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 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *   Copyright (C) International Business Machines Corp., 2000-2004
  *   Portions Copyright (C) Tino Reichardt, 2012
  */
 
 #include <linux/fs.h>
 #include <linux/slab.h>
 #include "jfs_incore.h"
 #include "jfs_superblock.h"
 #include "jfs_dmap.h"
 #include "jfs_imap.h"
 #include "jfs_lock.h"
 #include "jfs_metapage.h"
 #include "jfs_debug.h"
 #include "jfs_discard.h"
 
 /*
  *  SERIALIZATION of the Block Allocation Map.
  *
  *  the working state of the block allocation map is accessed in
  *  two directions:
  *
  *  1) allocation and free requests that start at the dmap
  *     level and move up through the dmap control pages (i.e.
  *     the vast majority of requests).
  *
  *  2) allocation requests that start at dmap control page
  *     level and work down towards the dmaps.
  *
  *  the serialization scheme used here is as follows.
  *
  *  requests which start at the bottom are serialized against each
  *  other through buffers and each requests holds onto its buffers
  *  as it works it way up from a single dmap to the required level
  *  of dmap control page.
  *  requests that start at the top are serialized against each other
  *  and request that start from the bottom by the multiple read/single
  *  write inode lock of the bmap inode. requests starting at the top
  *  take this lock in write mode while request starting at the bottom
  *  take the lock in read mode.  a single top-down request may proceed
  *  exclusively while multiple bottoms-up requests may proceed
  *  simultaneously (under the protection of busy buffers).
  *
  *  in addition to information found in dmaps and dmap control pages,
  *  the working state of the block allocation map also includes read/
  *  write information maintained in the bmap descriptor (i.e. total
  *  free block count, allocation group level free block counts).
  *  a single exclusive lock (BMAP_LOCK) is used to guard this information
  *  in the face of multiple-bottoms up requests.
  *  (lock ordering: IREAD_LOCK, BMAP_LOCK);
  *
  *  accesses to the persistent state of the block allocation map (limited
  *  to the persistent bitmaps in dmaps) is guarded by (busy) buffers.
  */
 
 #define BMAP_LOCK_INIT(bmp) mutex_init(&bmp->db_bmaplock)
 #define BMAP_LOCK(bmp)      mutex_lock(&bmp->db_bmaplock)
 #define BMAP_UNLOCK(bmp)    mutex_unlock(&bmp->db_bmaplock)
 
 /*
  * forward references
  */
 static void dbAllocBits(struct bmap * bmp, struct dmap * dp, s64 blkno,
             int nblocks);
 static void dbSplit(dmtree_t * tp, int leafno, int splitsz, int newval);
 static int dbBackSplit(dmtree_t * tp, int leafno);
 static int dbJoin(dmtree_t * tp, int leafno, int newval);
 static void dbAdjTree(dmtree_t * tp, int leafno, int newval);
 static int dbAdjCtl(struct bmap * bmp, s64 blkno, int newval, int alloc,
             int level);
 static int dbAllocAny(struct bmap * bmp, s64 nblocks, int l2nb, s64 * results);
 static int dbAllocNext(struct bmap * bmp, struct dmap * dp, s64 blkno,
                int nblocks);
 static int dbAllocNear(struct bmap * bmp, struct dmap * dp, s64 blkno,
                int nblocks,
                int l2nb, s64 * results);
 static int dbAllocDmap(struct bmap * bmp, struct dmap * dp, s64 blkno,
                int nblocks);
 static int dbAllocDmapLev(struct bmap * bmp, struct dmap * dp, int nblocks,
               int l2nb,
               s64 * results);
 static int dbAllocAG(struct bmap * bmp, int agno, s64 nblocks, int l2nb,
              s64 * results);
 static int dbAllocCtl(struct bmap * bmp, s64 nblocks, int l2nb, s64 blkno,
               s64 * results);
 static int dbExtend(struct inode *ip, s64 blkno, s64 nblocks, s64 addnblocks);
 static int dbFindBits(u32 word, int l2nb);
 static int dbFindCtl(struct bmap * bmp, int l2nb, int level, s64 * blkno);
 static int dbFindLeaf(dmtree_t * tp, int l2nb, int *leafidx);
 static int dbFreeBits(struct bmap * bmp, struct dmap * dp, s64 blkno,
               int nblocks);
 static int dbFreeDmap(struct bmap * bmp, struct dmap * dp, s64 blkno,
               int nblocks);
 static int dbMaxBud(u8 * cp);
 static int blkstol2(s64 nb);
 
 static int cntlz(u32 value);
 static int cnttz(u32 word);
 
 static int dbAllocDmapBU(struct bmap * bmp, struct dmap * dp, s64 blkno,
              int nblocks);
 static int dbInitDmap(struct dmap * dp, s64 blkno, int nblocks);
 static int dbInitDmapTree(struct dmap * dp);
 static int dbInitTree(struct dmaptree * dtp);
 static int dbInitDmapCtl(struct dmapctl * dcp, int level, int i);
 static int dbGetL2AGSize(s64 nblocks);
 
 /*
  *  buddy table
  *
  * table used for determining buddy sizes within characters of
  * dmap bitmap words.  the characters themselves serve as indexes
  * into the table, with the table elements yielding the maximum
  * binary buddy of free bits within the character.
  */
 static const s8 budtab[256] = {
     3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
     2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
     2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
     2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
     2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
     2, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0,
     2, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0,
     2, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0,
     2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
     2, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0,
     2, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0,
     2, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0,
     2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
     2, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0,
     2, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0,
     2, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, -1
 };
 
 /*
  * NAME:    dbMount()
  *
  * FUNCTION:    initializate the block allocation map.
  *
  *      memory is allocated for the in-core bmap descriptor and
  *      the in-core descriptor is initialized from disk.
  *
  * PARAMETERS:
  *  ipbmap  - pointer to in-core inode for the block map.
  *
  * RETURN VALUES:
  *  0   - success
  *  -ENOMEM - insufficient memory
  *  -EIO    - i/o error
  *  -EINVAL - wrong bmap data
  */
 int dbMount(struct inode *ipbmap)
 {
     struct bmap *bmp;
     struct dbmap_disk *dbmp_le;
     struct metapage *mp;
     int i;
 
     /*
      * allocate/initialize the in-memory bmap descriptor
      */
     /* allocate memory for the in-memory bmap descriptor */
     bmp = kmalloc(sizeof(struct bmap), GFP_KERNEL);
     if (bmp == NULL)
         return -ENOMEM;
 
     /* read the on-disk bmap descriptor. */
     mp = read_metapage(ipbmap,
                BMAPBLKNO << JFS_SBI(ipbmap->i_sb)->l2nbperpage,
                PSIZE, 0);
     if (mp == NULL) {
         kfree(bmp);
         return -EIO;
     }
 
     /* copy the on-disk bmap descriptor to its in-memory version. */
     dbmp_le = (struct dbmap_disk *) mp->data;
     bmp->db_mapsize = le64_to_cpu(dbmp_le->dn_mapsize);
     bmp->db_nfree = le64_to_cpu(dbmp_le->dn_nfree);
     bmp->db_l2nbperpage = le32_to_cpu(dbmp_le->dn_l2nbperpage);
     bmp->db_numag = le32_to_cpu(dbmp_le->dn_numag);
     if (!bmp->db_numag) {
         release_metapage(mp);
         kfree(bmp);
         return -EINVAL;
     }
 
     bmp->db_maxlevel = le32_to_cpu(dbmp_le->dn_maxlevel);
     bmp->db_maxag = le32_to_cpu(dbmp_le->dn_maxag);
     bmp->db_agpref = le32_to_cpu(dbmp_le->dn_agpref);
     bmp->db_aglevel = le32_to_cpu(dbmp_le->dn_aglevel);
     bmp->db_agheight = le32_to_cpu(dbmp_le->dn_agheight);
     bmp->db_agwidth = le32_to_cpu(dbmp_le->dn_agwidth);
     bmp->db_agstart = le32_to_cpu(dbmp_le->dn_agstart);
     bmp->db_agl2size = le32_to_cpu(dbmp_le->dn_agl2size);
     for (i = 0; i < MAXAG; i++)
         bmp->db_agfree[i] = le64_to_cpu(dbmp_le->dn_agfree[i]);
     bmp->db_agsize = le64_to_cpu(dbmp_le->dn_agsize);
     bmp->db_maxfreebud = dbmp_le->dn_maxfreebud;
 
     /* release the buffer. */
     release_metapage(mp);
 
     /* bind the bmap inode and the bmap descriptor to each other. */
     bmp->db_ipbmap = ipbmap;
     JFS_SBI(ipbmap->i_sb)->bmap = bmp;
 
     memset(bmp->db_active, 0, sizeof(bmp->db_active));
 
     /*
      * allocate/initialize the bmap lock
      */
     BMAP_LOCK_INIT(bmp);
 
     return (0);
 }
 
 
 /*
  * NAME:    dbUnmount()
  *
  * FUNCTION:    terminate the block allocation map in preparation for
  *      file system unmount.
  *
  *      the in-core bmap descriptor is written to disk and
  *      the memory for this descriptor is freed.
  *
  * PARAMETERS:
  *  ipbmap  - pointer to in-core inode for the block map.
  *
  * RETURN VALUES:
  *  0   - success
  *  -EIO    - i/o error
  */
 int dbUnmount(struct inode *ipbmap, int mounterror)
 {
     struct bmap *bmp = JFS_SBI(ipbmap->i_sb)->bmap;
 
     if (!(mounterror || isReadOnly(ipbmap)))
         dbSync(ipbmap);
 
     /*
      * Invalidate the page cache buffers
      */
     truncate_inode_pages(ipbmap->i_mapping, 0);
 
     /* free the memory for the in-memory bmap. */
     kfree(bmp);
 
     return (0);
 }
 
 /*
  *  dbSync()
  */
 int dbSync(struct inode *ipbmap)
 {
     struct dbmap_disk *dbmp_le;
     struct bmap *bmp = JFS_SBI(ipbmap->i_sb)->bmap;
     struct metapage *mp;
     int i;
 
     /*
      * write bmap global control page
      */
     /* get the buffer for the on-disk bmap descriptor. */
     mp = read_metapage(ipbmap,
                BMAPBLKNO << JFS_SBI(ipbmap->i_sb)->l2nbperpage,
                PSIZE, 0);
     if (mp == NULL) {
         jfs_err("dbSync: read_metapage failed!");
         return -EIO;
     }
     /* copy the in-memory version of the bmap to the on-disk version */
     dbmp_le = (struct dbmap_disk *) mp->data;
     dbmp_le->dn_mapsize = cpu_to_le64(bmp->db_mapsize);
     dbmp_le->dn_nfree = cpu_to_le64(bmp->db_nfree);
     dbmp_le->dn_l2nbperpage = cpu_to_le32(bmp->db_l2nbperpage);
     dbmp_le->dn_numag = cpu_to_le32(bmp->db_numag);
     dbmp_le->dn_maxlevel = cpu_to_le32(bmp->db_maxlevel);
     dbmp_le->dn_maxag = cpu_to_le32(bmp->db_maxag);
     dbmp_le->dn_agpref = cpu_to_le32(bmp->db_agpref);
     dbmp_le->dn_aglevel = cpu_to_le32(bmp->db_aglevel);
     dbmp_le->dn_agheight = cpu_to_le32(bmp->db_agheight);
     dbmp_le->dn_agwidth = cpu_to_le32(bmp->db_agwidth);
     dbmp_le->dn_agstart = cpu_to_le32(bmp->db_agstart);
     dbmp_le->dn_agl2size = cpu_to_le32(bmp->db_agl2size);
     for (i = 0; i < MAXAG; i++)
         dbmp_le->dn_agfree[i] = cpu_to_le64(bmp->db_agfree[i]);
     dbmp_le->dn_agsize = cpu_to_le64(bmp->db_agsize);
     dbmp_le->dn_maxfreebud = bmp->db_maxfreebud;
 
     /* write the buffer */
     write_metapage(mp);
 
     /*
      * write out dirty pages of bmap
      */
     filemap_write_and_wait(ipbmap->i_mapping);
 
     diWriteSpecial(ipbmap, 0);
 
     return (0);
 }
 
 /*
  * NAME:    dbFree()
  *
  * FUNCTION:    free the specified block range from the working block
  *      allocation map.
  *
  *      the blocks will be free from the working map one dmap
  *      at a time.
  *
  * PARAMETERS:
  *  ip  - pointer to in-core inode;
  *  blkno   - starting block number to be freed.
  *  nblocks - number of blocks to be freed.
  *
  * RETURN VALUES:
  *  0   - success
  *  -EIO    - i/o error
  */
 int dbFree(struct inode *ip, s64 blkno, s64 nblocks)
 {
     struct metapage *mp;
     struct dmap *dp;
     int nb, rc;
     s64 lblkno, rem;
     struct inode *ipbmap = JFS_SBI(ip->i_sb)->ipbmap;
     struct bmap *bmp = JFS_SBI(ip->i_sb)->bmap;
     struct super_block *sb = ipbmap->i_sb;
 
     IREAD_LOCK(ipbmap, RDWRLOCK_DMAP);
 
     /* block to be freed better be within the mapsize. */
     if (unlikely((blkno == 0) || (blkno + nblocks > bmp->db_mapsize))) {
         IREAD_UNLOCK(ipbmap);
         printk(KERN_ERR "blkno = %Lx, nblocks = %Lx\n",
                (unsigned long long) blkno,
                (unsigned long long) nblocks);
         jfs_error(ip->i_sb, "block to be freed is outside the map\n");
         return -EIO;
     }
 
     /**
      * TRIM the blocks, when mounted with discard option
      */
     if (JFS_SBI(sb)->flag & JFS_DISCARD)
         if (JFS_SBI(sb)->minblks_trim <= nblocks)
             jfs_issue_discard(ipbmap, blkno, nblocks);
 
     /*
      * free the blocks a dmap at a time.
      */
     mp = NULL;
     for (rem = nblocks; rem > 0; rem -= nb, blkno += nb) {
         /* release previous dmap if any */
         if (mp) {
             write_metapage(mp);
         }
 
         /* get the buffer for the current dmap. */
         lblkno = BLKTODMAP(blkno, bmp->db_l2nbperpage);
         mp = read_metapage(ipbmap, lblkno, PSIZE, 0);
         if (mp == NULL) {
             IREAD_UNLOCK(ipbmap);
             return -EIO;
         }
         dp = (struct dmap *) mp->data;
 
         /* determine the number of blocks to be freed from
          * this dmap.
          */
         nb = min(rem, BPERDMAP - (blkno & (BPERDMAP - 1)));
 
         /* free the blocks. */
         if ((rc = dbFreeDmap(bmp, dp, blkno, nb))) {
             jfs_error(ip->i_sb, "error in block map\n");
             release_metapage(mp);
             IREAD_UNLOCK(ipbmap);
             return (rc);
         }
     }
 
     /* write the last buffer. */
     if (mp)
         write_metapage(mp);
 
     IREAD_UNLOCK(ipbmap);
 
     return (0);
 }
 
 
 /*
  * NAME:    dbUpdatePMap()
  *
  * FUNCTION:    update the allocation state (free or allocate) of the
  *      specified block range in the persistent block allocation map.
  *
  *      the blocks will be updated in the persistent map one
  *      dmap at a time.
  *
  * PARAMETERS:
  *  ipbmap  - pointer to in-core inode for the block map.
  *  free    - 'true' if block range is to be freed from the persistent
  *        map; 'false' if it is to be allocated.
  *  blkno   - starting block number of the range.
  *  nblocks - number of contiguous blocks in the range.
  *  tblk    - transaction block;
  *
  * RETURN VALUES:
  *  0   - success
  *  -EIO    - i/o error
  */
 int
 dbUpdatePMap(struct inode *ipbmap,
          int free, s64 blkno, s64 nblocks, struct tblock * tblk)
 {
     int nblks, dbitno, wbitno, rbits;
     int word, nbits, nwords;
     struct bmap *bmp = JFS_SBI(ipbmap->i_sb)->bmap;
     s64 lblkno, rem, lastlblkno;
     u32 mask;
     struct dmap *dp;
     struct metapage *mp;
     struct jfs_log *log;
     int lsn, difft, diffp;
     unsigned long flags;
 
     /* the blocks better be within the mapsize. */
     if (blkno + nblocks > bmp->db_mapsize) {
         printk(KERN_ERR "blkno = %Lx, nblocks = %Lx\n",
                (unsigned long long) blkno,
                (unsigned long long) nblocks);
         jfs_error(ipbmap->i_sb, "blocks are outside the map\n");
         return -EIO;
     }
 
