xfs: fix potential infinite loop in xfs_iomap_prealloc_size()

[deliverable/linux.git] / fs / xfs / xfs_dir2_block.c

/*
 * Copyright (c) 2000-2003,2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * 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.
 *
 * This program is distributed in the hope that it would 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 the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_types.h"
#include "xfs_log.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_mount.h"
#include "xfs_da_btree.h"
#include "xfs_bmap_btree.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_inode_item.h"
#include "xfs_dir2.h"
#include "xfs_dir2_format.h"
#include "xfs_dir2_priv.h"
#include "xfs_error.h"
#include "xfs_trace.h"

/*
 * Local function prototypes.
 */
static void xfs_dir2_block_log_leaf(xfs_trans_t *tp, struct xfs_buf *bp,
                                    int first, int last);
static void xfs_dir2_block_log_tail(xfs_trans_t *tp, struct xfs_buf *bp);
static int xfs_dir2_block_lookup_int(xfs_da_args_t *args, struct xfs_buf **bpp,
                                     int *entno);
static int xfs_dir2_block_sort(const void *a, const void *b);

static xfs_dahash_t xfs_dir_hash_dot, xfs_dir_hash_dotdot;

/*
 * One-time startup routine called from xfs_init().
 */
void
xfs_dir_startup(void)
{
        xfs_dir_hash_dot = xfs_da_hashname((unsigned char *)".", 1);
        xfs_dir_hash_dotdot = xfs_da_hashname((unsigned char *)"..", 2);
}

static void
xfs_dir2_block_verify(
        struct xfs_buf          *bp)
{
        struct xfs_mount        *mp = bp->b_target->bt_mount;
        struct xfs_dir2_data_hdr *hdr = bp->b_addr;
        int                     block_ok = 0;

        block_ok = hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC);
        block_ok = block_ok && __xfs_dir2_data_check(NULL, bp) == 0;

        if (!block_ok) {
                XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, hdr);
                xfs_buf_ioerror(bp, EFSCORRUPTED);
        }
}

static void
xfs_dir2_block_read_verify(
        struct xfs_buf  *bp)
{
        xfs_dir2_block_verify(bp);
}

static void
xfs_dir2_block_write_verify(
        struct xfs_buf  *bp)
{
        xfs_dir2_block_verify(bp);
}

const struct xfs_buf_ops xfs_dir2_block_buf_ops = {
        .verify_read = xfs_dir2_block_read_verify,
        .verify_write = xfs_dir2_block_write_verify,
};

static int
xfs_dir2_block_read(
        struct xfs_trans        *tp,
        struct xfs_inode        *dp,
        struct xfs_buf          **bpp)
{
        struct xfs_mount        *mp = dp->i_mount;

        return xfs_da_read_buf(tp, dp, mp->m_dirdatablk, -1, bpp,
                                XFS_DATA_FORK, &xfs_dir2_block_buf_ops);
}

static void
xfs_dir2_block_need_space(
        struct xfs_dir2_data_hdr        *hdr,
        struct xfs_dir2_block_tail      *btp,
        struct xfs_dir2_leaf_entry      *blp,
        __be16                          **tagpp,
        struct xfs_dir2_data_unused     **dupp,
        struct xfs_dir2_data_unused     **enddupp,
        int                             *compact,
        int                             len)
{
        struct xfs_dir2_data_free       *bf;
        __be16                          *tagp = NULL;
        struct xfs_dir2_data_unused     *dup = NULL;
        struct xfs_dir2_data_unused     *enddup = NULL;

        *compact = 0;
        bf = hdr->bestfree;

        /*
         * If there are stale entries we'll use one for the leaf.
         */
        if (btp->stale) {
                if (be16_to_cpu(bf[0].length) >= len) {
                        /*
                         * The biggest entry enough to avoid compaction.
                         */
                        dup = (xfs_dir2_data_unused_t *)
                              ((char *)hdr + be16_to_cpu(bf[0].offset));
                        goto out;
                }

                /*
                 * Will need to compact to make this work.
                 * Tag just before the first leaf entry.
                 */
                *compact = 1;
                tagp = (__be16 *)blp - 1;

                /* Data object just before the first leaf entry.  */
                dup = (xfs_dir2_data_unused_t *)((char *)hdr + be16_to_cpu(*tagp));

                /*
                 * If it's not free then the data will go where the
                 * leaf data starts now, if it works at all.
                 */
                if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
                        if (be16_to_cpu(dup->length) + (be32_to_cpu(btp->stale) - 1) *
                            (uint)sizeof(*blp) < len)
                                dup = NULL;
                } else if ((be32_to_cpu(btp->stale) - 1) * (uint)sizeof(*blp) < len)
                        dup = NULL;
                else
                        dup = (xfs_dir2_data_unused_t *)blp;
                goto out;
        }

        /*
         * no stale entries, so just use free space.
         * Tag just before the first leaf entry.
         */
        tagp = (__be16 *)blp - 1;

        /* Data object just before the first leaf entry.  */
        enddup = (xfs_dir2_data_unused_t *)((char *)hdr + be16_to_cpu(*tagp));

        /*
         * If it's not free then can't do this add without cleaning up:
         * the space before the first leaf entry needs to be free so it
         * can be expanded to hold the pointer to the new entry.
         */
        if (be16_to_cpu(enddup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
                /*
                 * Check out the biggest freespace and see if it's the same one.
                 */
                dup = (xfs_dir2_data_unused_t *)
                      ((char *)hdr + be16_to_cpu(bf[0].offset));
                if (dup != enddup) {
                        /*
                         * Not the same free entry, just check its length.
                         */
                        if (be16_to_cpu(dup->length) < len)
                                dup = NULL;
                        goto out;
                }

                /*
                 * It is the biggest freespace, can it hold the leaf too?
                 */
                if (be16_to_cpu(dup->length) < len + (uint)sizeof(*blp)) {
                        /*
                         * Yes, use the second-largest entry instead if it works.
                         */
                        if (be16_to_cpu(bf[1].length) >= len)
                                dup = (xfs_dir2_data_unused_t *)
                                      ((char *)hdr + be16_to_cpu(bf[1].offset));
                        else
                                dup = NULL;
                }
        }
out:
        *tagpp = tagp;
        *dupp = dup;
        *enddupp = enddup;
}

