (flags & BA_SEQMASK) >> BA_SEQSHIFT;
            if (seqcount && (vp->v_mount->mnt_flag & MNT_NOCLUSTERR) == 0) {
                  error = cluster_read(vp, ip->i_size, lbn,
                      (int)fs->fs_bsize, NOCRED,
                      MAXBSIZE, seqcount, &nbp);
            } else {
                  error = bread(vp, lbn, (int)fs->fs_bsize, NOCRED, &nbp);
            }
            if (error) {
                  brelse(nbp);
                  goto fail;
            }
      } else {
            nbp = getblk(vp, lbn, fs->fs_bsize, 0, 0, 0);
            nbp->b_blkno = fsbtodb(fs, nb);
      }
      *bpp = nbp;
      return (0);
fail:
      /*
       * If we have failed to allocate any blocks, simply return the error.
       * This is the usual case and avoids the need to fsync the file.
       */
      if (allocblk == allociblk && allocib == NULL && unwindidx == -1)
            return (error);
      /*
       * If we have failed part way through block allocation, we
       * have to deallocate any indirect blocks that we have allocated.
       * We have to fsync the file before we start to get rid of all
       * of its dependencies so that we do not leave them dangling.
       * We have to sync it at the end so that the soft updates code
       * does not find any untracked changes. Although this is really
       * slow, running out of disk space is not expected to be a common
       * occurence. The error return from fsync is ignored as we already
       * have an error to return to the user.
       */
      (void) ffs_syncvnode(vp, MNT_WAIT);
      for (deallocated = 0, blkp = allociblk, lbns_remfree = lbns;
           blkp < allocblk; blkp++, lbns_remfree++) {
            /*
             * We shall not leave the freed blocks on the vnode
             * buffer object lists.
             */
            bp = getblk(vp, *lbns_remfree, fs->fs_bsize, 0, 0, GB_NOCREAT);
            if (bp != NULL) {
                  bp->b_flags |= (B_INVAL | B_RELBUF);
                  bp->b_flags &= ~B_ASYNC;
                  brelse(bp);
            }
            deallocated += fs->fs_bsize;
      }
      if (allocib != NULL) {
            *allocib = 0;
      } else if (unwindidx >= 0) {
            int r;

            r = bread(vp, indirs[unwindidx].in_lbn, 
                (int)fs->fs_bsize, NOCRED, &bp);
            if (r) {
                  panic("Could not unwind indirect block, error %d", r);
                  brelse(bp);
            } else {
                  bap = (ufs1_daddr_t *)bp->b_data;
                  bap[indirs[unwindidx].in_off] = 0;
                  if (flags & IO_SYNC) {
                        bwrite(bp);
                  } else {
                        if (bp->b_bufsize == fs->fs_bsize)
                              bp->b_flags |= B_CLUSTEROK;
                        bdwrite(bp);
                  }
            }
      }
      if (deallocated) {
#ifdef QUOTA
            /*
             * Restore user's disk quota because allocation failed.
             */
            (void) chkdq(ip, -btodb(deallocated), cred, FORCE);
#endif
            dp->di_blocks -= btodb(deallocated);
            ip->i_flag |= IN_CHANGE | IN_UPDATE;
      }
      (void) ffs_syncvnode(vp, MNT_WAIT);
      /*
       * After the buffers are invalidated and on-disk pointers are
       * cleared, free the blocks.
       */
      for (blkp = allociblk; blkp < allocblk; blkp++) {
            ffs_blkfree(ump, fs, ip->i_devvp, *blkp, fs->fs_bsize,
                ip->i_number);
      }
      return (error);
}

/*
 * Balloc defines the structure of file system storage
 * by allocating the physical blocks on a device given
 * the inode and the logical block number in a file.
 * This is the allocation strategy for UFS2. Above is
 * the allocation strategy for UFS1.
 */
int
ffs_balloc_ufs2(struct vnode *vp, off_t startoffset, int size,
    struct ucred *cred, int flags, struct buf **bpp)
{
      struct inode *ip;
      struct ufs2_dinode *dp;
      ufs_lbn_t lbn, lastlbn;
      struct fs *fs;
      struct buf *bp, *nbp;
      struct ufsmount *ump;
      struct indir indirs[NIADDR + 2];
      ufs2_daddr_t nb, newb, *bap, pref;
      ufs2_daddr_t *allocib, *blkp, *allocblk, allociblk[NIADDR + 1];
      ufs2_daddr_t *lbns_remfree, lbns[NIADDR + 1];
      int deallocated, osize, nsize, num, i, error;
      int unwindidx = -1;

      ip = VTOI(vp);
      dp = ip->i_din2;
      fs = ip->i_fs;
      ump = ip->i_ump;
      lbn = lblkno(fs, startoffset);
      size = blkoff(fs, startoffset) + size;
      if (size > fs->fs_bsize)
            panic("ffs_balloc_ufs2: blk too big");
      *bpp = NULL;
      if (lbn < 0)
            return (EFBIG);

      /*
       * Check for allocating external data.