     /* compute delta of transaction lsn from log syncpt */
     lsn = tblk->lsn;
     log = (struct jfs_log *) JFS_SBI(tblk->sb)->log;
     logdiff(difft, lsn, log);
 
     /*
      * update the block state a dmap at a time.
      */
     mp = NULL;
     lastlblkno = 0;
     for (rem = nblocks; rem > 0; rem -= nblks, blkno += nblks) {
         /* get the buffer for the current dmap. */
         lblkno = BLKTODMAP(blkno, bmp->db_l2nbperpage);
         if (lblkno != lastlblkno) {
             if (mp) {
                 write_metapage(mp);
             }
 
             mp = read_metapage(bmp->db_ipbmap, lblkno, PSIZE,
                        0);
             if (mp == NULL)
                 return -EIO;
             metapage_wait_for_io(mp);
         }
         dp = (struct dmap *) mp->data;
 
         /* determine the bit number and word within the dmap of
          * the starting block.  also determine how many blocks
          * are to be updated within this dmap.
          */
         dbitno = blkno & (BPERDMAP - 1);
         word = dbitno >> L2DBWORD;
         nblks = min(rem, (s64)BPERDMAP - dbitno);
 
         /* update the bits of the dmap words. the first and last
          * words may only have a subset of their bits updated. if
          * this is the case, we'll work against that word (i.e.
          * partial first and/or last) only in a single pass.  a
          * single pass will also be used to update all words that
          * are to have all their bits updated.
          */
         for (rbits = nblks; rbits > 0;
              rbits -= nbits, dbitno += nbits) {
             /* determine the bit number within the word and
              * the number of bits within the word.
              */
             wbitno = dbitno & (DBWORD - 1);
             nbits = min(rbits, DBWORD - wbitno);
 
             /* check if only part of the word is to be updated. */
             if (nbits < DBWORD) {
                 /* update (free or allocate) the bits
                  * in this word.
                  */
                 mask =
                     (ONES << (DBWORD - nbits) >> wbitno);
                 if (free)
                     dp->pmap[word] &=
                         cpu_to_le32(~mask);
                 else
                     dp->pmap[word] |=
                         cpu_to_le32(mask);
 
                 word += 1;
             } else {
                 /* one or more words are to have all
                  * their bits updated.  determine how
                  * many words and how many bits.
                  */
                 nwords = rbits >> L2DBWORD;
                 nbits = nwords << L2DBWORD;
 
                 /* update (free or allocate) the bits
                  * in these words.
                  */
                 if (free)
                     memset(&dp->pmap[word], 0,
                            nwords * 4);
                 else
                     memset(&dp->pmap[word], (int) ONES,
                            nwords * 4);
 
                 word += nwords;
             }
         }
 
         /*
          * update dmap lsn
          */
         if (lblkno == lastlblkno)
             continue;
 
         lastlblkno = lblkno;
 
         LOGSYNC_LOCK(log, flags);
         if (mp->lsn != 0) {
             /* inherit older/smaller lsn */
             logdiff(diffp, mp->lsn, log);
             if (difft < diffp) {
                 mp->lsn = lsn;
 
                 /* move bp after tblock in logsync list */
                 list_move(&mp->synclist, &tblk->synclist);
             }
 
             /* inherit younger/larger clsn */
             logdiff(difft, tblk->clsn, log);
             logdiff(diffp, mp->clsn, log);
             if (difft > diffp)
                 mp->clsn = tblk->clsn;
         } else {
             mp->log = log;
             mp->lsn = lsn;
 
             /* insert bp after tblock in logsync list */
             log->count++;
             list_add(&mp->synclist, &tblk->synclist);
 
             mp->clsn = tblk->clsn;
         }
         LOGSYNC_UNLOCK(log, flags);
     }
 
     /* write the last buffer. */
     if (mp) {
         write_metapage(mp);
     }
 
     return (0);
 }
 
 
 /*
  * NAME:    dbNextAG()
  *
  * FUNCTION:    find the preferred allocation group for new allocations.
  *
  *      Within the allocation groups, we maintain a preferred
  *      allocation group which consists of a group with at least
  *      average free space.  It is the preferred group that we target
  *      new inode allocation towards.  The tie-in between inode
  *      allocation and block allocation occurs as we allocate the
  *      first (data) block of an inode and specify the inode (block)
  *      as the allocation hint for this block.
  *
  *      We try to avoid having more than one open file growing in
  *      an allocation group, as this will lead to fragmentation.
  *      This differs from the old OS/2 method of trying to keep
  *      empty ags around for large allocations.
  *
  * PARAMETERS:
  *  ipbmap  - pointer to in-core inode for the block map.
  *
  * RETURN VALUES:
  *  the preferred allocation group number.
  */
 int dbNextAG(struct inode *ipbmap)
 {
     s64 avgfree;
     int agpref;
     s64 hwm = 0;
     int i;
     int next_best = -1;
     struct bmap *bmp = JFS_SBI(ipbmap->i_sb)->bmap;
 
     BMAP_LOCK(bmp);
 
     /* determine the average number of free blocks within the ags. */
     avgfree = (u32)bmp->db_nfree / bmp->db_numag;
 
     /*
      * if the current preferred ag does not have an active allocator
      * and has at least average freespace, return it
      */
     agpref = bmp->db_agpref;
     if ((atomic_read(&bmp->db_active[agpref]) == 0) &&
         (bmp->db_agfree[agpref] >= avgfree))
         goto unlock;
 
     /* From the last preferred ag, find the next one with at least
      * average free space.
      */
     for (i = 0 ; i < bmp->db_numag; i++, agpref++) {
         if (agpref == bmp->db_numag)
             agpref = 0;
 
         if (atomic_read(&bmp->db_active[agpref]))
             /* open file is currently growing in this ag */
             continue;
         if (bmp->db_agfree[agpref] >= avgfree) {
             /* Return this one */
             bmp->db_agpref = agpref;
             goto unlock;
         } else if (bmp->db_agfree[agpref] > hwm) {
             /* Less than avg. freespace, but best so far */
             hwm = bmp->db_agfree[agpref];
             next_best = agpref;
         }
     }
 
     /*
      * If no inactive ag was found with average freespace, use the
      * next best
      */
     if (next_best != -1)
         bmp->db_agpref = next_best;
     /* else leave db_agpref unchanged */
 unlock:
     BMAP_UNLOCK(bmp);
 
     /* return the preferred group.
      */
     return (bmp->db_agpref);
 }
 
 /*
  * NAME:    dbAlloc()
  *
  * FUNCTION:    attempt to allocate a specified number of contiguous free
  *      blocks from the working allocation block map.
  *
  *      the block allocation policy uses hints and a multi-step
  *      approach.
  *
  *      for allocation requests smaller than the number of blocks
  *      per dmap, we first try to allocate the new blocks
  *      immediately following the hint.  if these blocks are not
  *      available, we try to allocate blocks near the hint.  if
  *      no blocks near the hint are available, we next try to
  *      allocate within the same dmap as contains the hint.
  *
  *      if no blocks are available in the dmap or the allocation
  *      request is larger than the dmap size, we try to allocate
  *      within the same allocation group as contains the hint. if
  *      this does not succeed, we finally try to allocate anywhere
  *      within the aggregate.
  *
  *      we also try to allocate anywhere within the aggregate
  *      for allocation requests larger than the allocation group
  *      size or requests that specify no hint value.
  *
  * PARAMETERS:
  *  ip  - pointer to in-core inode;
  *  hint    - allocation hint.
  *  nblocks - number of contiguous blocks in the range.
  *  results - on successful return, set to the starting block number
  *        of the newly allocated contiguous range.
  *
  * RETURN VALUES:
  *  0   - success
  *  -ENOSPC - insufficient disk resources
  *  -EIO    - i/o error
  */
 int dbAlloc(struct inode *ip, s64 hint, s64 nblocks, s64 * results)
 {
     int rc, agno;
     struct inode *ipbmap = JFS_SBI(ip->i_sb)->ipbmap;
     struct bmap *bmp;
     struct metapage *mp;
     s64 lblkno, blkno;
     struct dmap *dp;
     int l2nb;
     s64 mapSize;
     int writers;
 
     /* assert that nblocks is valid */
     assert(nblocks > 0);
 
     /* get the log2 number of blocks to be allocated.
      * if the number of blocks is not a log2 multiple,
      * it will be rounded up to the next log2 multiple.
      */
     l2nb = BLKSTOL2(nblocks);
 
     bmp = JFS_SBI(ip->i_sb)->bmap;
 
     mapSize = bmp->db_mapsize;
 
     /* the hint should be within the map */
     if (hint >= mapSize) {
         jfs_error(ip->i_sb, "the hint is outside the map\n");
         return -EIO;
     }
 
     /* if the number of blocks to be allocated is greater than the
      * allocation group size, try to allocate anywhere.
      */
     if (l2nb > bmp->db_agl2size) {
         IWRITE_LOCK(ipbmap, RDWRLOCK_DMAP);
 
         rc = dbAllocAny(bmp, nblocks, l2nb, results);
 
         goto write_unlock;
     }
 
     /*
      * If no hint, let dbNextAG recommend an allocation group
      */
     if (hint == 0)
         goto pref_ag;
 
     /* we would like to allocate close to the hint.  adjust the
      * hint to the block following the hint since the allocators
      * will start looking for free space starting at this point.
      */
     blkno = hint + 1;
 
     if (blkno >= bmp->db_mapsize)
         goto pref_ag;
 
     agno = blkno >> bmp->db_agl2size;
 
     /* check if blkno crosses over into a new allocation group.
      * if so, check if we should allow allocations within this
      * allocation group.
      */
     if ((blkno & (bmp->db_agsize - 1)) == 0)
         /* check if the AG is currently being written to.
          * if so, call dbNextAG() to find a non-busy
          * AG with sufficient free space.
          */
         if (atomic_read(&bmp->db_active[agno]))
             goto pref_ag;
 
     /* check if the allocation request size can be satisfied from a
      * single dmap.  if so, try to allocate from the dmap containing
      * the hint using a tiered strategy.
      */
     if (nblocks <= BPERDMAP) {
         IREAD_LOCK(ipbmap, RDWRLOCK_DMAP);
 
         /* get the buffer for the dmap containing the hint.
          */
         rc = -EIO;
         lblkno = BLKTODMAP(blkno, bmp->db_l2nbperpage);
         mp = read_metapage(ipbmap, lblkno, PSIZE, 0);
         if (mp == NULL)
             goto read_unlock;
 
         dp = (struct dmap *) mp->data;
 
         /* first, try to satisfy the allocation request with the
          * blocks beginning at the hint.
          */
         if ((rc = dbAllocNext(bmp, dp, blkno, (int) nblocks))
             != -ENOSPC) {
             if (rc == 0) {
                 *results = blkno;
                 mark_metapage_dirty(mp);
             }
 
             release_metapage(mp);
             goto read_unlock;
         }
 
         writers = atomic_read(&bmp->db_active[agno]);
         if ((writers > 1) ||
             ((writers == 1) && (JFS_IP(ip)->active_ag != agno))) {
             /*
              * Someone else is writing in this allocation
              * group.  To avoid fragmenting, try another ag
              */
             release_metapage(mp);
             IREAD_UNLOCK(ipbmap);
             goto pref_ag;
         }
 
         /* next, try to satisfy the allocation request with blocks
          * near the hint.
          */
         if ((rc =
              dbAllocNear(bmp, dp, blkno, (int) nblocks, l2nb, results))
             != -ENOSPC) {
             if (rc == 0)
                 mark_metapage_dirty(mp);
 
             release_metapage(mp);
             goto read_unlock;
         }
 
         /* try to satisfy the allocation request with blocks within
          * the same dmap as the hint.
          */
         if ((rc = dbAllocDmapLev(bmp, dp, (int) nblocks, l2nb, results))
             != -ENOSPC) {
             if (rc == 0)
                 mark_metapage_dirty(mp);
 
             release_metapage(mp);
             goto read_unlock;
         }
 
         release_metapage(mp);
         IREAD_UNLOCK(ipbmap);
     }
 
     /* try to satisfy the allocation request with blocks within
      * the same allocation group as the hint.
      */
     IWRITE_LOCK(ipbmap, RDWRLOCK_DMAP);
     if ((rc = dbAllocAG(bmp, agno, nblocks, l2nb, results)) != -ENOSPC)
         goto write_unlock;
 
     IWRITE_UNLOCK(ipbmap);
 
 
       pref_ag:
     /*
      * Let dbNextAG recommend a preferred allocation group
      */
     agno = dbNextAG(ipbmap);
     IWRITE_LOCK(ipbmap, RDWRLOCK_DMAP);
 
     /* Try to allocate within this allocation group.  if that fails, try to
      * allocate anywhere in the map.
      */
     if ((rc = dbAllocAG(bmp, agno, nblocks, l2nb, results)) == -ENOSPC)
         rc = dbAllocAny(bmp, nblocks, l2nb, results);
 
       write_unlock:
     IWRITE_UNLOCK(ipbmap);
 
     return (rc);
 
       read_unlock:
     IREAD_UNLOCK(ipbmap);
 
     return (rc);
 }
 
 /*
  * NAME:    dbReAlloc()
  *
  * FUNCTION:    attempt to extend a current allocation by a specified
  *      number of blocks.
  *
  *      this routine attempts to satisfy the allocation request
  *      by first trying to extend the existing allocation in
  *      place by allocating the additional blocks as the blocks
  *      immediately following the current allocation.  if these
  *      blocks are not available, this routine will attempt to
  *      allocate a new set of contiguous blocks large enough
  *      to cover the existing allocation plus the additional
  *      number of blocks required.
  *
  * PARAMETERS:
  *  ip      -  pointer to in-core inode requiring allocation.
  *  blkno       -  starting block of the current allocation.
  *  nblocks     -  number of contiguous blocks within the current
  *             allocation.
  *  addnblocks  -  number of blocks to add to the allocation.
  *  results -      on successful return, set to the starting block number
  *             of the existing allocation if the existing allocation
  *             was extended in place or to a newly allocated contiguous
  *             range if the existing allocation could not be extended
  *             in place.
  *
  * RETURN VALUES:
  *  0   - success
  *  -ENOSPC - insufficient disk resources
  *  -EIO    - i/o error
  */
 int
 dbReAlloc(struct inode *ip,
       s64 blkno, s64 nblocks, s64 addnblocks, s64 * results)
 {
     int rc;
 
     /* try to extend the allocation in place.
      */
     if ((rc = dbExtend(ip, blkno, nblocks, addnblocks)) == 0) {
         *results = blkno;
         return (0);
     } else {
         if (rc != -ENOSPC)
             return (rc);
     }
 
     /* could not extend the allocation in place, so allocate a
      * new set of blocks for the entire request (i.e. try to get
      * a range of contiguous blocks large enough to cover the
      * existing allocation plus the additional blocks.)
      */
     return (dbAlloc
         (ip, blkno + nblocks - 1, addnblocks + nblocks, results));
 }
 
 
 /*
  * NAME:    dbExtend()
  *
  * FUNCTION:    attempt to extend a current allocation by a specified
  *      number of blocks.
  *
  *      this routine attempts to satisfy the allocation request
  *      by first trying to extend the existing allocation in
  *      place by allocating the additional blocks as the blocks
  *      immediately following the current allocation.
  *
  * PARAMETERS:
  *  ip      -  pointer to in-core inode requiring allocation.
  *  blkno       -  starting block of the current allocation.
  *  nblocks     -  number of contiguous blocks within the current
  *             allocation.
  *  addnblocks  -  number of blocks to add to the allocation.
  *
  * RETURN VALUES:
  *  0   - success
  *  -ENOSPC - insufficient disk resources
  *  -EIO    - i/o error
  */
 static int dbExtend(struct inode *ip, s64 blkno, s64 nblocks, s64 addnblocks)
 {
     struct jfs_sb_info *sbi = JFS_SBI(ip->i_sb);
     s64 lblkno, lastblkno, extblkno;
     uint rel_block;
     struct metapage *mp;
     struct dmap *dp;
     int rc;
     struct inode *ipbmap = sbi->ipbmap;
     struct bmap *bmp;
 
     /*
      * We don't want a non-aligned extent to cross a page boundary
      */
     if (((rel_block = blkno & (sbi->nbperpage - 1))) &&
         (rel_block + nblocks + addnblocks > sbi->nbperpage))
         return -ENOSPC;
 
     /* get the last block of the current allocation */
     lastblkno = blkno + nblocks - 1;
 
     /* determine the block number of the block following
      * the existing allocation.
      */
     extblkno = lastblkno + 1;
 