/*
 * compact the leaf entries.
 * Leave the highest-numbered stale entry stale.
 * XXX should be the one closest to mid but mid is not yet computed.
 */
static void
xfs_dir2_block_compact(
        struct xfs_trans                *tp,
        struct xfs_buf                  *bp,
        struct xfs_dir2_data_hdr        *hdr,
        struct xfs_dir2_block_tail      *btp,
        struct xfs_dir2_leaf_entry      *blp,
        int                             *needlog,
        int                             *lfloghigh,
        int                             *lfloglow)
{
        int                     fromidx;        /* source leaf index */
        int                     toidx;          /* target leaf index */
        int                     needscan = 0;
        int                     highstale;      /* high stale index */

        fromidx = toidx = be32_to_cpu(btp->count) - 1;
        highstale = *lfloghigh = -1;
        for (; fromidx >= 0; fromidx--) {
                if (blp[fromidx].address == cpu_to_be32(XFS_DIR2_NULL_DATAPTR)) {
                        if (highstale == -1)
                                highstale = toidx;
                        else {
                                if (*lfloghigh == -1)
                                        *lfloghigh = toidx;
                                continue;
                        }
                }
                if (fromidx < toidx)
                        blp[toidx] = blp[fromidx];
                toidx--;
        }
        *lfloglow = toidx + 1 - (be32_to_cpu(btp->stale) - 1);
        *lfloghigh -= be32_to_cpu(btp->stale) - 1;
        be32_add_cpu(&btp->count, -(be32_to_cpu(btp->stale) - 1));
        xfs_dir2_data_make_free(tp, bp,
                (xfs_dir2_data_aoff_t)((char *)blp - (char *)hdr),
                (xfs_dir2_data_aoff_t)((be32_to_cpu(btp->stale) - 1) * sizeof(*blp)),
                needlog, &needscan);
        blp += be32_to_cpu(btp->stale) - 1;
        btp->stale = cpu_to_be32(1);
        /*
         * If we now need to rebuild the bestfree map, do so.
         * This needs to happen before the next call to use_free.
         */
        if (needscan)
                xfs_dir2_data_freescan(tp->t_mountp, hdr, needlog);
}

/*
 * Add an entry to a block directory.
 */
int                                             /* error */
xfs_dir2_block_addname(
        xfs_da_args_t           *args)          /* directory op arguments */
{
        xfs_dir2_data_hdr_t     *hdr;           /* block header */
        xfs_dir2_leaf_entry_t   *blp;           /* block leaf entries */
        struct xfs_buf          *bp;            /* buffer for block */
        xfs_dir2_block_tail_t   *btp;           /* block tail */
        int                     compact;        /* need to compact leaf ents */
        xfs_dir2_data_entry_t   *dep;           /* block data entry */
        xfs_inode_t             *dp;            /* directory inode */
        xfs_dir2_data_unused_t  *dup;           /* block unused entry */
        int                     error;          /* error return value */
        xfs_dir2_data_unused_t  *enddup=NULL;   /* unused at end of data */
        xfs_dahash_t            hash;           /* hash value of found entry */
        int                     high;           /* high index for binary srch */
        int                     highstale;      /* high stale index */
        int                     lfloghigh=0;    /* last final leaf to log */
        int                     lfloglow=0;     /* first final leaf to log */
        int                     len;            /* length of the new entry */
        int                     low;            /* low index for binary srch */
        int                     lowstale;       /* low stale index */
        int                     mid=0;          /* midpoint for binary srch */
        xfs_mount_t             *mp;            /* filesystem mount point */
        int                     needlog;        /* need to log header */
        int                     needscan;       /* need to rescan freespace */
        __be16                  *tagp;          /* pointer to tag value */
        xfs_trans_t             *tp;            /* transaction structure */

        trace_xfs_dir2_block_addname(args);

        dp = args->dp;
        tp = args->trans;
        mp = dp->i_mount;

        /* Read the (one and only) directory block into bp. */
        error = xfs_dir2_block_read(tp, dp, &bp);
        if (error)
                return error;

        len = xfs_dir2_data_entsize(args->namelen);

        /*
         * Set up pointers to parts of the block.
         */
        hdr = bp->b_addr;
        btp = xfs_dir2_block_tail_p(mp, hdr);
        blp = xfs_dir2_block_leaf_p(btp);

        /*
         * Find out if we can reuse stale entries or whether we need extra
         * space for entry and new leaf.
         */
        xfs_dir2_block_need_space(hdr, btp, blp, &tagp, &dup,
                                  &enddup, &compact, len);

        /*
         * Done everything we need for a space check now.
         */
        if (args->op_flags & XFS_DA_OP_JUSTCHECK) {
                xfs_trans_brelse(tp, bp);
                if (!dup)
                        return XFS_ERROR(ENOSPC);
                return 0;
        }

        /*
         * If we don't have space for the new entry & leaf ...
         */
        if (!dup) {
                /* Don't have a space reservation: return no-space.  */
                if (args->total == 0)
                        return XFS_ERROR(ENOSPC);
                /*
                 * Convert to the next larger format.
                 * Then add the new entry in that format.
                 */
                error = xfs_dir2_block_to_leaf(args, bp);
                if (error)
                        return error;
                return xfs_dir2_leaf_addname(args);
        }

        needlog = needscan = 0;

        /*
         * If need to compact the leaf entries, do it now.
         */
        if (compact) {
                xfs_dir2_block_compact(tp, bp, hdr, btp, blp, &needlog,
                                      &lfloghigh, &lfloglow);
                /* recalculate blp post-compaction */
                blp = xfs_dir2_block_leaf_p(btp);
        } else if (btp->stale) {
                /*
                 * Set leaf logging boundaries to impossible state.
                 * For the no-stale case they're set explicitly.
                 */
                lfloglow = be32_to_cpu(btp->count);
                lfloghigh = -1;
        }