       */
      if (flags & IO_EXT) {
            if (lbn >= NXADDR)
                  return (EFBIG);
            /*
             * If the next write will extend the data into a new block,
             * and the data is currently composed of a fragment
             * this fragment has to be extended to be a full block.
             */
            lastlbn = lblkno(fs, dp->di_extsize);
            if (lastlbn < lbn) {
                  nb = lastlbn;
                  osize = sblksize(fs, dp->di_extsize, nb);
                  if (osize < fs->fs_bsize && osize > 0) {
                        UFS_LOCK(ump);
                        error = ffs_realloccg(ip, -1 - nb,
                            dp->di_extb[nb],
                            ffs_blkpref_ufs2(ip, lastlbn, (int)nb,
                            &dp->di_extb[0]), osize,
                            (int)fs->fs_bsize, cred, &bp);
                        if (error)
                              return (error);
                        if (DOINGSOFTDEP(vp))
                              softdep_setup_allocext(ip, nb,
                                  dbtofsb(fs, bp->b_blkno),
                                  dp->di_extb[nb],
                                  fs->fs_bsize, osize, bp);
                        dp->di_extsize = smalllblktosize(fs, nb + 1);
                        dp->di_extb[nb] = dbtofsb(fs, bp->b_blkno);
                        bp->b_xflags |= BX_ALTDATA;
                        ip->i_flag |= IN_CHANGE | IN_UPDATE;
                        if (flags & IO_SYNC)
                              bwrite(bp);
                        else
                              bawrite(bp);
                  }
            }
            /*
             * All blocks are direct blocks
             */
            if (flags & BA_METAONLY)
                  panic("ffs_balloc_ufs2: BA_METAONLY for ext block");
            nb = dp->di_extb[lbn];
            if (nb != 0 && dp->di_extsize >= smalllblktosize(fs, lbn + 1)) {
                  error = bread(vp, -1 - lbn, fs->fs_bsize, NOCRED, &bp);
                  if (error) {
                        brelse(bp);
                        return (error);
                  }
                  bp->b_blkno = fsbtodb(fs, nb);
                  bp->b_xflags |= BX_ALTDATA;
                  *bpp = bp;
                  return (0);
            }
            if (nb != 0) {
                  /*
                   * Consider need to reallocate a fragment.
                   */
                  osize = fragroundup(fs, blkoff(fs, dp->di_extsize));
                  nsize = fragroundup(fs, size);
                  if (nsize <= osize) {
                        error = bread(vp, -1 - lbn, osize, NOCRED, &bp);
                        if (error) {
                              brelse(bp);
                              return (error);
                        }
                        bp->b_blkno = fsbtodb(fs, nb);
                        bp->b_xflags |= BX_ALTDATA;
                  } else {
                        UFS_LOCK(ump);
                        error = ffs_realloccg(ip, -1 - lbn,
                            dp->di_extb[lbn],
                            ffs_blkpref_ufs2(ip, lbn, (int)lbn,
                            &dp->di_extb[0]), osize, nsize, cred, &bp);
                        if (error)
                              return (error);
                        bp->b_xflags |= BX_ALTDATA;
                        if (DOINGSOFTDEP(vp))
                              softdep_setup_allocext(ip, lbn,
                                  dbtofsb(fs, bp->b_blkno), nb,
                                  nsize, osize, bp);
                  }
            } else {
                  if (dp->di_extsize < smalllblktosize(fs, lbn + 1))
                        nsize = fragroundup(fs, size);
                  else
                        nsize = fs->fs_bsize;
                  UFS_LOCK(ump);
                  error = ffs_alloc(ip, lbn,
                     ffs_blkpref_ufs2(ip, lbn, (int)lbn, &dp->di_extb[0]),
                     nsize, cred, &newb);
                  if (error)
                        return (error);
                  bp = getblk(vp, -1 - lbn, nsize, 0, 0, 0);
                  bp->b_blkno = fsbtodb(fs, newb);
                  bp->b_xflags |= BX_ALTDATA;
                  if (flags & BA_CLRBUF)
                        vfs_bio_clrbuf(bp);
                  if (DOINGSOFTDEP(vp))
                        softdep_setup_allocext(ip, lbn, newb, 0,
                            nsize, 0, bp);
            }
            dp->di_extb[lbn] = dbtofsb(fs, bp->b_blkno);
            ip->i_flag |= IN_CHANGE | IN_UPDATE;
            *bpp = bp;
            return (0);
      }
      /*
       * If the next write will extend the file into a new block,
       * and the file is currently composed of a fragment
       * this fragment has to be extended to be a full block.