     IREAD_LOCK(ipbmap, RDWRLOCK_DMAP);
 
     /* better be within the file system */
     bmp = sbi->bmap;
     if (lastblkno < 0 || lastblkno >= bmp->db_mapsize) {
         IREAD_UNLOCK(ipbmap);
         jfs_error(ip->i_sb, "the block is outside the filesystem\n");
         return -EIO;
     }
 
     /* we'll attempt to extend the current allocation in place by
      * allocating the additional blocks as the blocks immediately
      * following the current allocation.  we only try to extend the
      * current allocation in place if the number of additional blocks
      * can fit into a dmap, the last block of the current allocation
      * is not the last block of the file system, and the start of the
      * inplace extension is not on an allocation group boundary.
      */
     if (addnblocks > BPERDMAP || extblkno >= bmp->db_mapsize ||
         (extblkno & (bmp->db_agsize - 1)) == 0) {
         IREAD_UNLOCK(ipbmap);
         return -ENOSPC;
     }
 
     /* get the buffer for the dmap containing the first block
      * of the extension.
      */
     lblkno = BLKTODMAP(extblkno, bmp->db_l2nbperpage);
     mp = read_metapage(ipbmap, lblkno, PSIZE, 0);
     if (mp == NULL) {
         IREAD_UNLOCK(ipbmap);
         return -EIO;
     }
 
     dp = (struct dmap *) mp->data;
 
     /* try to allocate the blocks immediately following the
      * current allocation.
      */
     rc = dbAllocNext(bmp, dp, extblkno, (int) addnblocks);
 
     IREAD_UNLOCK(ipbmap);
 
     /* were we successful ? */
     if (rc == 0)
         write_metapage(mp);
     else
         /* we were not successful */
         release_metapage(mp);
 
     return (rc);
 }
 
 
 /*
  * NAME:    dbAllocNext()
  *
  * FUNCTION:    attempt to allocate the blocks of the specified block
  *      range within a dmap.
  *
  * PARAMETERS:
  *  bmp -  pointer to bmap descriptor
  *  dp  -  pointer to dmap.
  *  blkno   -  starting block number of the range.
  *  nblocks -  number of contiguous free blocks of the range.
  *
  * RETURN VALUES:
  *  0   - success
  *  -ENOSPC - insufficient disk resources
  *  -EIO    - i/o error
  *
  * serialization: IREAD_LOCK(ipbmap) held on entry/exit;
  */
 static int dbAllocNext(struct bmap * bmp, struct dmap * dp, s64 blkno,
                int nblocks)
 {
     int dbitno, word, rembits, nb, nwords, wbitno, nw;
     int l2size;
     s8 *leaf;
     u32 mask;
 
     if (dp->tree.leafidx != cpu_to_le32(LEAFIND)) {
         jfs_error(bmp->db_ipbmap->i_sb, "Corrupt dmap page\n");
         return -EIO;
     }
 
     /* pick up a pointer to the leaves of the dmap tree.
      */
     leaf = dp->tree.stree + le32_to_cpu(dp->tree.leafidx);
 
     /* determine the bit number and word within the dmap of the
      * starting block.
      */
     dbitno = blkno & (BPERDMAP - 1);
     word = dbitno >> L2DBWORD;
 
     /* check if the specified block range is contained within
      * this dmap.
      */
     if (dbitno + nblocks > BPERDMAP)
         return -ENOSPC;
 
     /* check if the starting leaf indicates that anything
      * is free.
      */
     if (leaf[word] == NOFREE)
         return -ENOSPC;
 
     /* check the dmaps words corresponding to block range to see
      * if the block range is free.  not all bits of the first and
      * last words may be contained within the block range.  if this
      * is the case, we'll work against those words (i.e. partial first
      * and/or last) on an individual basis (a single pass) and examine
      * the actual bits to determine if they are free.  a single pass
      * will be used for all dmap words fully contained within the
      * specified range.  within this pass, the leaves of the dmap
      * tree will be examined to determine if the blocks are free. a
      * single leaf may describe the free space of multiple dmap
      * words, so we may visit only a subset of the actual leaves
      * corresponding to the dmap words of the block range.
      */
     for (rembits = nblocks; rembits > 0; rembits -= nb, dbitno += nb) {
         /* determine the bit number within the word and
          * the number of bits within the word.
          */
         wbitno = dbitno & (DBWORD - 1);
         nb = min(rembits, DBWORD - wbitno);
 
         /* check if only part of the word is to be examined.
          */
         if (nb < DBWORD) {
             /* check if the bits are free.
              */
             mask = (ONES << (DBWORD - nb) >> wbitno);
             if ((mask & ~le32_to_cpu(dp->wmap[word])) != mask)
                 return -ENOSPC;
 
             word += 1;
         } else {
             /* one or more dmap words are fully contained
              * within the block range.  determine how many
              * words and how many bits.
              */
             nwords = rembits >> L2DBWORD;
             nb = nwords << L2DBWORD;
 
             /* now examine the appropriate leaves to determine
              * if the blocks are free.
              */
             while (nwords > 0) {
                 /* does the leaf describe any free space ?
                  */
                 if (leaf[word] < BUDMIN)
                     return -ENOSPC;
 
                 /* determine the l2 number of bits provided
                  * by this leaf.
                  */
                 l2size =
                     min_t(int, leaf[word], NLSTOL2BSZ(nwords));
 
                 /* determine how many words were handled.
                  */
                 nw = BUDSIZE(l2size, BUDMIN);
 
                 nwords -= nw;
                 word += nw;
             }
         }
     }
 
     /* allocate the blocks.
      */
     return (dbAllocDmap(bmp, dp, blkno, nblocks));
 }
 
 
 /*
  * NAME:    dbAllocNear()
  *
  * FUNCTION:    attempt to allocate a number of contiguous free blocks near
  *      a specified block (hint) within a dmap.
  *
  *      starting with the dmap leaf that covers the hint, we'll
  *      check the next four contiguous leaves for sufficient free
  *      space.  if sufficient free space is found, we'll allocate
  *      the desired free space.
  *
  * PARAMETERS:
  *  bmp -  pointer to bmap descriptor
  *  dp  -  pointer to dmap.
  *  blkno   -  block number to allocate near.
  *  nblocks -  actual number of contiguous free blocks desired.
  *  l2nb    -  log2 number of contiguous free blocks desired.
  *  results -  on successful return, set to the starting block number
  *         of the newly allocated range.
  *
  * RETURN VALUES:
  *  0   - success
  *  -ENOSPC - insufficient disk resources
  *  -EIO    - i/o error
  *
  * serialization: IREAD_LOCK(ipbmap) held on entry/exit;
  */
 static int
 dbAllocNear(struct bmap * bmp,
         struct dmap * dp, s64 blkno, int nblocks, int l2nb, s64 * results)
 {
     int word, lword, rc;
     s8 *leaf;
 
     if (dp->tree.leafidx != cpu_to_le32(LEAFIND)) {
         jfs_error(bmp->db_ipbmap->i_sb, "Corrupt dmap page\n");
         return -EIO;
     }
 
     leaf = dp->tree.stree + le32_to_cpu(dp->tree.leafidx);
 
     /* determine the word within the dmap that holds the hint
      * (i.e. blkno).  also, determine the last word in the dmap
      * that we'll include in our examination.
      */
     word = (blkno & (BPERDMAP - 1)) >> L2DBWORD;
     lword = min(word + 4, LPERDMAP);
 
     /* examine the leaves for sufficient free space.
      */
     for (; word < lword; word++) {
         /* does the leaf describe sufficient free space ?
          */
         if (leaf[word] < l2nb)
             continue;
 
         /* determine the block number within the file system
          * of the first block described by this dmap word.
          */
         blkno = le64_to_cpu(dp->start) + (word << L2DBWORD);
 
         /* if not all bits of the dmap word are free, get the
          * starting bit number within the dmap word of the required
          * string of free bits and adjust the block number with the
          * value.
          */
         if (leaf[word] < BUDMIN)
             blkno +=
                 dbFindBits(le32_to_cpu(dp->wmap[word]), l2nb);
 
         /* allocate the blocks.
          */
         if ((rc = dbAllocDmap(bmp, dp, blkno, nblocks)) == 0)
             *results = blkno;
 
         return (rc);
     }
 
     return -ENOSPC;
 }
 
 
 /*
  * NAME:    dbAllocAG()
  *
  * FUNCTION:    attempt to allocate the specified number of contiguous
  *      free blocks within the specified allocation group.
  *
  *      unless the allocation group size is equal to the number
  *      of blocks per dmap, the dmap control pages will be used to
  *      find the required free space, if available.  we start the
  *      search at the highest dmap control page level which
  *      distinctly describes the allocation group's free space
  *      (i.e. the highest level at which the allocation group's
  *      free space is not mixed in with that of any other group).
  *      in addition, we start the search within this level at a
  *      height of the dmapctl dmtree at which the nodes distinctly
  *      describe the allocation group's free space.  at this height,
  *      the allocation group's free space may be represented by 1
  *      or two sub-trees, depending on the allocation group size.
  *      we search the top nodes of these subtrees left to right for
  *      sufficient free space.  if sufficient free space is found,
  *      the subtree is searched to find the leftmost leaf that
  *      has free space.  once we have made it to the leaf, we
  *      move the search to the next lower level dmap control page
  *      corresponding to this leaf.  we continue down the dmap control
  *      pages until we find the dmap that contains or starts the
  *      sufficient free space and we allocate at this dmap.
  *
  *      if the allocation group size is equal to the dmap size,
  *      we'll start at the dmap corresponding to the allocation
  *      group and attempt the allocation at this level.
  *
  *      the dmap control page search is also not performed if the
  *      allocation group is completely free and we go to the first
  *      dmap of the allocation group to do the allocation.  this is
  *      done because the allocation group may be part (not the first
  *      part) of a larger binary buddy system, causing the dmap
  *      control pages to indicate no free space (NOFREE) within
  *      the allocation group.
  *
  * PARAMETERS:
  *  bmp -  pointer to bmap descriptor
  *  agno    - allocation group number.
  *  nblocks -  actual number of contiguous free blocks desired.
  *  l2nb    -  log2 number of contiguous free blocks desired.
  *  results -  on successful return, set to the starting block number
  *         of the newly allocated range.
  *
  * RETURN VALUES:
  *  0   - success
  *  -ENOSPC - insufficient disk resources
  *  -EIO    - i/o error
  *
  * note: IWRITE_LOCK(ipmap) held on entry/exit;
  */
 static int
 dbAllocAG(struct bmap * bmp, int agno, s64 nblocks, int l2nb, s64 * results)
 {
     struct metapage *mp;
     struct dmapctl *dcp;
     int rc, ti, i, k, m, n, agperlev;
     s64 blkno, lblkno;
     int budmin;
 
     /* allocation request should not be for more than the
      * allocation group size.
      */
     if (l2nb > bmp->db_agl2size) {
         jfs_error(bmp->db_ipbmap->i_sb,
               "allocation request is larger than the allocation group size\n");
         return -EIO;
     }
 
     /* determine the starting block number of the allocation
      * group.
      */
     blkno = (s64) agno << bmp->db_agl2size;
 
     /* check if the allocation group size is the minimum allocation
      * group size or if the allocation group is completely free. if
      * the allocation group size is the minimum size of BPERDMAP (i.e.
      * 1 dmap), there is no need to search the dmap control page (below)
      * that fully describes the allocation group since the allocation
      * group is already fully described by a dmap.  in this case, we
      * just call dbAllocCtl() to search the dmap tree and allocate the
      * required space if available.
      *
      * if the allocation group is completely free, dbAllocCtl() is
      * also called to allocate the required space.  this is done for
      * two reasons.  first, it makes no sense searching the dmap control
      * pages for free space when we know that free space exists.  second,
      * the dmap control pages may indicate that the allocation group
      * has no free space if the allocation group is part (not the first
      * part) of a larger binary buddy system.
      */
     if (bmp->db_agsize == BPERDMAP
         || bmp->db_agfree[agno] == bmp->db_agsize) {
         rc = dbAllocCtl(bmp, nblocks, l2nb, blkno, results);
         if ((rc == -ENOSPC) &&
             (bmp->db_agfree[agno] == bmp->db_agsize)) {
             printk(KERN_ERR "blkno = %Lx, blocks = %Lx\n",
                    (unsigned long long) blkno,
                    (unsigned long long) nblocks);
             jfs_error(bmp->db_ipbmap->i_sb,
                   "dbAllocCtl failed in free AG\n");
         }
         return (rc);
     }
 
     /* the buffer for the dmap control page that fully describes the
      * allocation group.
      */
     lblkno = BLKTOCTL(blkno, bmp->db_l2nbperpage, bmp->db_aglevel);
     mp = read_metapage(bmp->db_ipbmap, lblkno, PSIZE, 0);
     if (mp == NULL)
         return -EIO;
     dcp = (struct dmapctl *) mp->data;
     budmin = dcp->budmin;
 
     if (dcp->leafidx != cpu_to_le32(CTLLEAFIND)) {
         jfs_error(bmp->db_ipbmap->i_sb, "Corrupt dmapctl page\n");
         release_metapage(mp);
         return -EIO;
     }
 
     /* search the subtree(s) of the dmap control page that describes
      * the allocation group, looking for sufficient free space.  to begin,
      * determine how many allocation groups are represented in a dmap
      * control page at the control page level (i.e. L0, L1, L2) that
      * fully describes an allocation group. next, determine the starting
      * tree index of this allocation group within the control page.
      */
     agperlev =
         (1 << (L2LPERCTL - (bmp->db_agheight << 1))) / bmp->db_agwidth;
     ti = bmp->db_agstart + bmp->db_agwidth * (agno & (agperlev - 1));
 
     /* dmap control page trees fan-out by 4 and a single allocation
      * group may be described by 1 or 2 subtrees within the ag level
      * dmap control page, depending upon the ag size. examine the ag's
      * subtrees for sufficient free space, starting with the leftmost
      * subtree.
      */
     for (i = 0; i < bmp->db_agwidth; i++, ti++) {
         /* is there sufficient free space ?
          */
         if (l2nb > dcp->stree[ti])
             continue;
 
         /* sufficient free space found in a subtree. now search down
          * the subtree to find the leftmost leaf that describes this
          * free space.
          */
         for (k = bmp->db_agheight; k > 0; k--) {
             for (n = 0, m = (ti << 2) + 1; n < 4; n++) {
                 if (l2nb <= dcp->stree[m + n]) {
                     ti = m + n;
                     break;
                 }
             }
             if (n == 4) {
                 jfs_error(bmp->db_ipbmap->i_sb,
                       "failed descending stree\n");
                 release_metapage(mp);
                 return -EIO;
             }
         }
 
         /* determine the block number within the file system
          * that corresponds to this leaf.
          */
         if (bmp->db_aglevel == 2)
             blkno = 0;
         else if (bmp->db_aglevel == 1)
             blkno &= ~(MAXL1SIZE - 1);
         else        /* bmp->db_aglevel == 0 */
             blkno &= ~(MAXL0SIZE - 1);
 
         blkno +=
             ((s64) (ti - le32_to_cpu(dcp->leafidx))) << budmin;
 
         /* release the buffer in preparation for going down
          * the next level of dmap control pages.
          */
         release_metapage(mp);
 
         /* check if we need to continue to search down the lower
          * level dmap control pages.  we need to if the number of
          * blocks required is less than maximum number of blocks
          * described at the next lower level.
          */
         if (l2nb < budmin) {
 
             /* search the lower level dmap control pages to get
              * the starting block number of the dmap that
              * contains or starts off the free space.
              */
             if ((rc =
                  dbFindCtl(bmp, l2nb, bmp->db_aglevel - 1,
                        &blkno))) {
                 if (rc == -ENOSPC) {
                     jfs_error(bmp->db_ipbmap->i_sb,
                           "control page inconsistent\n");
                     return -EIO;
                 }
                 return (rc);
             }
         }
 
         /* allocate the blocks.
          */
         rc = dbAllocCtl(bmp, nblocks, l2nb, blkno, results);
         if (rc == -ENOSPC) {
             jfs_error(bmp->db_ipbmap->i_sb,
                   "unable to allocate blocks\n");
             rc = -EIO;
         }
         return (rc);
     }
 