        /*
         * Find the slot that's first lower than our hash value, -1 if none.
         */
        for (low = 0, high = be32_to_cpu(btp->count) - 1; low <= high; ) {
                mid = (low + high) >> 1;
                if ((hash = be32_to_cpu(blp[mid].hashval)) == args->hashval)
                        break;
                if (hash < args->hashval)
                        low = mid + 1;
                else
                        high = mid - 1;
        }
        while (mid >= 0 && be32_to_cpu(blp[mid].hashval) >= args->hashval) {
                mid--;
        }
        /*
         * No stale entries, will use enddup space to hold new leaf.
         */
        if (!btp->stale) {
                /*
                 * Mark the space needed for the new leaf entry, now in use.
                 */
                xfs_dir2_data_use_free(tp, bp, enddup,
                        (xfs_dir2_data_aoff_t)
                        ((char *)enddup - (char *)hdr + be16_to_cpu(enddup->length) -
                         sizeof(*blp)),
                        (xfs_dir2_data_aoff_t)sizeof(*blp),
                        &needlog, &needscan);
                /*
                 * Update the tail (entry count).
                 */
                be32_add_cpu(&btp->count, 1);
                /*
                 * If we now need to rebuild the bestfree map, do so.
                 * This needs to happen before the next call to use_free.
                 */
                if (needscan) {
                        xfs_dir2_data_freescan(mp, hdr, &needlog);
                        needscan = 0;
                }
                /*
                 * Adjust pointer to the first leaf entry, we're about to move
                 * the table up one to open up space for the new leaf entry.
                 * Then adjust our index to match.
                 */
                blp--;
                mid++;
                if (mid)
                        memmove(blp, &blp[1], mid * sizeof(*blp));
                lfloglow = 0;
                lfloghigh = mid;
        }
        /*
         * Use a stale leaf for our new entry.
         */
        else {
                for (lowstale = mid;
                     lowstale >= 0 &&
                        blp[lowstale].address !=
                        cpu_to_be32(XFS_DIR2_NULL_DATAPTR);
                     lowstale--)
                        continue;
                for (highstale = mid + 1;
                     highstale < be32_to_cpu(btp->count) &&
                        blp[highstale].address !=
                        cpu_to_be32(XFS_DIR2_NULL_DATAPTR) &&
                        (lowstale < 0 || mid - lowstale > highstale - mid);
                     highstale++)
                        continue;
                /*
                 * Move entries toward the low-numbered stale entry.
                 */
                if (lowstale >= 0 &&
                    (highstale == be32_to_cpu(btp->count) ||
                     mid - lowstale <= highstale - mid)) {
                        if (mid - lowstale)
                                memmove(&blp[lowstale], &blp[lowstale + 1],
                                        (mid - lowstale) * sizeof(*blp));
                        lfloglow = MIN(lowstale, lfloglow);
                        lfloghigh = MAX(mid, lfloghigh);
                }
                /*
                 * Move entries toward the high-numbered stale entry.
                 */
                else {
                        ASSERT(highstale < be32_to_cpu(btp->count));
                        mid++;
                        if (highstale - mid)
                                memmove(&blp[mid + 1], &blp[mid],
                                        (highstale - mid) * sizeof(*blp));
                        lfloglow = MIN(mid, lfloglow);
                        lfloghigh = MAX(highstale, lfloghigh);
                }
                be32_add_cpu(&btp->stale, -1);
        }
        /*
         * Point to the new data entry.
         */
        dep = (xfs_dir2_data_entry_t *)dup;
        /*
         * Fill in the leaf entry.
         */
        blp[mid].hashval = cpu_to_be32(args->hashval);
        blp[mid].address = cpu_to_be32(xfs_dir2_byte_to_dataptr(mp,
                                (char *)dep - (char *)hdr));
        xfs_dir2_block_log_leaf(tp, bp, lfloglow, lfloghigh);
        /*
         * Mark space for the data entry used.
         */
        xfs_dir2_data_use_free(tp, bp, dup,
                (xfs_dir2_data_aoff_t)((char *)dup - (char *)hdr),
                (xfs_dir2_data_aoff_t)len, &needlog, &needscan);
        /*
         * Create the new data entry.
         */
        dep->inumber = cpu_to_be64(args->inumber);
        dep->namelen = args->namelen;
        memcpy(dep->name, args->name, args->namelen);
        tagp = xfs_dir2_data_entry_tag_p(dep);
        *tagp = cpu_to_be16((char *)dep - (char *)hdr);
        /*
         * Clean up the bestfree array and log the header, tail, and entry.
         */
        if (needscan)
                xfs_dir2_data_freescan(mp, hdr, &needlog);
        if (needlog)
                xfs_dir2_data_log_header(tp, bp);
        xfs_dir2_block_log_tail(tp, bp);
        xfs_dir2_data_log_entry(tp, bp, dep);
        xfs_dir2_data_check(dp, bp);
        return 0;
}

/*
 * Readdir for block directories.
 */
int                                             /* error */
xfs_dir2_block_getdents(
        xfs_inode_t             *dp,            /* incore inode */
        void                    *dirent,
        xfs_off_t               *offset,
        filldir_t               filldir)
{
        xfs_dir2_data_hdr_t     *hdr;           /* block header */
        struct xfs_buf          *bp;            /* buffer for block */
        xfs_dir2_block_tail_t   *btp;           /* block tail */
        xfs_dir2_data_entry_t   *dep;           /* block data entry */
        xfs_dir2_data_unused_t  *dup;           /* block unused entry */
        char                    *endptr;        /* end of the data entries */
        int                     error;          /* error return value */
        xfs_mount_t             *mp;            /* filesystem mount point */
        char                    *ptr;           /* current data entry */
        int                     wantoff;        /* starting block offset */
        xfs_off_t               cook;

        mp = dp->i_mount;
        /*
         * If the block number in the offset is out of range, we're done.
         */
        if (xfs_dir2_dataptr_to_db(mp, *offset) > mp->m_dirdatablk)
                return 0;

        error = xfs_dir2_block_read(NULL, dp, &bp);
        if (error)
                return error;