       */
      lastlbn = lblkno(fs, ip->i_size);
      if (lastlbn < NDADDR && lastlbn < lbn) {
            nb = lastlbn;
            osize = blksize(fs, ip, nb);
            if (osize < fs->fs_bsize && osize > 0) {
                  UFS_LOCK(ump);
                  error = ffs_realloccg(ip, nb, dp->di_db[nb],
                        ffs_blkpref_ufs2(ip, lastlbn, (int)nb,
                            &dp->di_db[0]), osize, (int)fs->fs_bsize,
                            cred, &bp);
                  if (error)
                        return (error);
                  if (DOINGSOFTDEP(vp))
                        softdep_setup_allocdirect(ip, nb,
                            dbtofsb(fs, bp->b_blkno),
                            dp->di_db[nb],
                            fs->fs_bsize, osize, bp);
                  ip->i_size = smalllblktosize(fs, nb + 1);
                  dp->di_size = ip->i_size;
                  dp->di_db[nb] = dbtofsb(fs, bp->b_blkno);
                  ip->i_flag |= IN_CHANGE | IN_UPDATE;
                  if (flags & IO_SYNC)
                        bwrite(bp);
                  else
                        bawrite(bp);
            }
      }
      /*
       * The first NDADDR blocks are direct blocks
       */
      if (lbn < NDADDR) {
            if (flags & BA_METAONLY)
                  panic("ffs_balloc_ufs2: BA_METAONLY for direct block");
            nb = dp->di_db[lbn];
            if (nb != 0 && ip->i_size >= smalllblktosize(fs, lbn + 1)) {
                  error = bread(vp, lbn, fs->fs_bsize, NOCRED, &bp);
                  if (error) {
                        brelse(bp);
                        return (error);
                  }
                  bp->b_blkno = fsbtodb(fs, nb);
                  *bpp = bp;
                  return (0);
            }
            if (nb != 0) {
                  /*
                   * Consider need to reallocate a fragment.
                   */
                  osize = fragroundup(fs, blkoff(fs, ip->i_size));
                  nsize = fragroundup(fs, size);
                  if (nsize <= osize) {
                        error = bread(vp, lbn, osize, NOCRED, &bp);
                        if (error) {
                              brelse(bp);
                              return (error);
                        }
                        bp->b_blkno = fsbtodb(fs, nb);
                  } else {
                        UFS_LOCK(ump);
                        error = ffs_realloccg(ip, lbn, dp->di_db[lbn],
                            ffs_blkpref_ufs2(ip, lbn, (int)lbn,
                               &dp->di_db[0]), osize, nsize, cred, &bp);
                        if (error)
                              return (error);
                        if (DOINGSOFTDEP(vp))
                              softdep_setup_allocdirect(ip, lbn,
                                  dbtofsb(fs, bp->b_blkno), nb,
                                  nsize, osize, bp);
                  }
            } else {
                  if (ip->i_size < smalllblktosize(fs, lbn + 1))
                        nsize = fragroundup(fs, size);
                  else
                        nsize = fs->fs_bsize;
                  UFS_LOCK(ump);
                  error = ffs_alloc(ip, lbn,
                      ffs_blkpref_ufs2(ip, lbn, (int)lbn,
                        &dp->di_db[0]), nsize, cred, &newb);
                  if (error)
                        return (error);
                  bp = getblk(vp, lbn, nsize, 0, 0, 0);
                  bp->b_blkno = fsbtodb(fs, newb);
                  if (flags & BA_CLRBUF)
                        vfs_bio_clrbuf(bp);
                  if (DOINGSOFTDEP(vp))
                        softdep_setup_allocdirect(ip, lbn, newb, 0,
                            nsize, 0, bp);
            }
            dp->di_db[lbn] = dbtofsb(fs, bp->b_blkno);
            ip->i_flag |= IN_CHANGE | IN_UPDATE;
            *bpp = bp;
            return (0);
      }
      /*
       * Determine the number of levels of indirection.
       */
      pref = 0;
      if ((error = ufs_getlbns(vp, lbn, indirs, &num)) != 0)
            return(error);
#ifdef DIAGNOSTIC
      if (num < 1)
            panic ("ffs_balloc_ufs2: ufs_getlbns returned indirect block");
#endif
      /*
       * Fetch the first indirect block allocating if necessary.