     /* no space in the allocation group.  release the buffer and
      * return -ENOSPC.
      */
     release_metapage(mp);
 
     return -ENOSPC;
 }
 
 
 /*
  * NAME:    dbAllocAny()
  *
  * FUNCTION:    attempt to allocate the specified number of contiguous
  *      free blocks anywhere in the file system.
  *
  *      dbAllocAny() attempts to find the sufficient free space by
  *      searching down the dmap control pages, starting with the
  *      highest level (i.e. L0, L1, L2) control page.  if free space
  *      large enough to satisfy the desired free space is found, the
  *      desired free space is allocated.
  *
  * PARAMETERS:
  *  bmp -  pointer to bmap descriptor
  *  nblocks  -  actual number of contiguous free blocks desired.
  *  l2nb     -  log2 number of contiguous free blocks desired.
  *  results -  on successful return, set to the starting block number
  *         of the newly allocated range.
  *
  * RETURN VALUES:
  *  0   - success
  *  -ENOSPC - insufficient disk resources
  *  -EIO    - i/o error
  *
  * serialization: IWRITE_LOCK(ipbmap) held on entry/exit;
  */
 static int dbAllocAny(struct bmap * bmp, s64 nblocks, int l2nb, s64 * results)
 {
     int rc;
     s64 blkno = 0;
 
     /* starting with the top level dmap control page, search
      * down the dmap control levels for sufficient free space.
      * if free space is found, dbFindCtl() returns the starting
      * block number of the dmap that contains or starts off the
      * range of free space.
      */
     if ((rc = dbFindCtl(bmp, l2nb, bmp->db_maxlevel, &blkno)))
         return (rc);
 
     /* allocate the blocks.
      */
     rc = dbAllocCtl(bmp, nblocks, l2nb, blkno, results);
     if (rc == -ENOSPC) {
         jfs_error(bmp->db_ipbmap->i_sb, "unable to allocate blocks\n");
         return -EIO;
     }
     return (rc);
 }
 
 
 /*
  * NAME:    dbDiscardAG()
  *
  * FUNCTION:    attempt to discard (TRIM) all free blocks of specific AG
  *
  *      algorithm:
  *      1) allocate blocks, as large as possible and save them
  *         while holding IWRITE_LOCK on ipbmap
  *      2) trim all these saved block/length values
  *      3) mark the blocks free again
  *
  *      benefit:
  *      - we work only on one ag at some time, minimizing how long we
  *        need to lock ipbmap
  *      - reading / writing the fs is possible most time, even on
  *        trimming
  *
  *      downside:
  *      - we write two times to the dmapctl and dmap pages
  *      - but for me, this seems the best way, better ideas?
  *      /TR 2012
  *
  * PARAMETERS:
  *  ip  - pointer to in-core inode
  *  agno    - ag to trim
  *  minlen  - minimum value of contiguous blocks
  *
  * RETURN VALUES:
  *  s64 - actual number of blocks trimmed
  */
 s64 dbDiscardAG(struct inode *ip, int agno, s64 minlen)
 {
     struct inode *ipbmap = JFS_SBI(ip->i_sb)->ipbmap;
     struct bmap *bmp = JFS_SBI(ip->i_sb)->bmap;
     s64 nblocks, blkno;
     u64 trimmed = 0;
     int rc, l2nb;
     struct super_block *sb = ipbmap->i_sb;
 
     struct range2trim {
         u64 blkno;
         u64 nblocks;
     } *totrim, *tt;
 
     /* max blkno / nblocks pairs to trim */
     int count = 0, range_cnt;
     u64 max_ranges;
 
     /* prevent others from writing new stuff here, while trimming */
     IWRITE_LOCK(ipbmap, RDWRLOCK_DMAP);
 
     nblocks = bmp->db_agfree[agno];
     max_ranges = nblocks;
     do_div(max_ranges, minlen);
     range_cnt = min_t(u64, max_ranges + 1, 32 * 1024);
     totrim = kmalloc_array(range_cnt, sizeof(struct range2trim), GFP_NOFS);
     if (totrim == NULL) {
         jfs_error(bmp->db_ipbmap->i_sb, "no memory for trim array\n");
         IWRITE_UNLOCK(ipbmap);
         return 0;
     }
 
     tt = totrim;
     while (nblocks >= minlen) {
         l2nb = BLKSTOL2(nblocks);
 
         /* 0 = okay, -EIO = fatal, -ENOSPC -> try smaller block */
         rc = dbAllocAG(bmp, agno, nblocks, l2nb, &blkno);
         if (rc == 0) {
             tt->blkno = blkno;
             tt->nblocks = nblocks;
             tt++; count++;
 
             /* the whole ag is free, trim now */
             if (bmp->db_agfree[agno] == 0)
                 break;
 
             /* give a hint for the next while */
             nblocks = bmp->db_agfree[agno];
             continue;
         } else if (rc == -ENOSPC) {
             /* search for next smaller log2 block */
             l2nb = BLKSTOL2(nblocks) - 1;
             nblocks = 1LL << l2nb;
         } else {
             /* Trim any already allocated blocks */
             jfs_error(bmp->db_ipbmap->i_sb, "-EIO\n");
             break;
         }
 
         /* check, if our trim array is full */
         if (unlikely(count >= range_cnt - 1))
             break;
     }
     IWRITE_UNLOCK(ipbmap);
 
     tt->nblocks = 0; /* mark the current end */
     for (tt = totrim; tt->nblocks != 0; tt++) {
         /* when mounted with online discard, dbFree() will
          * call jfs_issue_discard() itself */
         if (!(JFS_SBI(sb)->flag & JFS_DISCARD))
             jfs_issue_discard(ip, tt->blkno, tt->nblocks);
         dbFree(ip, tt->blkno, tt->nblocks);
         trimmed += tt->nblocks;
     }
     kfree(totrim);
 
     return trimmed;
 }
 
 /*
  * NAME:    dbFindCtl()
  *
  * FUNCTION:    starting at a specified dmap control page level and block
  *      number, search down the dmap control levels for a range of
  *      contiguous free blocks large enough to satisfy an allocation
  *      request for the specified number of free blocks.
  *
  *      if sufficient contiguous free blocks are found, this routine
  *      returns the starting block number within a dmap page that
  *      contains or starts a range of contiqious free blocks that
  *      is sufficient in size.
  *
  * PARAMETERS:
  *  bmp -  pointer to bmap descriptor
  *  level   -  starting dmap control page level.
  *  l2nb    -  log2 number of contiguous free blocks desired.
  *  *blkno  -  on entry, starting block number for conducting the search.
  *         on successful return, the first block within a dmap page
  *         that contains or starts a range of contiguous free blocks.
  *
  * RETURN VALUES:
  *  0   - success
  *  -ENOSPC - insufficient disk resources
  *  -EIO    - i/o error
  *
  * serialization: IWRITE_LOCK(ipbmap) held on entry/exit;
  */
 static int dbFindCtl(struct bmap * bmp, int l2nb, int level, s64 * blkno)
 {
     int rc, leafidx, lev;
     s64 b, lblkno;
     struct dmapctl *dcp;
     int budmin;
     struct metapage *mp;
 
     /* starting at the specified dmap control page level and block
      * number, search down the dmap control levels for the starting
      * block number of a dmap page that contains or starts off
      * sufficient free blocks.
      */
     for (lev = level, b = *blkno; lev >= 0; lev--) {
         /* get the buffer of the dmap control page for the block
          * number and level (i.e. L0, L1, L2).
          */
         lblkno = BLKTOCTL(b, bmp->db_l2nbperpage, lev);
         mp = read_metapage(bmp->db_ipbmap, lblkno, PSIZE, 0);
         if (mp == NULL)
             return -EIO;
         dcp = (struct dmapctl *) mp->data;
         budmin = dcp->budmin;
 
         if (dcp->leafidx != cpu_to_le32(CTLLEAFIND)) {
             jfs_error(bmp->db_ipbmap->i_sb,
                   "Corrupt dmapctl page\n");
             release_metapage(mp);
             return -EIO;
         }
 
         /* search the tree within the dmap control page for
          * sufficient free space.  if sufficient free space is found,
          * dbFindLeaf() returns the index of the leaf at which
          * free space was found.
          */
         rc = dbFindLeaf((dmtree_t *) dcp, l2nb, &leafidx);
 
         /* release the buffer.
          */
         release_metapage(mp);
 
         /* space found ?
          */
         if (rc) {
             if (lev != level) {
                 jfs_error(bmp->db_ipbmap->i_sb,
                       "dmap inconsistent\n");
                 return -EIO;
             }
             return -ENOSPC;
         }
 
         /* adjust the block number to reflect the location within
          * the dmap control page (i.e. the leaf) at which free
          * space was found.
          */
         b += (((s64) leafidx) << budmin);
 
         /* we stop the search at this dmap control page level if
          * the number of blocks required is greater than or equal
          * to the maximum number of blocks described at the next
          * (lower) level.
          */
         if (l2nb >= budmin)
             break;
     }
 
     *blkno = b;
     return (0);
 }
 
 
 /*
  * NAME:    dbAllocCtl()
  *
  * FUNCTION:    attempt to allocate a specified number of contiguous
  *      blocks starting within a specific dmap.
  *
  *      this routine is called by higher level routines that search
  *      the dmap control pages above the actual dmaps for contiguous
  *      free space.  the result of successful searches by these
  *      routines are the starting block numbers within dmaps, with
  *      the dmaps themselves containing the desired contiguous free
  *      space or starting a contiguous free space of desired size
  *      that is made up of the blocks of one or more dmaps. these
  *      calls should not fail due to insufficent resources.
  *
  *      this routine is called in some cases where it is not known
  *      whether it will fail due to insufficient resources.  more
  *      specifically, this occurs when allocating from an allocation
  *      group whose size is equal to the number of blocks per dmap.
  *      in this case, the dmap control pages are not examined prior
  *      to calling this routine (to save pathlength) and the call
  *      might fail.
  *
  *      for a request size that fits within a dmap, this routine relies
  *      upon the dmap's dmtree to find the requested contiguous free
  *      space.  for request sizes that are larger than a dmap, the
  *      requested free space will start at the first block of the
  *      first dmap (i.e. blkno).
  *
  * PARAMETERS:
  *  bmp -  pointer to bmap descriptor
  *  nblocks  -  actual number of contiguous free blocks to allocate.
  *  l2nb     -  log2 number of contiguous free blocks to allocate.
  *  blkno    -  starting block number of the dmap to start the allocation
  *          from.
  *  results -  on successful return, set to the starting block number
  *         of the newly allocated range.
  *
  * RETURN VALUES:
  *  0   - success
  *  -ENOSPC - insufficient disk resources
  *  -EIO    - i/o error
  *
  * serialization: IWRITE_LOCK(ipbmap) held on entry/exit;
  */
 static int
 dbAllocCtl(struct bmap * bmp, s64 nblocks, int l2nb, s64 blkno, s64 * results)
 {
     int rc, nb;
     s64 b, lblkno, n;
     struct metapage *mp;
     struct dmap *dp;
 
     /* check if the allocation request is confined to a single dmap.
      */
     if (l2nb <= L2BPERDMAP) {
         /* get the buffer for the dmap.
          */
         lblkno = BLKTODMAP(blkno, bmp->db_l2nbperpage);
         mp = read_metapage(bmp->db_ipbmap, lblkno, PSIZE, 0);
         if (mp == NULL)
             return -EIO;
         dp = (struct dmap *) mp->data;
 
         /* try to allocate the blocks.
          */
         rc = dbAllocDmapLev(bmp, dp, (int) nblocks, l2nb, results);
         if (rc == 0)
             mark_metapage_dirty(mp);
 
         release_metapage(mp);
 
         return (rc);
     }
 
     /* allocation request involving multiple dmaps. it must start on
      * a dmap boundary.
      */
     assert((blkno & (BPERDMAP - 1)) == 0);
 
     /* allocate the blocks dmap by dmap.
      */
     for (n = nblocks, b = blkno; n > 0; n -= nb, b += nb) {
         /* get the buffer for the dmap.
          */
         lblkno = BLKTODMAP(b, bmp->db_l2nbperpage);
         mp = read_metapage(bmp->db_ipbmap, lblkno, PSIZE, 0);
         if (mp == NULL) {
             rc = -EIO;
             goto backout;
         }
         dp = (struct dmap *) mp->data;
 
         /* the dmap better be all free.
          */
         if (dp->tree.stree[ROOT] != L2BPERDMAP) {
             release_metapage(mp);
             jfs_error(bmp->db_ipbmap->i_sb,
                   "the dmap is not all free\n");
             rc = -EIO;
             goto backout;
         }
 
         /* determine how many blocks to allocate from this dmap.
          */
         nb = min_t(s64, n, BPERDMAP);
 
         /* allocate the blocks from the dmap.
          */
         if ((rc = dbAllocDmap(bmp, dp, b, nb))) {
             release_metapage(mp);
             goto backout;
         }
 
         /* write the buffer.
          */
         write_metapage(mp);
     }
 
     /* set the results (starting block number) and return.
      */
     *results = blkno;
     return (0);
 
     /* something failed in handling an allocation request involving
      * multiple dmaps.  we'll try to clean up by backing out any
      * allocation that has already happened for this request.  if
      * we fail in backing out the allocation, we'll mark the file
      * system to indicate that blocks have been leaked.
      */
       backout:
 
     /* try to backout the allocations dmap by dmap.
      */
     for (n = nblocks - n, b = blkno; n > 0;
          n -= BPERDMAP, b += BPERDMAP) {
         /* get the buffer for this dmap.
          */
         lblkno = BLKTODMAP(b, bmp->db_l2nbperpage);
         mp = read_metapage(bmp->db_ipbmap, lblkno, PSIZE, 0);
         if (mp == NULL) {
             /* could not back out.  mark the file system
              * to indicate that we have leaked blocks.
              */
             jfs_error(bmp->db_ipbmap->i_sb,
                   "I/O Error: Block Leakage\n");
             continue;
         }
         dp = (struct dmap *) mp->data;
 
         /* free the blocks is this dmap.
          */
         if (dbFreeDmap(bmp, dp, b, BPERDMAP)) {
             /* could not back out.  mark the file system
              * to indicate that we have leaked blocks.
              */
             release_metapage(mp);
             jfs_error(bmp->db_ipbmap->i_sb, "Block Leakage\n");
             continue;
         }
 
         /* write the buffer.
          */
         write_metapage(mp);
     }
 
     return (rc);
 }
 
 
 /*
  * NAME:    dbAllocDmapLev()
  *
  * FUNCTION:    attempt to allocate a specified number of contiguous blocks
  *      from a specified dmap.
  *
  *      this routine checks if the contiguous blocks are available.
  *      if so, nblocks of blocks are allocated; otherwise, ENOSPC is
  *      returned.
  *
  * PARAMETERS:
  *  mp  -  pointer to bmap descriptor
  *  dp  -  pointer to dmap to attempt to allocate blocks from.
  *  l2nb    -  log2 number of contiguous block desired.
  *  nblocks -  actual number of contiguous block desired.
  *  results -  on successful return, set to the starting block number
  *         of the newly allocated range.
  *
  * RETURN VALUES:
  *  0   - success
  *  -ENOSPC - insufficient disk resources
  *  -EIO    - i/o error
  *
  * serialization: IREAD_LOCK(ipbmap), e.g., from dbAlloc(), or
  *  IWRITE_LOCK(ipbmap), e.g., dbAllocCtl(), held on entry/exit;
  */
 static int
 dbAllocDmapLev(struct bmap * bmp,
            struct dmap * dp, int nblocks, int l2nb, s64 * results)
 {
     s64 blkno;
     int leafidx, rc;
 
     /* can't be more than a dmaps worth of blocks */
     assert(l2nb <= L2BPERDMAP);
 
     /* search the tree within the dmap page for sufficient
      * free space.  if sufficient free space is found, dbFindLeaf()
      * returns the index of the leaf at which free space was found.
      */
     if (dbFindLeaf((dmtree_t *) & dp->tree, l2nb, &leafidx))
         return -ENOSPC;
 
     /* determine the block number within the file system corresponding
      * to the leaf at which free space was found.
      */
     blkno = le64_to_cpu(dp->start) + (leafidx << L2DBWORD);
 
     /* if not all bits of the dmap word are free, get the starting
      * bit number within the dmap word of the required string of free
      * bits and adjust the block number with this value.
      */
     if (dp->tree.stree[leafidx + LEAFIND] < BUDMIN)
         blkno += dbFindBits(le32_to_cpu(dp->wmap[leafidx]), l2nb);
 