        /*
         * Extract the byte offset we start at from the seek pointer.
         * We'll skip entries before this.
         */
        wantoff = xfs_dir2_dataptr_to_off(mp, *offset);
        hdr = bp->b_addr;
        xfs_dir2_data_check(dp, bp);
        /*
         * Set up values for the loop.
         */
        btp = xfs_dir2_block_tail_p(mp, hdr);
        ptr = (char *)(hdr + 1);
        endptr = (char *)xfs_dir2_block_leaf_p(btp);

        /*
         * Loop over the data portion of the block.
         * Each object is a real entry (dep) or an unused one (dup).
         */
        while (ptr < endptr) {
                dup = (xfs_dir2_data_unused_t *)ptr;
                /*
                 * Unused, skip it.
                 */
                if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
                        ptr += be16_to_cpu(dup->length);
                        continue;
                }

                dep = (xfs_dir2_data_entry_t *)ptr;

                /*
                 * Bump pointer for the next iteration.
                 */
                ptr += xfs_dir2_data_entsize(dep->namelen);
                /*
                 * The entry is before the desired starting point, skip it.
                 */
                if ((char *)dep - (char *)hdr < wantoff)
                        continue;

                cook = xfs_dir2_db_off_to_dataptr(mp, mp->m_dirdatablk,
                                            (char *)dep - (char *)hdr);

                /*
                 * If it didn't fit, set the final offset to here & return.
                 */
                if (filldir(dirent, (char *)dep->name, dep->namelen,
                            cook & 0x7fffffff, be64_to_cpu(dep->inumber),
                            DT_UNKNOWN)) {
                        *offset = cook & 0x7fffffff;
                        xfs_trans_brelse(NULL, bp);
                        return 0;
                }
        }

        /*
         * Reached the end of the block.
         * Set the offset to a non-existent block 1 and return.
         */
        *offset = xfs_dir2_db_off_to_dataptr(mp, mp->m_dirdatablk + 1, 0) &
                        0x7fffffff;
        xfs_trans_brelse(NULL, bp);
        return 0;
}

/*
 * Log leaf entries from the block.
 */
static void
xfs_dir2_block_log_leaf(
        xfs_trans_t             *tp,            /* transaction structure */
        struct xfs_buf          *bp,            /* block buffer */
        int                     first,          /* index of first logged leaf */
        int                     last)           /* index of last logged leaf */
{
        xfs_dir2_data_hdr_t     *hdr = bp->b_addr;
        xfs_dir2_leaf_entry_t   *blp;
        xfs_dir2_block_tail_t   *btp;

        btp = xfs_dir2_block_tail_p(tp->t_mountp, hdr);
        blp = xfs_dir2_block_leaf_p(btp);
        xfs_trans_log_buf(tp, bp, (uint)((char *)&blp[first] - (char *)hdr),
                (uint)((char *)&blp[last + 1] - (char *)hdr - 1));
}

/*
 * Log the block tail.
 */
static void
xfs_dir2_block_log_tail(
        xfs_trans_t             *tp,            /* transaction structure */
        struct xfs_buf          *bp)            /* block buffer */
{
        xfs_dir2_data_hdr_t     *hdr = bp->b_addr;
        xfs_dir2_block_tail_t   *btp;

        btp = xfs_dir2_block_tail_p(tp->t_mountp, hdr);
        xfs_trans_log_buf(tp, bp, (uint)((char *)btp - (char *)hdr),
                (uint)((char *)(btp + 1) - (char *)hdr - 1));
}

/*
 * Look up an entry in the block.  This is the external routine,
 * xfs_dir2_block_lookup_int does the real work.
 */
int                                             /* error */
xfs_dir2_block_lookup(
        xfs_da_args_t           *args)          /* dir lookup arguments */
{
        xfs_dir2_data_hdr_t     *hdr;           /* block header */
        xfs_dir2_leaf_entry_t   *blp;           /* block leaf entries */
        struct xfs_buf          *bp;            /* block buffer */
        xfs_dir2_block_tail_t   *btp;           /* block tail */
        xfs_dir2_data_entry_t   *dep;           /* block data entry */
        xfs_inode_t             *dp;            /* incore inode */
        int                     ent;            /* entry index */
        int                     error;          /* error return value */
        xfs_mount_t             *mp;            /* filesystem mount point */

        trace_xfs_dir2_block_lookup(args);

        /*
         * Get the buffer, look up the entry.
         * If not found (ENOENT) then return, have no buffer.
         */
        if ((error = xfs_dir2_block_lookup_int(args, &bp, &ent)))
                return error;
        dp = args->dp;
        mp = dp->i_mount;
        hdr = bp->b_addr;
        xfs_dir2_data_check(dp, bp);
        btp = xfs_dir2_block_tail_p(mp, hdr);
        blp = xfs_dir2_block_leaf_p(btp);
        /*
         * Get the offset from the leaf entry, to point to the data.
         */
        dep = (xfs_dir2_data_entry_t *)((char *)hdr +
                xfs_dir2_dataptr_to_off(mp, be32_to_cpu(blp[ent].address)));
        /*
         * Fill in inode number, CI name if appropriate, release the block.
         */
        args->inumber = be64_to_cpu(dep->inumber);
        error = xfs_dir_cilookup_result(args, dep->name, dep->namelen);
        xfs_trans_brelse(args->trans, bp);
        return XFS_ERROR(error);
}

