jfs_dmap.c

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/*
 *   Copyright (C) International Business Machines Corp., 2000-2004
 *   Portions Copyright (C) Tino Reichardt, 2012
 *
 *   This program is free software;  you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY;  without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
 *   the GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program;  if not, write to the Free Software
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

#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
 */
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);
    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,
              "dbFree: block to be freed is outside the map");
        return -EIO;
    }

    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, "dbFree: error in block map\n");
            release_metapage(mp);
            IREAD_UNLOCK(ipbmap);
            return (rc);
        }
    }

    /* write the last buffer. */
    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,
              "dbUpdatePMap: blocks are outside the map");
        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
 *      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, "dbAlloc: the hint is outside the map");
        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);
}

#ifdef _NOTYET
/*
 * NAME:    dbAllocExact()
 *
 * FUNCTION:    try to allocate the requested extent;
 *
 * PARAMETERS:
 *  ip  - pointer to in-core inode;
 *  blkno   - extent address;
 *  nblocks - extent length;
 *
 * RETURN VALUES:
 *  0   - success
 *  -ENOSPC - insufficient disk resources
 *  -EIO    - i/o error
 */
int dbAllocExact(struct inode *ip, s64 blkno, int nblocks)
{
    int rc;
    struct inode *ipbmap = JFS_SBI(ip->i_sb)->ipbmap;
    struct bmap *bmp = JFS_SBI(ip->i_sb)->bmap;
    struct dmap *dp;
    s64 lblkno;
    struct metapage *mp;

    IREAD_LOCK(ipbmap, RDWRLOCK_DMAP);

    /*
     * validate extent request:
     *
     * note: defragfs policy:
     *  max 64 blocks will be moved.
     *  allocation request size must be satisfied from a single dmap.
     */
    if (nblocks <= 0 || nblocks > BPERDMAP || blkno >= bmp->db_mapsize) {
        IREAD_UNLOCK(ipbmap);
        return -EINVAL;
    }

    if (nblocks > ((s64) 1 << bmp->db_maxfreebud)) {
        /* the free space is no longer available */
        IREAD_UNLOCK(ipbmap);
        return -ENOSPC;
    }

    /* read in the dmap covering the extent */
    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;

    /* try to allocate the requested extent */
    rc = dbAllocNext(bmp, dp, blkno, nblocks);

    IREAD_UNLOCK(ipbmap);

    if (rc == 0)
        mark_metapage_dirty(mp);

    release_metapage(mp);

    return (rc);
}
#endif /* _NOTYET */

/*
 * 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,
              "dbExtend: the block is outside the filesystem");
        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,
              "dbAllocNext: Corrupt dmap page");
        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((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,
              "dbAllocNear: Corrupt dmap page");
        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,
              "dbAllocAG: allocation request is larger than the "
              "allocation group size");
        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,
                  "dbAllocAG: dbAllocCtl failed in free AG");
        }
        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,
              "dbAllocAG: Corrupt dmapctl page");
        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,
                      "dbAllocAG: failed descending stree");
                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,
                          "dbAllocAG: control page "
                          "inconsistent");
                    return -EIO;
                }
                return (rc);
            }
        }

        /* allocate the blocks.
         */
        rc = dbAllocCtl(bmp, nblocks, l2nb, blkno, results);
        if (rc == -ENOSPC) {
            jfs_error(bmp->db_ipbmap->i_sb,
                  "dbAllocAG: unable to allocate blocks");
            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,
              "dbAllocAny: unable to allocate blocks");
        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(sizeof(struct range2trim) * range_cnt, GFP_NOFS);
    if (totrim == NULL) {
        jfs_error(bmp->db_ipbmap->i_sb,
              "dbDiscardAG: no memory for trim array");
        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 = 1 << l2nb;
        } else {
            /* Trim any already allocated blocks */
            jfs_error(bmp->db_ipbmap->i_sb,
                "dbDiscardAG: -EIO");
            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,
                  "dbFindCtl: Corrupt dmapctl page");
            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,
                      "dbFindCtl: dmap inconsistent");
                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,
                  "dbAllocCtl: the dmap is not all free");
            rc = -EIO;
            goto backout;
        }

        /* determine how many blocks to allocate from this dmap.
         */
        nb = min(n, (s64)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,
                  "dbAllocCtl: I/O Error: Block Leakage.");
            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,
                  "dbAllocCtl: Block Leakage.");
            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,
                          "dbAllocBits: leaf page "
                          "corrupt");
                    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((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,
              "dbAdjCtl: Corrupt dmapctl page");
        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)
                return rc;
            oldval = dcp->stree[ti];
        }
        dbSplit((dmtree_t *) dcp, leafno, dcp->budmin, newval);
    } else {
        rc = dbJoin((dmtree_t *) dcp, leafno, newval);
        if (rc)
            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,
                      "dbAdjCtl: the maximum free buddy is "
                      "not the old root");
            }
            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, "dbExtendFS: L2 page could not be read");
        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(nblocks, (s64)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,
          "dbExtendFS: function has not returned as expected");
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 inacitve 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");
        }
    }

    /*
     * 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)
#define MAXL2PAGES  (1 + LPERCTL * MAXL1PAGES)

/*
 * 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);
}