     /* allocate the blocks */
     if ((rc = dbAllocDmap(bmp, dp, blkno, nblocks)) == 0)
         *results = blkno;
 
     return (rc);
 }
 
 
 /*
  * NAME:    dbAllocDmap()
  *
  * FUNCTION:    adjust the disk allocation map to reflect the allocation
  *      of a specified block range within a dmap.
  *
  *      this routine allocates the specified blocks from the dmap
  *      through a call to dbAllocBits(). if the allocation of the
  *      block range causes the maximum string of free blocks within
  *      the dmap to change (i.e. the value of the root of the dmap's
  *      dmtree), this routine will cause this change to be reflected
  *      up through the appropriate levels of the dmap control pages
  *      by a call to dbAdjCtl() for the L0 dmap control page that
  *      covers this dmap.
  *
  * PARAMETERS:
  *  bmp -  pointer to bmap descriptor
  *  dp  -  pointer to dmap to allocate the block range from.
  *  blkno   -  starting block number of the block to be allocated.
  *  nblocks -  number of blocks to be allocated.
  *
  * RETURN VALUES:
  *  0   - success
  *  -EIO    - i/o error
  *
  * serialization: IREAD_LOCK(ipbmap) or IWRITE_LOCK(ipbmap) held on entry/exit;
  */
 static int dbAllocDmap(struct bmap * bmp, struct dmap * dp, s64 blkno,
                int nblocks)
 {
     s8 oldroot;
     int rc;
 
     /* save the current value of the root (i.e. maximum free string)
      * of the dmap tree.
      */
     oldroot = dp->tree.stree[ROOT];
 
     /* allocate the specified (blocks) bits */
     dbAllocBits(bmp, dp, blkno, nblocks);
 
     /* if the root has not changed, done. */
     if (dp->tree.stree[ROOT] == oldroot)
         return (0);
 
     /* root changed. bubble the change up to the dmap control pages.
      * if the adjustment of the upper level control pages fails,
      * backout the bit allocation (thus making everything consistent).
      */
     if ((rc = dbAdjCtl(bmp, blkno, dp->tree.stree[ROOT], 1, 0)))
         dbFreeBits(bmp, dp, blkno, nblocks);
 
     return (rc);
 }
 
 
 /*
  * NAME:    dbFreeDmap()
  *
  * FUNCTION:    adjust the disk allocation map to reflect the allocation
  *      of a specified block range within a dmap.
  *
  *      this routine frees the specified blocks from the dmap through
  *      a call to dbFreeBits(). if the deallocation of the block range
  *      causes the maximum string of free blocks within the dmap to
  *      change (i.e. the value of the root of the dmap's dmtree), this
  *      routine will cause this change to be reflected up through the
  *      appropriate levels of the dmap control pages by a call to
  *      dbAdjCtl() for the L0 dmap control page that covers this dmap.
  *
  * PARAMETERS:
  *  bmp -  pointer to bmap descriptor
  *  dp  -  pointer to dmap to free the block range from.
  *  blkno   -  starting block number of the block to be freed.
  *  nblocks -  number of blocks to be freed.
  *
  * RETURN VALUES:
  *  0   - success
  *  -EIO    - i/o error
  *
  * serialization: IREAD_LOCK(ipbmap) or IWRITE_LOCK(ipbmap) held on entry/exit;
  */
 static int dbFreeDmap(struct bmap * bmp, struct dmap * dp, s64 blkno,
               int nblocks)
 {
     s8 oldroot;
     int rc = 0, word;
 
     /* save the current value of the root (i.e. maximum free string)
      * of the dmap tree.
      */
     oldroot = dp->tree.stree[ROOT];
 
     /* free the specified (blocks) bits */
     rc = dbFreeBits(bmp, dp, blkno, nblocks);
 
     /* if error or the root has not changed, done. */
     if (rc || (dp->tree.stree[ROOT] == oldroot))
         return (rc);
 
     /* root changed. bubble the change up to the dmap control pages.
      * if the adjustment of the upper level control pages fails,
      * backout the deallocation.
      */
     if ((rc = dbAdjCtl(bmp, blkno, dp->tree.stree[ROOT], 0, 0))) {
         word = (blkno & (BPERDMAP - 1)) >> L2DBWORD;
 
         /* as part of backing out the deallocation, we will have
          * to back split the dmap tree if the deallocation caused
          * the freed blocks to become part of a larger binary buddy
          * system.
          */
         if (dp->tree.stree[word] == NOFREE)
             dbBackSplit((dmtree_t *) & dp->tree, word);
 
         dbAllocBits(bmp, dp, blkno, nblocks);
     }
 
     return (rc);
 }
 
 
 /*
  * NAME:    dbAllocBits()
  *
  * FUNCTION:    allocate a specified block range from a dmap.
  *
  *      this routine updates the dmap to reflect the working
  *      state allocation of the specified block range. it directly
  *      updates the bits of the working map and causes the adjustment
  *      of the binary buddy system described by the dmap's dmtree
  *      leaves to reflect the bits allocated.  it also causes the
  *      dmap's dmtree, as a whole, to reflect the allocated range.
  *
  * PARAMETERS:
  *  bmp -  pointer to bmap descriptor
  *  dp  -  pointer to dmap to allocate bits from.
  *  blkno   -  starting block number of the bits to be allocated.
  *  nblocks -  number of bits to be allocated.
  *
  * RETURN VALUES: none
  *
  * serialization: IREAD_LOCK(ipbmap) or IWRITE_LOCK(ipbmap) held on entry/exit;
  */
 static void dbAllocBits(struct bmap * bmp, struct dmap * dp, s64 blkno,
             int nblocks)
 {
     int dbitno, word, rembits, nb, nwords, wbitno, nw, agno;
     dmtree_t *tp = (dmtree_t *) & dp->tree;
     int size;
     s8 *leaf;
 
     /* pick up a pointer to the leaves of the dmap tree */
     leaf = dp->tree.stree + LEAFIND;
 
     /* determine the bit number and word within the dmap of the
      * starting block.
      */
     dbitno = blkno & (BPERDMAP - 1);
     word = dbitno >> L2DBWORD;
 
     /* block range better be within the dmap */
     assert(dbitno + nblocks <= BPERDMAP);
 
     /* allocate the bits of the dmap's words corresponding to the block
      * range. not all bits of the first and last words may be contained
      * within the block range.  if this is the case, we'll work against
      * those words (i.e. partial first and/or last) on an individual basis
      * (a single pass), allocating the bits of interest by hand and
      * updating the leaf corresponding to the dmap word. a single pass
      * will be used for all dmap words fully contained within the
      * specified range.  within this pass, the bits of all fully contained
      * dmap words will be marked as free in a single shot and the leaves
      * will be updated. a single leaf may describe the free space of
      * multiple dmap words, so we may update only a subset of the actual
      * leaves corresponding to the dmap words of the block range.
      */
     for (rembits = nblocks; rembits > 0; rembits -= nb, dbitno += nb) {
         /* determine the bit number within the word and
          * the number of bits within the word.
          */
         wbitno = dbitno & (DBWORD - 1);
         nb = min(rembits, DBWORD - wbitno);
 
         /* check if only part of a word is to be allocated.
          */
         if (nb < DBWORD) {
             /* allocate (set to 1) the appropriate bits within
              * this dmap word.
              */
             dp->wmap[word] |= cpu_to_le32(ONES << (DBWORD - nb)
                               >> wbitno);
 
             /* update the leaf for this dmap word. in addition
              * to setting the leaf value to the binary buddy max
              * of the updated dmap word, dbSplit() will split
              * the binary system of the leaves if need be.
              */
             dbSplit(tp, word, BUDMIN,
                 dbMaxBud((u8 *) & dp->wmap[word]));
 
             word += 1;
         } else {
             /* one or more dmap words are fully contained
              * within the block range.  determine how many
              * words and allocate (set to 1) the bits of these
              * words.
              */
             nwords = rembits >> L2DBWORD;
             memset(&dp->wmap[word], (int) ONES, nwords * 4);
 
             /* determine how many bits.
              */
             nb = nwords << L2DBWORD;
 
             /* now update the appropriate leaves to reflect
              * the allocated words.
              */
             for (; nwords > 0; nwords -= nw) {
                 if (leaf[word] < BUDMIN) {
                     jfs_error(bmp->db_ipbmap->i_sb,
                           "leaf page corrupt\n");
                     break;
                 }
 
                 /* determine what the leaf value should be
                  * updated to as the minimum of the l2 number
                  * of bits being allocated and the l2 number
                  * of bits currently described by this leaf.
                  */
                 size = min_t(int, leaf[word],
                          NLSTOL2BSZ(nwords));
 
                 /* update the leaf to reflect the allocation.
                  * in addition to setting the leaf value to
                  * NOFREE, dbSplit() will split the binary
                  * system of the leaves to reflect the current
                  * allocation (size).
                  */
                 dbSplit(tp, word, size, NOFREE);
 
                 /* get the number of dmap words handled */
                 nw = BUDSIZE(size, BUDMIN);
                 word += nw;
             }
         }
     }
 
     /* update the free count for this dmap */
     le32_add_cpu(&dp->nfree, -nblocks);
 
     BMAP_LOCK(bmp);
 
     /* if this allocation group is completely free,
      * update the maximum allocation group number if this allocation
      * group is the new max.
      */
     agno = blkno >> bmp->db_agl2size;
     if (agno > bmp->db_maxag)
         bmp->db_maxag = agno;
 
     /* update the free count for the allocation group and map */
     bmp->db_agfree[agno] -= nblocks;
     bmp->db_nfree -= nblocks;
 
     BMAP_UNLOCK(bmp);
 }
 
 
 /*
  * NAME:    dbFreeBits()
  *
  * FUNCTION:    free a specified block range from a dmap.
  *
  *      this routine updates the dmap to reflect the working
  *      state allocation of the specified block range. it directly
  *      updates the bits of the working map and causes the adjustment
  *      of the binary buddy system described by the dmap's dmtree
  *      leaves to reflect the bits freed.  it also causes the dmap's
  *      dmtree, as a whole, to reflect the deallocated range.
  *
  * PARAMETERS:
  *  bmp -  pointer to bmap descriptor
  *  dp  -  pointer to dmap to free bits from.
  *  blkno   -  starting block number of the bits to be freed.
  *  nblocks -  number of bits to be freed.
  *
  * RETURN VALUES: 0 for success
  *
  * serialization: IREAD_LOCK(ipbmap) or IWRITE_LOCK(ipbmap) held on entry/exit;
  */
 static int dbFreeBits(struct bmap * bmp, struct dmap * dp, s64 blkno,
                int nblocks)
 {
     int dbitno, word, rembits, nb, nwords, wbitno, nw, agno;
     dmtree_t *tp = (dmtree_t *) & dp->tree;
     int rc = 0;
     int size;
 
     /* determine the bit number and word within the dmap of the
      * starting block.
      */
     dbitno = blkno & (BPERDMAP - 1);
     word = dbitno >> L2DBWORD;
 
     /* block range better be within the dmap.
      */
     assert(dbitno + nblocks <= BPERDMAP);
 
     /* free the bits of the dmaps words corresponding to the block range.
      * not all bits of the first and last words may be contained within
      * the block range.  if this is the case, we'll work against those
      * words (i.e. partial first and/or last) on an individual basis
      * (a single pass), freeing the bits of interest by hand and updating
      * the leaf corresponding to the dmap word. a single pass will be used
      * for all dmap words fully contained within the specified range.
      * within this pass, the bits of all fully contained dmap words will
      * be marked as free in a single shot and the leaves will be updated. a
      * single leaf may describe the free space of multiple dmap words,
      * so we may update only a subset of the actual leaves corresponding
      * to the dmap words of the block range.
      *
      * dbJoin() is used to update leaf values and will join the binary
      * buddy system of the leaves if the new leaf values indicate this
      * should be done.
      */
     for (rembits = nblocks; rembits > 0; rembits -= nb, dbitno += nb) {
         /* determine the bit number within the word and
          * the number of bits within the word.
          */
         wbitno = dbitno & (DBWORD - 1);
         nb = min(rembits, DBWORD - wbitno);
 
         /* check if only part of a word is to be freed.
          */
         if (nb < DBWORD) {
             /* free (zero) the appropriate bits within this
              * dmap word.
              */
             dp->wmap[word] &=
                 cpu_to_le32(~(ONES << (DBWORD - nb)
                       >> wbitno));
 
             /* update the leaf for this dmap word.
              */
             rc = dbJoin(tp, word,
                     dbMaxBud((u8 *) & dp->wmap[word]));
             if (rc)
                 return rc;
 
             word += 1;
         } else {
             /* one or more dmap words are fully contained
              * within the block range.  determine how many
              * words and free (zero) the bits of these words.
              */
             nwords = rembits >> L2DBWORD;
             memset(&dp->wmap[word], 0, nwords * 4);
 
             /* determine how many bits.
              */
             nb = nwords << L2DBWORD;
 
             /* now update the appropriate leaves to reflect
              * the freed words.
              */
             for (; nwords > 0; nwords -= nw) {
                 /* determine what the leaf value should be
                  * updated to as the minimum of the l2 number
                  * of bits being freed and the l2 (max) number
                  * of bits that can be described by this leaf.
                  */
                 size =
                     min(LITOL2BSZ
                     (word, L2LPERDMAP, BUDMIN),
                     NLSTOL2BSZ(nwords));
 
                 /* update the leaf.
                  */
                 rc = dbJoin(tp, word, size);
                 if (rc)
                     return rc;
 
                 /* get the number of dmap words handled.
                  */
                 nw = BUDSIZE(size, BUDMIN);
                 word += nw;
             }
         }
     }
 
     /* update the free count for this dmap.
      */
     le32_add_cpu(&dp->nfree, nblocks);
 
     BMAP_LOCK(bmp);
 
     /* update the free count for the allocation group and
      * map.
      */
     agno = blkno >> bmp->db_agl2size;
     bmp->db_nfree += nblocks;
     bmp->db_agfree[agno] += nblocks;
 
     /* check if this allocation group is not completely free and
      * if it is currently the maximum (rightmost) allocation group.
      * if so, establish the new maximum allocation group number by
      * searching left for the first allocation group with allocation.
      */
     if ((bmp->db_agfree[agno] == bmp->db_agsize && agno == bmp->db_maxag) ||
         (agno == bmp->db_numag - 1 &&
          bmp->db_agfree[agno] == (bmp-> db_mapsize & (BPERDMAP - 1)))) {
         while (bmp->db_maxag > 0) {
             bmp->db_maxag -= 1;
             if (bmp->db_agfree[bmp->db_maxag] !=
                 bmp->db_agsize)
                 break;
         }
 
         /* re-establish the allocation group preference if the
          * current preference is right of the maximum allocation
          * group.
          */
         if (bmp->db_agpref > bmp->db_maxag)
             bmp->db_agpref = bmp->db_maxag;
     }
 
     BMAP_UNLOCK(bmp);
 
     return 0;
 }
 
 
 /*
  * NAME:    dbAdjCtl()
  *
  * FUNCTION:    adjust a dmap control page at a specified level to reflect
  *      the change in a lower level dmap or dmap control page's
  *      maximum string of free blocks (i.e. a change in the root
  *      of the lower level object's dmtree) due to the allocation
  *      or deallocation of a range of blocks with a single dmap.
  *
  *      on entry, this routine is provided with the new value of
  *      the lower level dmap or dmap control page root and the
  *      starting block number of the block range whose allocation
  *      or deallocation resulted in the root change.  this range
  *      is respresented by a single leaf of the current dmapctl
  *      and the leaf will be updated with this value, possibly
  *      causing a binary buddy system within the leaves to be
  *      split or joined.  the update may also cause the dmapctl's
  *      dmtree to be updated.
  *
  *      if the adjustment of the dmap control page, itself, causes its
  *      root to change, this change will be bubbled up to the next dmap
  *      control level by a recursive call to this routine, specifying
  *      the new root value and the next dmap control page level to
  *      be adjusted.
  * PARAMETERS:
  *  bmp -  pointer to bmap descriptor
  *  blkno   -  the first block of a block range within a dmap.  it is
  *         the allocation or deallocation of this block range that
  *         requires the dmap control page to be adjusted.
  *  newval  -  the new value of the lower level dmap or dmap control
  *         page root.
  *  alloc   -  'true' if adjustment is due to an allocation.
  *  level   -  current level of dmap control page (i.e. L0, L1, L2) to
  *         be adjusted.
  *
  * RETURN VALUES:
  *  0   - success
  *  -EIO    - i/o error
  *
  * serialization: IREAD_LOCK(ipbmap) or IWRITE_LOCK(ipbmap) held on entry/exit;
  */
 static int
 dbAdjCtl(struct bmap * bmp, s64 blkno, int newval, int alloc, int level)
 {
     struct metapage *mp;
     s8 oldroot;
     int oldval;
     s64 lblkno;
     struct dmapctl *dcp;
     int rc, leafno, ti;
 