/*
 * Internal block lookup routine.
 */
static int                                      /* error */
xfs_dir2_block_lookup_int(
        xfs_da_args_t           *args,          /* dir lookup arguments */
        struct xfs_buf          **bpp,          /* returned block buffer */
        int                     *entno)         /* returned entry number */
{
        xfs_dir2_dataptr_t      addr;           /* data entry address */
        xfs_dir2_data_hdr_t     *hdr;           /* block header */
        xfs_dir2_leaf_entry_t   *blp;           /* block leaf entries */
        struct xfs_buf          *bp;            /* block buffer */
        xfs_dir2_block_tail_t   *btp;           /* block tail */
        xfs_dir2_data_entry_t   *dep;           /* block data entry */
        xfs_inode_t             *dp;            /* incore inode */
        int                     error;          /* error return value */
        xfs_dahash_t            hash;           /* found hash value */
        int                     high;           /* binary search high index */
        int                     low;            /* binary search low index */
        int                     mid;            /* binary search current idx */
        xfs_mount_t             *mp;            /* filesystem mount point */
        xfs_trans_t             *tp;            /* transaction pointer */
        enum xfs_dacmp          cmp;            /* comparison result */

        dp = args->dp;
        tp = args->trans;
        mp = dp->i_mount;

        error = xfs_dir2_block_read(tp, dp, &bp);
        if (error)
                return error;

        hdr = bp->b_addr;
        xfs_dir2_data_check(dp, bp);
        btp = xfs_dir2_block_tail_p(mp, hdr);
        blp = xfs_dir2_block_leaf_p(btp);
        /*
         * Loop doing a binary search for our hash value.
         * Find our entry, ENOENT if it's not there.
         */
        for (low = 0, high = be32_to_cpu(btp->count) - 1; ; ) {
                ASSERT(low <= high);
                mid = (low + high) >> 1;
                if ((hash = be32_to_cpu(blp[mid].hashval)) == args->hashval)
                        break;
                if (hash < args->hashval)
                        low = mid + 1;
                else
                        high = mid - 1;
                if (low > high) {
                        ASSERT(args->op_flags & XFS_DA_OP_OKNOENT);
                        xfs_trans_brelse(tp, bp);
                        return XFS_ERROR(ENOENT);
                }
        }
        /*
         * Back up to the first one with the right hash value.
         */
        while (mid > 0 && be32_to_cpu(blp[mid - 1].hashval) == args->hashval) {
                mid--;
        }
        /*
         * Now loop forward through all the entries with the
         * right hash value looking for our name.
         */
        do {
                if ((addr = be32_to_cpu(blp[mid].address)) == XFS_DIR2_NULL_DATAPTR)
                        continue;
                /*
                 * Get pointer to the entry from the leaf.
                 */
                dep = (xfs_dir2_data_entry_t *)
                        ((char *)hdr + xfs_dir2_dataptr_to_off(mp, addr));
                /*
                 * Compare name and if it's an exact match, return the index
                 * and buffer. If it's the first case-insensitive match, store
                 * the index and buffer and continue looking for an exact match.
                 */
                cmp = mp->m_dirnameops->compname(args, dep->name, dep->namelen);
                if (cmp != XFS_CMP_DIFFERENT && cmp != args->cmpresult) {
                        args->cmpresult = cmp;
                        *bpp = bp;
                        *entno = mid;
                        if (cmp == XFS_CMP_EXACT)
                                return 0;
                }
        } while (++mid < be32_to_cpu(btp->count) &&
                        be32_to_cpu(blp[mid].hashval) == hash);

        ASSERT(args->op_flags & XFS_DA_OP_OKNOENT);
        /*
         * Here, we can only be doing a lookup (not a rename or replace).
         * If a case-insensitive match was found earlier, return success.
         */
        if (args->cmpresult == XFS_CMP_CASE)
                return 0;
        /*
         * No match, release the buffer and return ENOENT.
         */
        xfs_trans_brelse(tp, bp);
        return XFS_ERROR(ENOENT);
}

/*
 * Remove an entry from a block format directory.
 * If that makes the block small enough to fit in shortform, transform it.
 */
int                                             /* error */
xfs_dir2_block_removename(
        xfs_da_args_t           *args)          /* directory operation args */
{
        xfs_dir2_data_hdr_t     *hdr;           /* block header */
        xfs_dir2_leaf_entry_t   *blp;           /* block leaf pointer */
        struct xfs_buf          *bp;            /* block buffer */
        xfs_dir2_block_tail_t   *btp;           /* block tail */
        xfs_dir2_data_entry_t   *dep;           /* block data entry */
        xfs_inode_t             *dp;            /* incore inode */
        int                     ent;            /* block leaf entry index */
        int                     error;          /* error return value */
        xfs_mount_t             *mp;            /* filesystem mount point */
        int                     needlog;        /* need to log block header */
        int                     needscan;       /* need to fixup bestfree */
        xfs_dir2_sf_hdr_t       sfh;            /* shortform header */
        int                     size;           /* shortform size */
        xfs_trans_t             *tp;            /* transaction pointer */

        trace_xfs_dir2_block_removename(args);

        /*
         * Look up the entry in the block.  Gets the buffer and entry index.
         * It will always be there, the vnodeops level does a lookup first.
         */
        if ((error = xfs_dir2_block_lookup_int(args, &bp, &ent))) {
                return error;
        }
        dp = args->dp;
        tp = args->trans;
        mp = dp->i_mount;
        hdr = bp->b_addr;
        btp = xfs_dir2_block_tail_p(mp, hdr);
        blp = xfs_dir2_block_leaf_p(btp);
        /*
         * Point to the data entry using the leaf entry.
         */
        dep = (xfs_dir2_data_entry_t *)
              ((char *)hdr + xfs_dir2_dataptr_to_off(mp, be32_to_cpu(blp[ent].address)));
        /*
         * Mark the data entry's space free.
         */
        needlog = needscan = 0;
        xfs_dir2_data_make_free(tp, bp,
                (xfs_dir2_data_aoff_t)((char *)dep - (char *)hdr),
                xfs_dir2_data_entsize(dep->namelen), &needlog, &needscan);
        /*
         * Fix up the block tail.
         */
        be32_add_cpu(&btp->stale, 1);
        xfs_dir2_block_log_tail(tp, bp);
        /*
         * Remove the leaf entry by marking it stale.
         */
        blp[ent].address = cpu_to_be32(XFS_DIR2_NULL_DATAPTR);
        xfs_dir2_block_log_leaf(tp, bp, ent, ent);
        /*
         * Fix up bestfree, log the header if necessary.
         */
        if (needscan)
                xfs_dir2_data_freescan(mp, hdr, &needlog);
        if (needlog)
                xfs_dir2_data_log_header(tp, bp);
        xfs_dir2_data_check(dp, bp);
        /*
         * See if the size as a shortform is good enough.
         */
        size = xfs_dir2_block_sfsize(dp, hdr, &sfh);
        if (size > XFS_IFORK_DSIZE(dp))
                return 0;