       */
      --num;
      nb = dp->di_ib[indirs[0].in_off];
      allocib = NULL;
      allocblk = allociblk;
      lbns_remfree = lbns;
      if (nb == 0) {
            UFS_LOCK(ump);
            pref = ffs_blkpref_ufs2(ip, lbn, 0, (ufs2_daddr_t *)0);
              if ((error = ffs_alloc(ip, lbn, pref, (int)fs->fs_bsize,
                cred, &newb)) != 0)
                  return (error);
            nb = newb;
            *allocblk++ = nb;
            *lbns_remfree++ = indirs[1].in_lbn;
            bp = getblk(vp, indirs[1].in_lbn, fs->fs_bsize, 0, 0, 0);
            bp->b_blkno = fsbtodb(fs, nb);
            vfs_bio_clrbuf(bp);
            if (DOINGSOFTDEP(vp)) {
                  softdep_setup_allocdirect(ip, NDADDR + indirs[0].in_off,
                      newb, 0, fs->fs_bsize, 0, bp);
                  bdwrite(bp);
            } else {
                  /*
                   * Write synchronously so that indirect blocks
                   * never point at garbage.
                   */
                  if (DOINGASYNC(vp))
                        bdwrite(bp);
                  else if ((error = bwrite(bp)) != 0)
                        goto fail;
            }
            allocib = &dp->di_ib[indirs[0].in_off];
            *allocib = nb;
            ip->i_flag |= IN_CHANGE | IN_UPDATE;
      }
      /*
       * Fetch through the indirect blocks, allocating as necessary.
       */
      for (i = 1;;) {
            error = bread(vp,
                indirs[i].in_lbn, (int)fs->fs_bsize, NOCRED, &bp);
            if (error) {
                  brelse(bp);
                  goto fail;
            }
            bap = (ufs2_daddr_t *)bp->b_data;
            nb = bap[indirs[i].in_off];
            if (i == num)
                  break;
            i += 1;
            if (nb != 0) {
                  bqrelse(bp);
                  continue;
            }
            UFS_LOCK(ump);
            if (pref == 0)
                  pref = ffs_blkpref_ufs2(ip, lbn, 0, (ufs2_daddr_t *)0);
            if ((error =
                ffs_alloc(ip, lbn, pref, (int)fs->fs_bsize, cred, &newb)) != 0) {
                  brelse(bp);
                  goto fail;
            }
            nb = newb;
            *allocblk++ = nb;
            *lbns_remfree++ = indirs[i].in_lbn;
            nbp = getblk(vp, indirs[i].in_lbn, fs->fs_bsize, 0, 0, 0);
            nbp->b_blkno = fsbtodb(fs, nb);
            vfs_bio_clrbuf(nbp);
            if (DOINGSOFTDEP(vp)) {
                  softdep_setup_allocindir_meta(nbp, ip, bp,
                      indirs[i - 1].in_off, nb);
                  bdwrite(nbp);
            } else {
                  /*
                   * Write synchronously so that indirect blocks
                   * never point at garbage.
                   */
                  if ((error = bwrite(nbp)) != 0) {
                        brelse(bp);
                        goto fail;
                  }
            }
            bap[indirs[i - 1].in_off] = nb;
            if (allocib == NULL && unwindidx < 0)
                  unwindidx = i - 1;
            /*
             * If required, write synchronously, otherwise use
             * delayed write.
             */
            if (flags & IO_SYNC) {
                  bwrite(bp);
            } else {
                  if (bp->b_bufsize == fs->fs_bsize)
                        bp->b_flags |= B_CLUSTEROK;
                  bdwrite(bp);
            }
      }
      /*
       * If asked only for the indirect block, then return it.
       */
      if (flags & BA_METAONLY) {
            *bpp = bp;
            return (0);
      }
      /*
       * Get the data block, allocating if necessary.
       */
      if (nb == 0) {
            UFS_LOCK(ump);
            pref = ffs_blkpref_ufs2(ip, lbn, indirs[i].in_off, &bap[0]);
            error = ffs_alloc(ip,
                lbn, pref, (int)fs->fs_bsize, cred, &newb);
            if (error) {
                  brelse(bp);
                  goto fail;
            }
            nb = newb;
            *allocblk++ = nb;
            *lbns_remfree++ = lbn;
            nbp = getblk(vp, lbn, fs->fs_bsize, 0, 0, 0);
            nbp->b_blkno = fsbtodb(fs, nb);
            if (flags & BA_CLRBUF)
                  vfs_bio_clrbuf(nbp);
            if (DOINGSOFTDEP(vp))
                  softdep_setup_allocindir_page(ip, lbn, bp,
                      indirs[i].in_off, nb, 0, nbp);
            bap[indirs[i].in_off] = nb;
            /*
             * If required, write synchronously, otherwise use
             * delayed write.