     /* get the buffer for the dmap control page for the specified
      * block number and control page level.
      */
     lblkno = BLKTOCTL(blkno, bmp->db_l2nbperpage, level);
     mp = read_metapage(bmp->db_ipbmap, lblkno, PSIZE, 0);
     if (mp == NULL)
         return -EIO;
     dcp = (struct dmapctl *) mp->data;
 
     if (dcp->leafidx != cpu_to_le32(CTLLEAFIND)) {
         jfs_error(bmp->db_ipbmap->i_sb, "Corrupt dmapctl page\n");
         release_metapage(mp);
         return -EIO;
     }
 
     /* determine the leaf number corresponding to the block and
      * the index within the dmap control tree.
      */
     leafno = BLKTOCTLLEAF(blkno, dcp->budmin);
     ti = leafno + le32_to_cpu(dcp->leafidx);
 
     /* save the current leaf value and the current root level (i.e.
      * maximum l2 free string described by this dmapctl).
      */
     oldval = dcp->stree[ti];
     oldroot = dcp->stree[ROOT];
 
     /* check if this is a control page update for an allocation.
      * if so, update the leaf to reflect the new leaf value using
      * dbSplit(); otherwise (deallocation), use dbJoin() to update
      * the leaf with the new value.  in addition to updating the
      * leaf, dbSplit() will also split the binary buddy system of
      * the leaves, if required, and bubble new values within the
      * dmapctl tree, if required.  similarly, dbJoin() will join
      * the binary buddy system of leaves and bubble new values up
      * the dmapctl tree as required by the new leaf value.
      */
     if (alloc) {
         /* check if we are in the middle of a binary buddy
          * system.  this happens when we are performing the
          * first allocation out of an allocation group that
          * is part (not the first part) of a larger binary
          * buddy system.  if we are in the middle, back split
          * the system prior to calling dbSplit() which assumes
          * that it is at the front of a binary buddy system.
          */
         if (oldval == NOFREE) {
             rc = dbBackSplit((dmtree_t *) dcp, leafno);
             if (rc) {
                 release_metapage(mp);
                 return rc;
             }
             oldval = dcp->stree[ti];
         }
         dbSplit((dmtree_t *) dcp, leafno, dcp->budmin, newval);
     } else {
         rc = dbJoin((dmtree_t *) dcp, leafno, newval);
         if (rc) {
             release_metapage(mp);
             return rc;
         }
     }
 
     /* check if the root of the current dmap control page changed due
      * to the update and if the current dmap control page is not at
      * the current top level (i.e. L0, L1, L2) of the map.  if so (i.e.
      * root changed and this is not the top level), call this routine
      * again (recursion) for the next higher level of the mapping to
      * reflect the change in root for the current dmap control page.
      */
     if (dcp->stree[ROOT] != oldroot) {
         /* are we below the top level of the map.  if so,
          * bubble the root up to the next higher level.
          */
         if (level < bmp->db_maxlevel) {
             /* bubble up the new root of this dmap control page to
              * the next level.
              */
             if ((rc =
                  dbAdjCtl(bmp, blkno, dcp->stree[ROOT], alloc,
                       level + 1))) {
                 /* something went wrong in bubbling up the new
                  * root value, so backout the changes to the
                  * current dmap control page.
                  */
                 if (alloc) {
                     dbJoin((dmtree_t *) dcp, leafno,
                            oldval);
                 } else {
                     /* the dbJoin() above might have
                      * caused a larger binary buddy system
                      * to form and we may now be in the
                      * middle of it.  if this is the case,
                      * back split the buddies.
                      */
                     if (dcp->stree[ti] == NOFREE)
                         dbBackSplit((dmtree_t *)
                                 dcp, leafno);
                     dbSplit((dmtree_t *) dcp, leafno,
                         dcp->budmin, oldval);
                 }
 
                 /* release the buffer and return the error.
                  */
                 release_metapage(mp);
                 return (rc);
             }
         } else {
             /* we're at the top level of the map. update
              * the bmap control page to reflect the size
              * of the maximum free buddy system.
              */
             assert(level == bmp->db_maxlevel);
             if (bmp->db_maxfreebud != oldroot) {
                 jfs_error(bmp->db_ipbmap->i_sb,
                       "the maximum free buddy is not the old root\n");
             }
             bmp->db_maxfreebud = dcp->stree[ROOT];
         }
     }
 
     /* write the buffer.
      */
     write_metapage(mp);
 
     return (0);
 }
 
 
 /*
  * NAME:    dbSplit()
  *
  * FUNCTION:    update the leaf of a dmtree with a new value, splitting
  *      the leaf from the binary buddy system of the dmtree's
  *      leaves, as required.
  *
  * PARAMETERS:
  *  tp  - pointer to the tree containing the leaf.
  *  leafno  - the number of the leaf to be updated.
  *  splitsz - the size the binary buddy system starting at the leaf
  *        must be split to, specified as the log2 number of blocks.
  *  newval  - the new value for the leaf.
  *
  * RETURN VALUES: none
  *
  * serialization: IREAD_LOCK(ipbmap) or IWRITE_LOCK(ipbmap) held on entry/exit;
  */
 static void dbSplit(dmtree_t * tp, int leafno, int splitsz, int newval)
 {
     int budsz;
     int cursz;
     s8 *leaf = tp->dmt_stree + le32_to_cpu(tp->dmt_leafidx);
 
     /* check if the leaf needs to be split.
      */
     if (leaf[leafno] > tp->dmt_budmin) {
         /* the split occurs by cutting the buddy system in half
          * at the specified leaf until we reach the specified
          * size.  pick up the starting split size (current size
          * - 1 in l2) and the corresponding buddy size.
          */
         cursz = leaf[leafno] - 1;
         budsz = BUDSIZE(cursz, tp->dmt_budmin);
 
         /* split until we reach the specified size.
          */
         while (cursz >= splitsz) {
             /* update the buddy's leaf with its new value.
              */
             dbAdjTree(tp, leafno ^ budsz, cursz);
 
             /* on to the next size and buddy.
              */
             cursz -= 1;
             budsz >>= 1;
         }
     }
 
     /* adjust the dmap tree to reflect the specified leaf's new
      * value.
      */
     dbAdjTree(tp, leafno, newval);
 }
 
 
 /*
  * NAME:    dbBackSplit()
  *
  * FUNCTION:    back split the binary buddy system of dmtree leaves
  *      that hold a specified leaf until the specified leaf
  *      starts its own binary buddy system.
  *
  *      the allocators typically perform allocations at the start
  *      of binary buddy systems and dbSplit() is used to accomplish
  *      any required splits.  in some cases, however, allocation
  *      may occur in the middle of a binary system and requires a
  *      back split, with the split proceeding out from the middle of
  *      the system (less efficient) rather than the start of the
  *      system (more efficient).  the cases in which a back split
  *      is required are rare and are limited to the first allocation
  *      within an allocation group which is a part (not first part)
  *      of a larger binary buddy system and a few exception cases
  *      in which a previous join operation must be backed out.
  *
  * PARAMETERS:
  *  tp  - pointer to the tree containing the leaf.
  *  leafno  - the number of the leaf to be updated.
  *
  * RETURN VALUES: none
  *
  * serialization: IREAD_LOCK(ipbmap) or IWRITE_LOCK(ipbmap) held on entry/exit;
  */
 static int dbBackSplit(dmtree_t * tp, int leafno)
 {
     int budsz, bud, w, bsz, size;
     int cursz;
     s8 *leaf = tp->dmt_stree + le32_to_cpu(tp->dmt_leafidx);
 
     /* leaf should be part (not first part) of a binary
      * buddy system.
      */
     assert(leaf[leafno] == NOFREE);
 
     /* the back split is accomplished by iteratively finding the leaf
      * that starts the buddy system that contains the specified leaf and
      * splitting that system in two.  this iteration continues until
      * the specified leaf becomes the start of a buddy system.
      *
      * determine maximum possible l2 size for the specified leaf.
      */
     size =
         LITOL2BSZ(leafno, le32_to_cpu(tp->dmt_l2nleafs),
               tp->dmt_budmin);
 
     /* determine the number of leaves covered by this size.  this
      * is the buddy size that we will start with as we search for
      * the buddy system that contains the specified leaf.
      */
     budsz = BUDSIZE(size, tp->dmt_budmin);
 
     /* back split.
      */
     while (leaf[leafno] == NOFREE) {
         /* find the leftmost buddy leaf.
          */
         for (w = leafno, bsz = budsz;; bsz <<= 1,
              w = (w < bud) ? w : bud) {
             if (bsz >= le32_to_cpu(tp->dmt_nleafs)) {
                 jfs_err("JFS: block map error in dbBackSplit");
                 return -EIO;
             }
 
             /* determine the buddy.
              */
             bud = w ^ bsz;
 
             /* check if this buddy is the start of the system.
              */
             if (leaf[bud] != NOFREE) {
                 /* split the leaf at the start of the
                  * system in two.
                  */
                 cursz = leaf[bud] - 1;
                 dbSplit(tp, bud, cursz, cursz);
                 break;
             }
         }
     }
 
     if (leaf[leafno] != size) {
         jfs_err("JFS: wrong leaf value in dbBackSplit");
         return -EIO;
     }
     return 0;
 }
 
 
 /*
  * NAME:    dbJoin()
  *
  * FUNCTION:    update the leaf of a dmtree with a new value, joining
  *      the leaf with other leaves of the dmtree into a multi-leaf
  *      binary buddy system, as required.
  *
  * PARAMETERS:
  *  tp  - pointer to the tree containing the leaf.
  *  leafno  - the number of the leaf to be updated.
  *  newval  - the new value for the leaf.
  *
  * RETURN VALUES: none
  */
 static int dbJoin(dmtree_t * tp, int leafno, int newval)
 {
     int budsz, buddy;
     s8 *leaf;
 
     /* can the new leaf value require a join with other leaves ?
      */
     if (newval >= tp->dmt_budmin) {
         /* pickup a pointer to the leaves of the tree.
          */
         leaf = tp->dmt_stree + le32_to_cpu(tp->dmt_leafidx);
 
         /* try to join the specified leaf into a large binary
          * buddy system.  the join proceeds by attempting to join
          * the specified leafno with its buddy (leaf) at new value.
          * if the join occurs, we attempt to join the left leaf
          * of the joined buddies with its buddy at new value + 1.
          * we continue to join until we find a buddy that cannot be
          * joined (does not have a value equal to the size of the
          * last join) or until all leaves have been joined into a
          * single system.
          *
          * get the buddy size (number of words covered) of
          * the new value.
          */
         budsz = BUDSIZE(newval, tp->dmt_budmin);
 
         /* try to join.
          */
         while (budsz < le32_to_cpu(tp->dmt_nleafs)) {
             /* get the buddy leaf.
              */
             buddy = leafno ^ budsz;
 
             /* if the leaf's new value is greater than its
              * buddy's value, we join no more.
              */
             if (newval > leaf[buddy])
                 break;
 
             /* It shouldn't be less */
             if (newval < leaf[buddy])
                 return -EIO;
 
             /* check which (leafno or buddy) is the left buddy.
              * the left buddy gets to claim the blocks resulting
              * from the join while the right gets to claim none.
              * the left buddy is also eligible to participate in
              * a join at the next higher level while the right
              * is not.
              *
              */
             if (leafno < buddy) {
                 /* leafno is the left buddy.
                  */
                 dbAdjTree(tp, buddy, NOFREE);
             } else {
                 /* buddy is the left buddy and becomes
                  * leafno.
                  */
                 dbAdjTree(tp, leafno, NOFREE);
                 leafno = buddy;
             }
 
             /* on to try the next join.
              */
             newval += 1;
             budsz <<= 1;
         }
     }
 
     /* update the leaf value.
      */
     dbAdjTree(tp, leafno, newval);
 
     return 0;
 }
 
 
 /*
  * NAME:    dbAdjTree()
  *
  * FUNCTION:    update a leaf of a dmtree with a new value, adjusting
  *      the dmtree, as required, to reflect the new leaf value.
  *      the combination of any buddies must already be done before
  *      this is called.
  *
  * PARAMETERS:
  *  tp  - pointer to the tree to be adjusted.
  *  leafno  - the number of the leaf to be updated.
  *  newval  - the new value for the leaf.
  *
  * RETURN VALUES: none
  */
 static void dbAdjTree(dmtree_t * tp, int leafno, int newval)
 {
     int lp, pp, k;
     int max;
 
     /* pick up the index of the leaf for this leafno.
      */
     lp = leafno + le32_to_cpu(tp->dmt_leafidx);
 
     /* is the current value the same as the old value ?  if so,
      * there is nothing to do.
      */
     if (tp->dmt_stree[lp] == newval)
         return;
 
     /* set the new value.
      */
     tp->dmt_stree[lp] = newval;
 
     /* bubble the new value up the tree as required.
      */
     for (k = 0; k < le32_to_cpu(tp->dmt_height); k++) {
         /* get the index of the first leaf of the 4 leaf
          * group containing the specified leaf (leafno).
          */
         lp = ((lp - 1) & ~0x03) + 1;
 
         /* get the index of the parent of this 4 leaf group.
          */
         pp = (lp - 1) >> 2;
 
         /* determine the maximum of the 4 leaves.
          */
         max = TREEMAX(&tp->dmt_stree[lp]);
 
         /* if the maximum of the 4 is the same as the
          * parent's value, we're done.
          */
         if (tp->dmt_stree[pp] == max)
             break;
 
         /* parent gets new value.
          */
         tp->dmt_stree[pp] = max;
 
         /* parent becomes leaf for next go-round.
          */
         lp = pp;
     }
 }
 
 
 /*
  * NAME:    dbFindLeaf()
  *
  * FUNCTION:    search a dmtree_t for sufficient free blocks, returning
  *      the index of a leaf describing the free blocks if
  *      sufficient free blocks are found.
  *
  *      the search starts at the top of the dmtree_t tree and
  *      proceeds down the tree to the leftmost leaf with sufficient
  *      free space.
  *
  * PARAMETERS:
  *  tp  - pointer to the tree to be searched.
  *  l2nb    - log2 number of free blocks to search for.
  *  leafidx - return pointer to be set to the index of the leaf
  *        describing at least l2nb free blocks if sufficient
  *        free blocks are found.
  *
  * RETURN VALUES:
  *  0   - success
  *  -ENOSPC - insufficient free blocks.
  */
 static int dbFindLeaf(dmtree_t * tp, int l2nb, int *leafidx)
 {
     int ti, n = 0, k, x = 0;
 
     /* first check the root of the tree to see if there is
      * sufficient free space.
      */
     if (l2nb > tp->dmt_stree[ROOT])
         return -ENOSPC;
 
     /* sufficient free space available. now search down the tree
      * starting at the next level for the leftmost leaf that
      * describes sufficient free space.
      */
     for (k = le32_to_cpu(tp->dmt_height), ti = 1;
          k > 0; k--, ti = ((ti + n) << 2) + 1) {
         /* search the four nodes at this level, starting from
          * the left.
          */
         for (x = ti, n = 0; n < 4; n++) {
             /* sufficient free space found.  move to the next
              * level (or quit if this is the last level).
              */
             if (l2nb <= tp->dmt_stree[x + n])
                 break;
         }
 
         /* better have found something since the higher
          * levels of the tree said it was here.
          */
         assert(n < 4);
     }
 
     /* set the return to the leftmost leaf describing sufficient
      * free space.
      */
     *leafidx = x + n - le32_to_cpu(tp->dmt_leafidx);
 
     return (0);
 }
 
 
 /*
  * NAME:    dbFindBits()
  *
  * FUNCTION:    find a specified number of binary buddy free bits within a
  *      dmap bitmap word value.
  *
  *      this routine searches the bitmap value for (1 << l2nb) free
  *      bits at (1 << l2nb) alignments within the value.
  *
  * PARAMETERS:
  *  word    -  dmap bitmap word value.
  *  l2nb    -  number of free bits specified as a log2 number.
  *
  * RETURN VALUES:
  *  starting bit number of free bits.
  */
 static int dbFindBits(u32 word, int l2nb)
 {
     int bitno, nb;
     u32 mask;
 
     /* get the number of bits.
      */
     nb = 1 << l2nb;
     assert(nb <= DBWORD);
 
     /* complement the word so we can use a mask (i.e. 0s represent
      * free bits) and compute the mask.
      */
     word = ~word;
     mask = ONES << (DBWORD - nb);
 
     /* scan the word for nb free bits at nb alignments.
      */
     for (bitno = 0; mask != 0; bitno += nb, mask >>= nb) {
         if ((mask & word) == mask)
             break;
     }
 
     ASSERT(bitno < 32);
 