        /*
         * If it works, do the conversion.
         */
        return xfs_dir2_block_to_sf(args, bp, size, &sfh);
}

/*
 * Replace an entry in a V2 block directory.
 * Change the inode number to the new value.
 */
int                                             /* error */
xfs_dir2_block_replace(
        xfs_da_args_t           *args)          /* directory operation args */
{
        xfs_dir2_data_hdr_t     *hdr;           /* block header */
        xfs_dir2_leaf_entry_t   *blp;           /* block leaf entries */
        struct xfs_buf          *bp;            /* block buffer */
        xfs_dir2_block_tail_t   *btp;           /* block tail */
        xfs_dir2_data_entry_t   *dep;           /* block data entry */
        xfs_inode_t             *dp;            /* incore inode */
        int                     ent;            /* leaf entry index */
        int                     error;          /* error return value */
        xfs_mount_t             *mp;            /* filesystem mount point */

        trace_xfs_dir2_block_replace(args);

        /*
         * Lookup the entry in the directory.  Get buffer and entry index.
         * This will always succeed since the caller has already done a lookup.
         */
        if ((error = xfs_dir2_block_lookup_int(args, &bp, &ent))) {
                return error;
        }
        dp = args->dp;
        mp = dp->i_mount;
        hdr = bp->b_addr;
        btp = xfs_dir2_block_tail_p(mp, hdr);
        blp = xfs_dir2_block_leaf_p(btp);
        /*
         * Point to the data entry we need to change.
         */
        dep = (xfs_dir2_data_entry_t *)
              ((char *)hdr + xfs_dir2_dataptr_to_off(mp, be32_to_cpu(blp[ent].address)));
        ASSERT(be64_to_cpu(dep->inumber) != args->inumber);
        /*
         * Change the inode number to the new value.
         */
        dep->inumber = cpu_to_be64(args->inumber);
        xfs_dir2_data_log_entry(args->trans, bp, dep);
        xfs_dir2_data_check(dp, bp);
        return 0;
}

/*
 * Qsort comparison routine for the block leaf entries.
 */
static int                                      /* sort order */
xfs_dir2_block_sort(
        const void                      *a,     /* first leaf entry */
        const void                      *b)     /* second leaf entry */
{
        const xfs_dir2_leaf_entry_t     *la;    /* first leaf entry */
        const xfs_dir2_leaf_entry_t     *lb;    /* second leaf entry */

        la = a;
        lb = b;
        return be32_to_cpu(la->hashval) < be32_to_cpu(lb->hashval) ? -1 :
                (be32_to_cpu(la->hashval) > be32_to_cpu(lb->hashval) ? 1 : 0);
}

/*
 * Convert a V2 leaf directory to a V2 block directory if possible.
 */
int                                             /* error */
xfs_dir2_leaf_to_block(
        xfs_da_args_t           *args,          /* operation arguments */
        struct xfs_buf          *lbp,           /* leaf buffer */
        struct xfs_buf          *dbp)           /* data buffer */
{
        __be16                  *bestsp;        /* leaf bests table */
        xfs_dir2_data_hdr_t     *hdr;           /* block header */
        xfs_dir2_block_tail_t   *btp;           /* block tail */
        xfs_inode_t             *dp;            /* incore directory inode */
        xfs_dir2_data_unused_t  *dup;           /* unused data entry */
        int                     error;          /* error return value */
        int                     from;           /* leaf from index */
        xfs_dir2_leaf_t         *leaf;          /* leaf structure */
        xfs_dir2_leaf_entry_t   *lep;           /* leaf entry */
        xfs_dir2_leaf_tail_t    *ltp;           /* leaf tail structure */
        xfs_mount_t             *mp;            /* file system mount point */
        int                     needlog;        /* need to log data header */
        int                     needscan;       /* need to scan for bestfree */
        xfs_dir2_sf_hdr_t       sfh;            /* shortform header */
        int                     size;           /* bytes used */
        __be16                  *tagp;          /* end of entry (tag) */
        int                     to;             /* block/leaf to index */
        xfs_trans_t             *tp;            /* transaction pointer */

        trace_xfs_dir2_leaf_to_block(args);

        dp = args->dp;
        tp = args->trans;
        mp = dp->i_mount;
        leaf = lbp->b_addr;
        ASSERT(leaf->hdr.info.magic == cpu_to_be16(XFS_DIR2_LEAF1_MAGIC));
        ltp = xfs_dir2_leaf_tail_p(mp, leaf);
        /*
         * If there are data blocks other than the first one, take this
         * opportunity to remove trailing empty data blocks that may have
         * been left behind during no-space-reservation operations.
         * These will show up in the leaf bests table.
         */
        while (dp->i_d.di_size > mp->m_dirblksize) {
                bestsp = xfs_dir2_leaf_bests_p(ltp);
                if (be16_to_cpu(bestsp[be32_to_cpu(ltp->bestcount) - 1]) ==
                    mp->m_dirblksize - (uint)sizeof(*hdr)) {
                        if ((error =
                            xfs_dir2_leaf_trim_data(args, lbp,
                                    (xfs_dir2_db_t)(be32_to_cpu(ltp->bestcount) - 1))))
                                return error;
                } else
                        return 0;
        }
        /*
         * Read the data block if we don't already have it, give up if it fails.
         */
        if (!dbp) {
                error = xfs_dir2_data_read(tp, dp, mp->m_dirdatablk, -1, &dbp);
                if (error)
                        return error;
        }
        hdr = dbp->b_addr;
        ASSERT(hdr->magic == cpu_to_be32(XFS_DIR2_DATA_MAGIC));
        /*
         * Size of the "leaf" area in the block.
         */
        size = (uint)sizeof(xfs_dir2_block_tail_t) +
               (uint)sizeof(*lep) * (be16_to_cpu(leaf->hdr.count) - be16_to_cpu(leaf->hdr.stale));
        /*
         * Look at the last data entry.
         */
        tagp = (__be16 *)((char *)hdr + mp->m_dirblksize) - 1;
        dup = (xfs_dir2_data_unused_t *)((char *)hdr + be16_to_cpu(*tagp));
        /*
         * If it's not free or is too short we can't do it.
         */
        if (be16_to_cpu(dup->freetag) != XFS_DIR2_DATA_FREE_TAG ||
            be16_to_cpu(dup->length) < size)
                return 0;