             */
            if (flags & IO_SYNC) {
                  bwrite(bp);
            } else {
                  if (bp->b_bufsize == fs->fs_bsize)
                        bp->b_flags |= B_CLUSTEROK;
                  bdwrite(bp);
            }
            *bpp = nbp;
            return (0);
      }
      brelse(bp);
      /*
       * If requested clear invalid portions of the buffer.  If we
       * have to do a read-before-write (typical if BA_CLRBUF is set),
       * try to do some read-ahead in the sequential case to reduce
       * the number of I/O transactions.
       */
      if (flags & BA_CLRBUF) {
            int seqcount = (flags & BA_SEQMASK) >> BA_SEQSHIFT;
            if (seqcount && (vp->v_mount->mnt_flag & MNT_NOCLUSTERR) == 0) {
                  error = cluster_read(vp, ip->i_size, lbn,
                      (int)fs->fs_bsize, NOCRED,
                      MAXBSIZE, seqcount, &nbp);
            } else {
                  error = bread(vp, lbn, (int)fs->fs_bsize, NOCRED, &nbp);
            }
            if (error) {
                  brelse(nbp);
                  goto fail;
            }
      } else {
            nbp = getblk(vp, lbn, fs->fs_bsize, 0, 0, 0);
            nbp->b_blkno = fsbtodb(fs, nb);
      }
      *bpp = nbp;
      return (0);
fail:
      /*
       * If we have failed to allocate any blocks, simply return the error.
       * This is the usual case and avoids the need to fsync the file.
       */
      if (allocblk == allociblk && allocib == NULL && unwindidx == -1)
            return (error);
      /*
       * If we have failed part way through block allocation, we
       * have to deallocate any indirect blocks that we have allocated.
       * We have to fsync the file before we start to get rid of all
       * of its dependencies so that we do not leave them dangling.
       * We have to sync it at the end so that the soft updates code
       * does not find any untracked changes. Although this is really
       * slow, running out of disk space is not expected to be a common
       * occurence. The error return from fsync is ignored as we already
       * have an error to return to the user.
       */
      (void) ffs_syncvnode(vp, MNT_WAIT);
      for (deallocated = 0, blkp = allociblk, lbns_remfree = lbns;
           blkp < allocblk; blkp++, lbns_remfree++) {
            /*
             * We shall not leave the freed blocks on the vnode
             * buffer object lists.
             */
            bp = getblk(vp, *lbns_remfree, fs->fs_bsize, 0, 0, GB_NOCREAT);
            if (bp != NULL) {
                  bp->b_flags |= (B_INVAL | B_RELBUF);
                  bp->b_flags &= ~B_ASYNC;
                  brelse(bp);
            }
            deallocated += fs->fs_bsize;
      }
      if (allocib != NULL) {
            *allocib = 0;
      } else if (unwindidx >= 0) {
            int r;

            r = bread(vp, indirs[unwindidx].in_lbn, 
                (int)fs->fs_bsize, NOCRED, &bp);
            if (r) {
                  panic("Could not unwind indirect block, error %d", r);
                  brelse(bp);
            } else {
                  bap = (ufs2_daddr_t *)bp->b_data;
                  bap[indirs[unwindidx].in_off] = 0;
                  if (flags & IO_SYNC) {
                        bwrite(bp);
                  } else {
                        if (bp->b_bufsize == fs->fs_bsize)
                              bp->b_flags |= B_CLUSTEROK;
                        bdwrite(bp);
                  }
            }
      }
      if (deallocated) {
#ifdef QUOTA
            /*
             * Restore user's disk quota because allocation failed.
             */
            (void) chkdq(ip, -btodb(deallocated), cred, FORCE);
#endif
            dp->di_blocks -= btodb(deallocated);
            ip->i_flag |= IN_CHANGE | IN_UPDATE;
      }
      (void) ffs_syncvnode(vp, MNT_WAIT);
      /*
       * After the buffers are invalidated and on-disk pointers are
       * cleared, free the blocks.
       */
      for (blkp = allociblk; blkp < allocblk; blkp++) {
            ffs_blkfree(ump, fs, ip->i_devvp, *blkp, fs->fs_bsize,
                ip->i_number);
      }
      return (error);
}

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