     /* return the bit number.
      */
     return (bitno);
 }
 
 
 /*
  * NAME:    dbMaxBud(u8 *cp)
  *
  * FUNCTION:    determine the largest binary buddy string of free
  *      bits within 32-bits of the map.
  *
  * PARAMETERS:
  *  cp  -  pointer to the 32-bit value.
  *
  * RETURN VALUES:
  *  largest binary buddy of free bits within a dmap word.
  */
 static int dbMaxBud(u8 * cp)
 {
     signed char tmp1, tmp2;
 
     /* check if the wmap word is all free. if so, the
      * free buddy size is BUDMIN.
      */
     if (*((uint *) cp) == 0)
         return (BUDMIN);
 
     /* check if the wmap word is half free. if so, the
      * free buddy size is BUDMIN-1.
      */
     if (*((u16 *) cp) == 0 || *((u16 *) cp + 1) == 0)
         return (BUDMIN - 1);
 
     /* not all free or half free. determine the free buddy
      * size thru table lookup using quarters of the wmap word.
      */
     tmp1 = max(budtab[cp[2]], budtab[cp[3]]);
     tmp2 = max(budtab[cp[0]], budtab[cp[1]]);
     return (max(tmp1, tmp2));
 }
 
 
 /*
  * NAME:    cnttz(uint word)
  *
  * FUNCTION:    determine the number of trailing zeros within a 32-bit
  *      value.
  *
  * PARAMETERS:
  *  value   -  32-bit value to be examined.
  *
  * RETURN VALUES:
  *  count of trailing zeros
  */
 static int cnttz(u32 word)
 {
     int n;
 
     for (n = 0; n < 32; n++, word >>= 1) {
         if (word & 0x01)
             break;
     }
 
     return (n);
 }
 
 
 /*
  * NAME:    cntlz(u32 value)
  *
  * FUNCTION:    determine the number of leading zeros within a 32-bit
  *      value.
  *
  * PARAMETERS:
  *  value   -  32-bit value to be examined.
  *
  * RETURN VALUES:
  *  count of leading zeros
  */
 static int cntlz(u32 value)
 {
     int n;
 
     for (n = 0; n < 32; n++, value <<= 1) {
         if (value & HIGHORDER)
             break;
     }
     return (n);
 }
 
 
 /*
  * NAME:    blkstol2(s64 nb)
  *
  * FUNCTION:    convert a block count to its log2 value. if the block
  *      count is not a l2 multiple, it is rounded up to the next
  *      larger l2 multiple.
  *
  * PARAMETERS:
  *  nb  -  number of blocks
  *
  * RETURN VALUES:
  *  log2 number of blocks
  */
 static int blkstol2(s64 nb)
 {
     int l2nb;
     s64 mask;       /* meant to be signed */
 
     mask = (s64) 1 << (64 - 1);
 
     /* count the leading bits.
      */
     for (l2nb = 0; l2nb < 64; l2nb++, mask >>= 1) {
         /* leading bit found.
          */
         if (nb & mask) {
             /* determine the l2 value.
              */
             l2nb = (64 - 1) - l2nb;
 
             /* check if we need to round up.
              */
             if (~mask & nb)
                 l2nb++;
 
             return (l2nb);
         }
     }
     assert(0);
     return 0;       /* fix compiler warning */
 }
 
 
 /*
  * NAME:    dbAllocBottomUp()
  *
  * FUNCTION:    alloc the specified block range from the working block
  *      allocation map.
  *
  *      the blocks will be alloc from the working map one dmap
  *      at a time.
  *
  * PARAMETERS:
  *  ip  -  pointer to in-core inode;
  *  blkno   -  starting block number to be freed.
  *  nblocks -  number of blocks to be freed.
  *
  * RETURN VALUES:
  *  0   - success
  *  -EIO    - i/o error
  */
 int dbAllocBottomUp(struct inode *ip, s64 blkno, s64 nblocks)
 {
     struct metapage *mp;
     struct dmap *dp;
     int nb, rc;
     s64 lblkno, rem;
     struct inode *ipbmap = JFS_SBI(ip->i_sb)->ipbmap;
     struct bmap *bmp = JFS_SBI(ip->i_sb)->bmap;
 
     IREAD_LOCK(ipbmap, RDWRLOCK_DMAP);
 
     /* block to be allocated better be within the mapsize. */
     ASSERT(nblocks <= bmp->db_mapsize - blkno);
 
     /*
      * allocate the blocks a dmap at a time.
      */
     mp = NULL;
     for (rem = nblocks; rem > 0; rem -= nb, blkno += nb) {
         /* release previous dmap if any */
         if (mp) {
             write_metapage(mp);
         }
 
         /* get the buffer for the current dmap. */
         lblkno = BLKTODMAP(blkno, bmp->db_l2nbperpage);
         mp = read_metapage(ipbmap, lblkno, PSIZE, 0);
         if (mp == NULL) {
             IREAD_UNLOCK(ipbmap);
             return -EIO;
         }
         dp = (struct dmap *) mp->data;
 
         /* determine the number of blocks to be allocated from
          * this dmap.
          */
         nb = min(rem, BPERDMAP - (blkno & (BPERDMAP - 1)));
 
         /* allocate the blocks. */
         if ((rc = dbAllocDmapBU(bmp, dp, blkno, nb))) {
             release_metapage(mp);
             IREAD_UNLOCK(ipbmap);
             return (rc);
         }
     }
 
     /* write the last buffer. */
     write_metapage(mp);
 
     IREAD_UNLOCK(ipbmap);
 
     return (0);
 }
 
 
 static int dbAllocDmapBU(struct bmap * bmp, struct dmap * dp, s64 blkno,
              int nblocks)
 {
     int rc;
     int dbitno, word, rembits, nb, nwords, wbitno, agno;
     s8 oldroot;
     struct dmaptree *tp = (struct dmaptree *) & dp->tree;
 
     /* save the current value of the root (i.e. maximum free string)
      * of the dmap tree.
      */
     oldroot = tp->stree[ROOT];
 
     /* determine the bit number and word within the dmap of the
      * starting block.
      */
     dbitno = blkno & (BPERDMAP - 1);
     word = dbitno >> L2DBWORD;
 
     /* block range better be within the dmap */
     assert(dbitno + nblocks <= BPERDMAP);
 
     /* allocate the bits of the dmap's words corresponding to the block
      * range. not all bits of the first and last words may be contained
      * within the block range.  if this is the case, we'll work against
      * those words (i.e. partial first and/or last) on an individual basis
      * (a single pass), allocating the bits of interest by hand and
      * updating the leaf corresponding to the dmap word. a single pass
      * will be used for all dmap words fully contained within the
      * specified range.  within this pass, the bits of all fully contained
      * dmap words will be marked as free in a single shot and the leaves
      * will be updated. a single leaf may describe the free space of
      * multiple dmap words, so we may update only a subset of the actual
      * leaves corresponding to the dmap words of the block range.
      */
     for (rembits = nblocks; rembits > 0; rembits -= nb, dbitno += nb) {
         /* determine the bit number within the word and
          * the number of bits within the word.
          */
         wbitno = dbitno & (DBWORD - 1);
         nb = min(rembits, DBWORD - wbitno);
 
         /* check if only part of a word is to be allocated.
          */
         if (nb < DBWORD) {
             /* allocate (set to 1) the appropriate bits within
              * this dmap word.
              */
             dp->wmap[word] |= cpu_to_le32(ONES << (DBWORD - nb)
                               >> wbitno);
 
             word++;
         } else {
             /* one or more dmap words are fully contained
              * within the block range.  determine how many
              * words and allocate (set to 1) the bits of these
              * words.
              */
             nwords = rembits >> L2DBWORD;
             memset(&dp->wmap[word], (int) ONES, nwords * 4);
 
             /* determine how many bits */
             nb = nwords << L2DBWORD;
             word += nwords;
         }
     }
 
     /* update the free count for this dmap */
     le32_add_cpu(&dp->nfree, -nblocks);
 
     /* reconstruct summary tree */
     dbInitDmapTree(dp);
 
     BMAP_LOCK(bmp);
 
     /* if this allocation group is completely free,
      * update the highest active allocation group number
      * if this allocation group is the new max.
      */
     agno = blkno >> bmp->db_agl2size;
     if (agno > bmp->db_maxag)
         bmp->db_maxag = agno;
 
     /* update the free count for the allocation group and map */
     bmp->db_agfree[agno] -= nblocks;
     bmp->db_nfree -= nblocks;
 
     BMAP_UNLOCK(bmp);
 
     /* if the root has not changed, done. */
     if (tp->stree[ROOT] == oldroot)
         return (0);
 
     /* root changed. bubble the change up to the dmap control pages.
      * if the adjustment of the upper level control pages fails,
      * backout the bit allocation (thus making everything consistent).
      */
     if ((rc = dbAdjCtl(bmp, blkno, tp->stree[ROOT], 1, 0)))
         dbFreeBits(bmp, dp, blkno, nblocks);
 
     return (rc);
 }
 
 
 /*
  * NAME:    dbExtendFS()
  *
  * FUNCTION:    extend bmap from blkno for nblocks;
  *      dbExtendFS() updates bmap ready for dbAllocBottomUp();
  *
  * L2
  *  |
  *   L1---------------------------------L1
  *    |                  |
  *     L0---------L0---------L0       L0---------L0---------L0
  *      |      |          |        |          |      |
  *   d0,...,dn  d0,...,dn  d0,...,dn    d0,...,dn  d0,...,dn  d0,.,dm;
  * L2L1L0d0,...,dnL0d0,...,dnL0d0,...,dnL1L0d0,...,dnL0d0,...,dnL0d0,..dm
  *
  * <---old---><----------------------------extend----------------------->
  */
 int dbExtendFS(struct inode *ipbmap, s64 blkno, s64 nblocks)
 {
     struct jfs_sb_info *sbi = JFS_SBI(ipbmap->i_sb);
     int nbperpage = sbi->nbperpage;
     int i, i0 = true, j, j0 = true, k, n;
     s64 newsize;
     s64 p;
     struct metapage *mp, *l2mp, *l1mp = NULL, *l0mp = NULL;
     struct dmapctl *l2dcp, *l1dcp, *l0dcp;
     struct dmap *dp;
     s8 *l0leaf, *l1leaf, *l2leaf;
     struct bmap *bmp = sbi->bmap;
     int agno, l2agsize, oldl2agsize;
     s64 ag_rem;
 
     newsize = blkno + nblocks;
 
     jfs_info("dbExtendFS: blkno:%Ld nblocks:%Ld newsize:%Ld",
          (long long) blkno, (long long) nblocks, (long long) newsize);
 
     /*
      *  initialize bmap control page.
      *
      * all the data in bmap control page should exclude
      * the mkfs hidden dmap page.
      */
 
     /* update mapsize */
     bmp->db_mapsize = newsize;
     bmp->db_maxlevel = BMAPSZTOLEV(bmp->db_mapsize);
 
     /* compute new AG size */
     l2agsize = dbGetL2AGSize(newsize);
     oldl2agsize = bmp->db_agl2size;
 
     bmp->db_agl2size = l2agsize;
     bmp->db_agsize = 1 << l2agsize;
 
     /* compute new number of AG */
     agno = bmp->db_numag;
     bmp->db_numag = newsize >> l2agsize;
     bmp->db_numag += ((u32) newsize % (u32) bmp->db_agsize) ? 1 : 0;
 
     /*
      *  reconfigure db_agfree[]
      * from old AG configuration to new AG configuration;
      *
      * coalesce contiguous k (newAGSize/oldAGSize) AGs;
      * i.e., (AGi, ..., AGj) where i = k*n and j = k*(n+1) - 1 to AGn;
      * note: new AG size = old AG size * (2**x).
      */
     if (l2agsize == oldl2agsize)
         goto extend;
     k = 1 << (l2agsize - oldl2agsize);
     ag_rem = bmp->db_agfree[0]; /* save agfree[0] */
     for (i = 0, n = 0; i < agno; n++) {
         bmp->db_agfree[n] = 0;  /* init collection point */
 
         /* coalesce contiguous k AGs; */
         for (j = 0; j < k && i < agno; j++, i++) {
             /* merge AGi to AGn */
             bmp->db_agfree[n] += bmp->db_agfree[i];
         }
     }
     bmp->db_agfree[0] += ag_rem;    /* restore agfree[0] */
 
     for (; n < MAXAG; n++)
         bmp->db_agfree[n] = 0;
 
     /*
      * update highest active ag number
      */
 
     bmp->db_maxag = bmp->db_maxag / k;
 
     /*
      *  extend bmap
      *
      * update bit maps and corresponding level control pages;
      * global control page db_nfree, db_agfree[agno], db_maxfreebud;
      */
       extend:
     /* get L2 page */
     p = BMAPBLKNO + nbperpage;  /* L2 page */
     l2mp = read_metapage(ipbmap, p, PSIZE, 0);
     if (!l2mp) {
         jfs_error(ipbmap->i_sb, "L2 page could not be read\n");
         return -EIO;
     }
     l2dcp = (struct dmapctl *) l2mp->data;
 
     /* compute start L1 */
     k = blkno >> L2MAXL1SIZE;
     l2leaf = l2dcp->stree + CTLLEAFIND + k;
     p = BLKTOL1(blkno, sbi->l2nbperpage);   /* L1 page */
 
     /*
      * extend each L1 in L2
      */
     for (; k < LPERCTL; k++, p += nbperpage) {
         /* get L1 page */
         if (j0) {
             /* read in L1 page: (blkno & (MAXL1SIZE - 1)) */
             l1mp = read_metapage(ipbmap, p, PSIZE, 0);
             if (l1mp == NULL)
                 goto errout;
             l1dcp = (struct dmapctl *) l1mp->data;
 
             /* compute start L0 */
             j = (blkno & (MAXL1SIZE - 1)) >> L2MAXL0SIZE;
             l1leaf = l1dcp->stree + CTLLEAFIND + j;
             p = BLKTOL0(blkno, sbi->l2nbperpage);
             j0 = false;
         } else {
             /* assign/init L1 page */
             l1mp = get_metapage(ipbmap, p, PSIZE, 0);
             if (l1mp == NULL)
                 goto errout;
 
             l1dcp = (struct dmapctl *) l1mp->data;
 
             /* compute start L0 */
             j = 0;
             l1leaf = l1dcp->stree + CTLLEAFIND;
             p += nbperpage; /* 1st L0 of L1.k */
         }
 
         /*
          * extend each L0 in L1
          */
         for (; j < LPERCTL; j++) {
             /* get L0 page */
             if (i0) {
                 /* read in L0 page: (blkno & (MAXL0SIZE - 1)) */
 
                 l0mp = read_metapage(ipbmap, p, PSIZE, 0);
                 if (l0mp == NULL)
                     goto errout;
                 l0dcp = (struct dmapctl *) l0mp->data;
 
                 /* compute start dmap */
                 i = (blkno & (MAXL0SIZE - 1)) >>
                     L2BPERDMAP;
                 l0leaf = l0dcp->stree + CTLLEAFIND + i;
                 p = BLKTODMAP(blkno,
                           sbi->l2nbperpage);
                 i0 = false;
             } else {
                 /* assign/init L0 page */
                 l0mp = get_metapage(ipbmap, p, PSIZE, 0);
                 if (l0mp == NULL)
                     goto errout;
 
                 l0dcp = (struct dmapctl *) l0mp->data;
 
                 /* compute start dmap */
                 i = 0;
                 l0leaf = l0dcp->stree + CTLLEAFIND;
                 p += nbperpage; /* 1st dmap of L0.j */
             }
 
             /*
              * extend each dmap in L0
              */
             for (; i < LPERCTL; i++) {
                 /*
                  * reconstruct the dmap page, and
                  * initialize corresponding parent L0 leaf
                  */
                 if ((n = blkno & (BPERDMAP - 1))) {
                     /* read in dmap page: */
                     mp = read_metapage(ipbmap, p,
                                PSIZE, 0);
                     if (mp == NULL)
                         goto errout;
                     n = min(nblocks, (s64)BPERDMAP - n);
                 } else {
                     /* assign/init dmap page */
                     mp = read_metapage(ipbmap, p,
                                PSIZE, 0);
                     if (mp == NULL)
                         goto errout;
 
                     n = min_t(s64, nblocks, BPERDMAP);
                 }
 
                 dp = (struct dmap *) mp->data;
                 *l0leaf = dbInitDmap(dp, blkno, n);
 
                 bmp->db_nfree += n;
                 agno = le64_to_cpu(dp->start) >> l2agsize;
                 bmp->db_agfree[agno] += n;
 
                 write_metapage(mp);
 
                 l0leaf++;
                 p += nbperpage;
 
                 blkno += n;
                 nblocks -= n;
                 if (nblocks == 0)
                     break;
             }   /* for each dmap in a L0 */
 