        /*
         * Start converting it to block form.
         */
        dbp->b_ops = &xfs_dir2_block_buf_ops;
        hdr->magic = cpu_to_be32(XFS_DIR2_BLOCK_MAGIC);
        needlog = 1;
        needscan = 0;
        /*
         * Use up the space at the end of the block (blp/btp).
         */
        xfs_dir2_data_use_free(tp, dbp, dup, mp->m_dirblksize - size, size,
                &needlog, &needscan);
        /*
         * Initialize the block tail.
         */
        btp = xfs_dir2_block_tail_p(mp, hdr);
        btp->count = cpu_to_be32(be16_to_cpu(leaf->hdr.count) - be16_to_cpu(leaf->hdr.stale));
        btp->stale = 0;
        xfs_dir2_block_log_tail(tp, dbp);
        /*
         * Initialize the block leaf area.  We compact out stale entries.
         */
        lep = xfs_dir2_block_leaf_p(btp);
        for (from = to = 0; from < be16_to_cpu(leaf->hdr.count); from++) {
                if (leaf->ents[from].address ==
                    cpu_to_be32(XFS_DIR2_NULL_DATAPTR))
                        continue;
                lep[to++] = leaf->ents[from];
        }
        ASSERT(to == be32_to_cpu(btp->count));
        xfs_dir2_block_log_leaf(tp, dbp, 0, be32_to_cpu(btp->count) - 1);
        /*
         * Scan the bestfree if we need it and log the data block header.
         */
        if (needscan)
                xfs_dir2_data_freescan(mp, hdr, &needlog);
        if (needlog)
                xfs_dir2_data_log_header(tp, dbp);
        /*
         * Pitch the old leaf block.
         */
        error = xfs_da_shrink_inode(args, mp->m_dirleafblk, lbp);
        if (error)
                return error;

        /*
         * Now see if the resulting block can be shrunken to shortform.
         */
        size = xfs_dir2_block_sfsize(dp, hdr, &sfh);
        if (size > XFS_IFORK_DSIZE(dp))
                return 0;

        return xfs_dir2_block_to_sf(args, dbp, size, &sfh);
}

/*
 * Convert the shortform directory to block form.
 */
int                                             /* error */
xfs_dir2_sf_to_block(
        xfs_da_args_t           *args)          /* operation arguments */
{
        xfs_dir2_db_t           blkno;          /* dir-relative block # (0) */
        xfs_dir2_data_hdr_t     *hdr;           /* block header */
        xfs_dir2_leaf_entry_t   *blp;           /* block leaf entries */
        struct xfs_buf          *bp;            /* block buffer */
        xfs_dir2_block_tail_t   *btp;           /* block tail pointer */
        xfs_dir2_data_entry_t   *dep;           /* data entry pointer */
        xfs_inode_t             *dp;            /* incore directory inode */
        int                     dummy;          /* trash */
        xfs_dir2_data_unused_t  *dup;           /* unused entry pointer */
        int                     endoffset;      /* end of data objects */
        int                     error;          /* error return value */
        int                     i;              /* index */
        xfs_mount_t             *mp;            /* filesystem mount point */
        int                     needlog;        /* need to log block header */
        int                     needscan;       /* need to scan block freespc */
        int                     newoffset;      /* offset from current entry */
        int                     offset;         /* target block offset */
        xfs_dir2_sf_entry_t     *sfep;          /* sf entry pointer */
        xfs_dir2_sf_hdr_t       *oldsfp;        /* old shortform header  */
        xfs_dir2_sf_hdr_t       *sfp;           /* shortform header  */
        __be16                  *tagp;          /* end of data entry */
        xfs_trans_t             *tp;            /* transaction pointer */
        struct xfs_name         name;

        trace_xfs_dir2_sf_to_block(args);

        dp = args->dp;
        tp = args->trans;
        mp = dp->i_mount;
        ASSERT(dp->i_df.if_flags & XFS_IFINLINE);
        /*
         * Bomb out if the shortform directory is way too short.
         */
        if (dp->i_d.di_size < offsetof(xfs_dir2_sf_hdr_t, parent)) {
                ASSERT(XFS_FORCED_SHUTDOWN(mp));
                return XFS_ERROR(EIO);
        }

        oldsfp = (xfs_dir2_sf_hdr_t *)dp->i_df.if_u1.if_data;

        ASSERT(dp->i_df.if_bytes == dp->i_d.di_size);
        ASSERT(dp->i_df.if_u1.if_data != NULL);
        ASSERT(dp->i_d.di_size >= xfs_dir2_sf_hdr_size(oldsfp->i8count));

        /*
         * Copy the directory into a temporary buffer.
         * Then pitch the incore inode data so we can make extents.
         */
        sfp = kmem_alloc(dp->i_df.if_bytes, KM_SLEEP);
        memcpy(sfp, oldsfp, dp->i_df.if_bytes);

        xfs_idata_realloc(dp, -dp->i_df.if_bytes, XFS_DATA_FORK);
        dp->i_d.di_size = 0;
        xfs_trans_log_inode(tp, dp, XFS_ILOG_CORE);