             /*
              * build current L0 page from its leaves, and
              * initialize corresponding parent L1 leaf
              */
             *l1leaf = dbInitDmapCtl(l0dcp, 0, ++i);
             write_metapage(l0mp);
             l0mp = NULL;
 
             if (nblocks)
                 l1leaf++;   /* continue for next L0 */
             else {
                 /* more than 1 L0 ? */
                 if (j > 0)
                     break;  /* build L1 page */
                 else {
                     /* summarize in global bmap page */
                     bmp->db_maxfreebud = *l1leaf;
                     release_metapage(l1mp);
                     release_metapage(l2mp);
                     goto finalize;
                 }
             }
         }       /* for each L0 in a L1 */
 
         /*
          * build current L1 page from its leaves, and
          * initialize corresponding parent L2 leaf
          */
         *l2leaf = dbInitDmapCtl(l1dcp, 1, ++j);
         write_metapage(l1mp);
         l1mp = NULL;
 
         if (nblocks)
             l2leaf++;   /* continue for next L1 */
         else {
             /* more than 1 L1 ? */
             if (k > 0)
                 break;  /* build L2 page */
             else {
                 /* summarize in global bmap page */
                 bmp->db_maxfreebud = *l2leaf;
                 release_metapage(l2mp);
                 goto finalize;
             }
         }
     }           /* for each L1 in a L2 */
 
     jfs_error(ipbmap->i_sb, "function has not returned as expected\n");
 errout:
     if (l0mp)
         release_metapage(l0mp);
     if (l1mp)
         release_metapage(l1mp);
     release_metapage(l2mp);
     return -EIO;
 
     /*
      *  finalize bmap control page
      */
 finalize:
 
     return 0;
 }
 
 
 /*
  *  dbFinalizeBmap()
  */
 void dbFinalizeBmap(struct inode *ipbmap)
 {
     struct bmap *bmp = JFS_SBI(ipbmap->i_sb)->bmap;
     int actags, inactags, l2nl;
     s64 ag_rem, actfree, inactfree, avgfree;
     int i, n;
 
     /*
      *  finalize bmap control page
      */
 //finalize:
     /*
      * compute db_agpref: preferred ag to allocate from
      * (the leftmost ag with average free space in it);
      */
 //agpref:
     /* get the number of active ags and inactive ags */
     actags = bmp->db_maxag + 1;
     inactags = bmp->db_numag - actags;
     ag_rem = bmp->db_mapsize & (bmp->db_agsize - 1);    /* ??? */
 
     /* determine how many blocks are in the inactive allocation
      * groups. in doing this, we must account for the fact that
      * the rightmost group might be a partial group (i.e. file
      * system size is not a multiple of the group size).
      */
     inactfree = (inactags && ag_rem) ?
         ((inactags - 1) << bmp->db_agl2size) + ag_rem
         : inactags << bmp->db_agl2size;
 
     /* determine how many free blocks are in the active
      * allocation groups plus the average number of free blocks
      * within the active ags.
      */
     actfree = bmp->db_nfree - inactfree;
     avgfree = (u32) actfree / (u32) actags;
 
     /* if the preferred allocation group has not average free space.
      * re-establish the preferred group as the leftmost
      * group with average free space.
      */
     if (bmp->db_agfree[bmp->db_agpref] < avgfree) {
         for (bmp->db_agpref = 0; bmp->db_agpref < actags;
              bmp->db_agpref++) {
             if (bmp->db_agfree[bmp->db_agpref] >= avgfree)
                 break;
         }
         if (bmp->db_agpref >= bmp->db_numag) {
             jfs_error(ipbmap->i_sb,
                   "cannot find ag with average freespace\n");
         }
     }
 
     /*
      * compute db_aglevel, db_agheight, db_width, db_agstart:
      * an ag is covered in aglevel dmapctl summary tree,
      * at agheight level height (from leaf) with agwidth number of nodes
      * each, which starts at agstart index node of the smmary tree node
      * array;
      */
     bmp->db_aglevel = BMAPSZTOLEV(bmp->db_agsize);
     l2nl =
         bmp->db_agl2size - (L2BPERDMAP + bmp->db_aglevel * L2LPERCTL);
     bmp->db_agheight = l2nl >> 1;
     bmp->db_agwidth = 1 << (l2nl - (bmp->db_agheight << 1));
     for (i = 5 - bmp->db_agheight, bmp->db_agstart = 0, n = 1; i > 0;
          i--) {
         bmp->db_agstart += n;
         n <<= 2;
     }
 
 }
 
 
 /*
  * NAME:    dbInitDmap()/ujfs_idmap_page()
  *
  * FUNCTION:    initialize working/persistent bitmap of the dmap page
  *      for the specified number of blocks:
  *
  *      at entry, the bitmaps had been initialized as free (ZEROS);
  *      The number of blocks will only account for the actually
  *      existing blocks. Blocks which don't actually exist in
  *      the aggregate will be marked as allocated (ONES);
  *
  * PARAMETERS:
  *  dp  - pointer to page of map
  *  nblocks - number of blocks this page
  *
  * RETURNS: NONE
  */
 static int dbInitDmap(struct dmap * dp, s64 Blkno, int nblocks)
 {
     int blkno, w, b, r, nw, nb, i;
 
     /* starting block number within the dmap */
     blkno = Blkno & (BPERDMAP - 1);
 
     if (blkno == 0) {
         dp->nblocks = dp->nfree = cpu_to_le32(nblocks);
         dp->start = cpu_to_le64(Blkno);
 
         if (nblocks == BPERDMAP) {
             memset(&dp->wmap[0], 0, LPERDMAP * 4);
             memset(&dp->pmap[0], 0, LPERDMAP * 4);
             goto initTree;
         }
     } else {
         le32_add_cpu(&dp->nblocks, nblocks);
         le32_add_cpu(&dp->nfree, nblocks);
     }
 
     /* word number containing start block number */
     w = blkno >> L2DBWORD;
 
     /*
      * free the bits corresponding to the block range (ZEROS):
      * note: not all bits of the first and last words may be contained
      * within the block range.
      */
     for (r = nblocks; r > 0; r -= nb, blkno += nb) {
         /* number of bits preceding range to be freed in the word */
         b = blkno & (DBWORD - 1);
         /* number of bits to free in the word */
         nb = min(r, DBWORD - b);
 
         /* is partial word to be freed ? */
         if (nb < DBWORD) {
             /* free (set to 0) from the bitmap word */
             dp->wmap[w] &= cpu_to_le32(~(ONES << (DBWORD - nb)
                              >> b));
             dp->pmap[w] &= cpu_to_le32(~(ONES << (DBWORD - nb)
                              >> b));
 
             /* skip the word freed */
             w++;
         } else {
             /* free (set to 0) contiguous bitmap words */
             nw = r >> L2DBWORD;
             memset(&dp->wmap[w], 0, nw * 4);
             memset(&dp->pmap[w], 0, nw * 4);
 
             /* skip the words freed */
             nb = nw << L2DBWORD;
             w += nw;
         }
     }
 
     /*
      * mark bits following the range to be freed (non-existing
      * blocks) as allocated (ONES)
      */
 
     if (blkno == BPERDMAP)
         goto initTree;
 
     /* the first word beyond the end of existing blocks */
     w = blkno >> L2DBWORD;
 
     /* does nblocks fall on a 32-bit boundary ? */
     b = blkno & (DBWORD - 1);
     if (b) {
         /* mark a partial word allocated */
         dp->wmap[w] = dp->pmap[w] = cpu_to_le32(ONES >> b);
         w++;
     }
 
     /* set the rest of the words in the page to allocated (ONES) */
     for (i = w; i < LPERDMAP; i++)
         dp->pmap[i] = dp->wmap[i] = cpu_to_le32(ONES);
 
     /*
      * init tree
      */
       initTree:
     return (dbInitDmapTree(dp));
 }
 
 
 /*
  * NAME:    dbInitDmapTree()/ujfs_complete_dmap()
  *
  * FUNCTION:    initialize summary tree of the specified dmap:
  *
  *      at entry, bitmap of the dmap has been initialized;
  *
  * PARAMETERS:
  *  dp  - dmap to complete
  *  blkno   - starting block number for this dmap
  *  treemax - will be filled in with max free for this dmap
  *
  * RETURNS: max free string at the root of the tree
  */
 static int dbInitDmapTree(struct dmap * dp)
 {
     struct dmaptree *tp;
     s8 *cp;
     int i;
 
     /* init fixed info of tree */
     tp = &dp->tree;
     tp->nleafs = cpu_to_le32(LPERDMAP);
     tp->l2nleafs = cpu_to_le32(L2LPERDMAP);
     tp->leafidx = cpu_to_le32(LEAFIND);
     tp->height = cpu_to_le32(4);
     tp->budmin = BUDMIN;
 
     /* init each leaf from corresponding wmap word:
      * note: leaf is set to NOFREE(-1) if all blocks of corresponding
      * bitmap word are allocated.
      */
     cp = tp->stree + le32_to_cpu(tp->leafidx);
     for (i = 0; i < LPERDMAP; i++)
         *cp++ = dbMaxBud((u8 *) & dp->wmap[i]);
 
     /* build the dmap's binary buddy summary tree */
     return (dbInitTree(tp));
 }
 
 
 /*
  * NAME:    dbInitTree()/ujfs_adjtree()
  *
  * FUNCTION:    initialize binary buddy summary tree of a dmap or dmapctl.
  *
  *      at entry, the leaves of the tree has been initialized
  *      from corresponding bitmap word or root of summary tree
  *      of the child control page;
  *      configure binary buddy system at the leaf level, then
  *      bubble up the values of the leaf nodes up the tree.
  *
  * PARAMETERS:
  *  cp  - Pointer to the root of the tree
  *  l2leaves- Number of leaf nodes as a power of 2
  *  l2min   - Number of blocks that can be covered by a leaf
  *        as a power of 2
  *
  * RETURNS: max free string at the root of the tree
  */
 static int dbInitTree(struct dmaptree * dtp)
 {
     int l2max, l2free, bsize, nextb, i;
     int child, parent, nparent;
     s8 *tp, *cp, *cp1;
 
     tp = dtp->stree;
 
     /* Determine the maximum free string possible for the leaves */
     l2max = le32_to_cpu(dtp->l2nleafs) + dtp->budmin;
 
     /*
      * configure the leaf levevl into binary buddy system
      *
      * Try to combine buddies starting with a buddy size of 1
      * (i.e. two leaves). At a buddy size of 1 two buddy leaves
      * can be combined if both buddies have a maximum free of l2min;
      * the combination will result in the left-most buddy leaf having
      * a maximum free of l2min+1.
      * After processing all buddies for a given size, process buddies
      * at the next higher buddy size (i.e. current size * 2) and
      * the next maximum free (current free + 1).
      * This continues until the maximum possible buddy combination
      * yields maximum free.
      */
     for (l2free = dtp->budmin, bsize = 1; l2free < l2max;
          l2free++, bsize = nextb) {
         /* get next buddy size == current buddy pair size */
         nextb = bsize << 1;
 
         /* scan each adjacent buddy pair at current buddy size */
         for (i = 0, cp = tp + le32_to_cpu(dtp->leafidx);
              i < le32_to_cpu(dtp->nleafs);
              i += nextb, cp += nextb) {
             /* coalesce if both adjacent buddies are max free */
             if (*cp == l2free && *(cp + bsize) == l2free) {
                 *cp = l2free + 1;   /* left take right */
                 *(cp + bsize) = -1; /* right give left */
             }
         }
     }
 
     /*
      * bubble summary information of leaves up the tree.
      *
      * Starting at the leaf node level, the four nodes described by
      * the higher level parent node are compared for a maximum free and
      * this maximum becomes the value of the parent node.
      * when all lower level nodes are processed in this fashion then
      * move up to the next level (parent becomes a lower level node) and
      * continue the process for that level.
      */
     for (child = le32_to_cpu(dtp->leafidx),
          nparent = le32_to_cpu(dtp->nleafs) >> 2;
          nparent > 0; nparent >>= 2, child = parent) {
         /* get index of 1st node of parent level */
         parent = (child - 1) >> 2;
 
         /* set the value of the parent node as the maximum
          * of the four nodes of the current level.
          */
         for (i = 0, cp = tp + child, cp1 = tp + parent;
              i < nparent; i++, cp += 4, cp1++)
             *cp1 = TREEMAX(cp);
     }
 
     return (*tp);
 }
 
 
 /*
  *  dbInitDmapCtl()
  *
  * function: initialize dmapctl page
  */
 static int dbInitDmapCtl(struct dmapctl * dcp, int level, int i)
 {               /* start leaf index not covered by range */
     s8 *cp;
 
     dcp->nleafs = cpu_to_le32(LPERCTL);
     dcp->l2nleafs = cpu_to_le32(L2LPERCTL);
     dcp->leafidx = cpu_to_le32(CTLLEAFIND);
     dcp->height = cpu_to_le32(5);
     dcp->budmin = L2BPERDMAP + L2LPERCTL * level;
 
     /*
      * initialize the leaves of current level that were not covered
      * by the specified input block range (i.e. the leaves have no
      * low level dmapctl or dmap).
      */
     cp = &dcp->stree[CTLLEAFIND + i];
     for (; i < LPERCTL; i++)
         *cp++ = NOFREE;
 
     /* build the dmap's binary buddy summary tree */
     return (dbInitTree((struct dmaptree *) dcp));
 }
 
 
 /*
  * NAME:    dbGetL2AGSize()/ujfs_getagl2size()
  *
  * FUNCTION:    Determine log2(allocation group size) from aggregate size
  *
  * PARAMETERS:
  *  nblocks - Number of blocks in aggregate
  *
  * RETURNS: log2(allocation group size) in aggregate blocks
  */
 static int dbGetL2AGSize(s64 nblocks)
 {
     s64 sz;
     s64 m;
     int l2sz;
 
     if (nblocks < BPERDMAP * MAXAG)
         return (L2BPERDMAP);
 
     /* round up aggregate size to power of 2 */
     m = ((u64) 1 << (64 - 1));
     for (l2sz = 64; l2sz >= 0; l2sz--, m >>= 1) {
         if (m & nblocks)
             break;
     }
 
     sz = (s64) 1 << l2sz;
     if (sz < nblocks)
         l2sz += 1;
 
     /* agsize = roundupSize/max_number_of_ag */
     return (l2sz - L2MAXAG);
 }
 
 
 /*
  * NAME:    dbMapFileSizeToMapSize()
  *
  * FUNCTION:    compute number of blocks the block allocation map file
  *      can cover from the map file size;
  *
  * RETURNS: Number of blocks which can be covered by this block map file;
  */
 
 /*
  * maximum number of map pages at each level including control pages
  */
 #define MAXL0PAGES  (1 + LPERCTL)
 #define MAXL1PAGES  (1 + LPERCTL * MAXL0PAGES)
 
 /*
  * convert number of map pages to the zero origin top dmapctl level
  */
 #define BMAPPGTOLEV(npages) \
     (((npages) <= 3 + MAXL0PAGES) ? 0 : \
      ((npages) <= 2 + MAXL1PAGES) ? 1 : 2)
 
 s64 dbMapFileSizeToMapSize(struct inode * ipbmap)
 {
     struct super_block *sb = ipbmap->i_sb;
     s64 nblocks;
     s64 npages, ndmaps;
     int level, i;
     int complete, factor;
 
     nblocks = ipbmap->i_size >> JFS_SBI(sb)->l2bsize;
     npages = nblocks >> JFS_SBI(sb)->l2nbperpage;
     level = BMAPPGTOLEV(npages);
 
     /* At each level, accumulate the number of dmap pages covered by
      * the number of full child levels below it;
      * repeat for the last incomplete child level.
      */
     ndmaps = 0;
     npages--;       /* skip the first global control page */
     /* skip higher level control pages above top level covered by map */
     npages -= (2 - level);
     npages--;       /* skip top level's control page */
     for (i = level; i >= 0; i--) {
         factor =
             (i == 2) ? MAXL1PAGES : ((i == 1) ? MAXL0PAGES : 1);
         complete = (u32) npages / factor;
         ndmaps += complete * ((i == 2) ? LPERCTL * LPERCTL :
                       ((i == 1) ? LPERCTL : 1));
 
         /* pages in last/incomplete child */
         npages = (u32) npages % factor;
         /* skip incomplete child's level control page */
         npages--;
     }
 
     /* convert the number of dmaps into the number of blocks
      * which can be covered by the dmaps;
      */
     nblocks = ndmaps << L2BPERDMAP;
 
     return (nblocks);
 }