        /*
         * Add block 0 to the inode.
         */
        error = xfs_dir2_grow_inode(args, XFS_DIR2_DATA_SPACE, &blkno);
        if (error) {
                kmem_free(sfp);
                return error;
        }
        /*
         * Initialize the data block.
         */
        error = xfs_dir2_data_init(args, blkno, &bp);
        if (error) {
                kmem_free(sfp);
                return error;
        }
        bp->b_ops = &xfs_dir2_block_buf_ops;
        hdr = bp->b_addr;
        hdr->magic = cpu_to_be32(XFS_DIR2_BLOCK_MAGIC);
        /*
         * Compute size of block "tail" area.
         */
        i = (uint)sizeof(*btp) +
            (sfp->count + 2) * (uint)sizeof(xfs_dir2_leaf_entry_t);
        /*
         * The whole thing is initialized to free by the init routine.
         * Say we're using the leaf and tail area.
         */
        dup = (xfs_dir2_data_unused_t *)(hdr + 1);
        needlog = needscan = 0;
        xfs_dir2_data_use_free(tp, bp, dup, mp->m_dirblksize - i, i, &needlog,
                &needscan);
        ASSERT(needscan == 0);
        /*
         * Fill in the tail.
         */
        btp = xfs_dir2_block_tail_p(mp, hdr);
        btp->count = cpu_to_be32(sfp->count + 2);       /* ., .. */
        btp->stale = 0;
        blp = xfs_dir2_block_leaf_p(btp);
        endoffset = (uint)((char *)blp - (char *)hdr);
        /*
         * Remove the freespace, we'll manage it.
         */
        xfs_dir2_data_use_free(tp, bp, dup,
                (xfs_dir2_data_aoff_t)((char *)dup - (char *)hdr),
                be16_to_cpu(dup->length), &needlog, &needscan);
        /*
         * Create entry for .
         */
        dep = (xfs_dir2_data_entry_t *)
              ((char *)hdr + XFS_DIR2_DATA_DOT_OFFSET);
        dep->inumber = cpu_to_be64(dp->i_ino);
        dep->namelen = 1;
        dep->name[0] = '.';
        tagp = xfs_dir2_data_entry_tag_p(dep);
        *tagp = cpu_to_be16((char *)dep - (char *)hdr);
        xfs_dir2_data_log_entry(tp, bp, dep);
        blp[0].hashval = cpu_to_be32(xfs_dir_hash_dot);
        blp[0].address = cpu_to_be32(xfs_dir2_byte_to_dataptr(mp,
                                (char *)dep - (char *)hdr));
        /*
         * Create entry for ..
         */
        dep = (xfs_dir2_data_entry_t *)
                ((char *)hdr + XFS_DIR2_DATA_DOTDOT_OFFSET);
        dep->inumber = cpu_to_be64(xfs_dir2_sf_get_parent_ino(sfp));
        dep->namelen = 2;
        dep->name[0] = dep->name[1] = '.';
        tagp = xfs_dir2_data_entry_tag_p(dep);
        *tagp = cpu_to_be16((char *)dep - (char *)hdr);
        xfs_dir2_data_log_entry(tp, bp, dep);
        blp[1].hashval = cpu_to_be32(xfs_dir_hash_dotdot);
        blp[1].address = cpu_to_be32(xfs_dir2_byte_to_dataptr(mp,
                                (char *)dep - (char *)hdr));
        offset = XFS_DIR2_DATA_FIRST_OFFSET;
        /*
         * Loop over existing entries, stuff them in.
         */
        i = 0;
        if (!sfp->count)
                sfep = NULL;
        else
                sfep = xfs_dir2_sf_firstentry(sfp);
        /*
         * Need to preserve the existing offset values in the sf directory.
         * Insert holes (unused entries) where necessary.
         */
        while (offset < endoffset) {
                /*
                 * sfep is null when we reach the end of the list.
                 */
                if (sfep == NULL)
                        newoffset = endoffset;
                else
                        newoffset = xfs_dir2_sf_get_offset(sfep);
                /*
                 * There should be a hole here, make one.
                 */
                if (offset < newoffset) {
                        dup = (xfs_dir2_data_unused_t *)((char *)hdr + offset);
                        dup->freetag = cpu_to_be16(XFS_DIR2_DATA_FREE_TAG);
                        dup->length = cpu_to_be16(newoffset - offset);
                        *xfs_dir2_data_unused_tag_p(dup) = cpu_to_be16(
                                ((char *)dup - (char *)hdr));
                        xfs_dir2_data_log_unused(tp, bp, dup);
                        xfs_dir2_data_freeinsert(hdr, dup, &dummy);
                        offset += be16_to_cpu(dup->length);
                        continue;
                }
                /*
                 * Copy a real entry.
                 */
                dep = (xfs_dir2_data_entry_t *)((char *)hdr + newoffset);
                dep->inumber = cpu_to_be64(xfs_dir2_sfe_get_ino(sfp, sfep));
                dep->namelen = sfep->namelen;
                memcpy(dep->name, sfep->name, dep->namelen);
                tagp = xfs_dir2_data_entry_tag_p(dep);
                *tagp = cpu_to_be16((char *)dep - (char *)hdr);
                xfs_dir2_data_log_entry(tp, bp, dep);
                name.name = sfep->name;
                name.len = sfep->namelen;
                blp[2 + i].hashval = cpu_to_be32(mp->m_dirnameops->
                                                        hashname(&name));
                blp[2 + i].address = cpu_to_be32(xfs_dir2_byte_to_dataptr(mp,
                                                 (char *)dep - (char *)hdr));
                offset = (int)((char *)(tagp + 1) - (char *)hdr);
                if (++i == sfp->count)
                        sfep = NULL;
                else
                        sfep = xfs_dir2_sf_nextentry(sfp, sfep);
        }
        /* Done with the temporary buffer */
        kmem_free(sfp);
        /*
         * Sort the leaf entries by hash value.
         */
        xfs_sort(blp, be32_to_cpu(btp->count), sizeof(*blp), xfs_dir2_block_sort);
        /*
         * Log the leaf entry area and tail.
         * Already logged the header in data_init, ignore needlog.
         */
        ASSERT(needscan == 0);
        xfs_dir2_block_log_leaf(tp, bp, 0, be32_to_cpu(btp->count) - 1);
        xfs_dir2_block_log_tail(tp, bp);
        xfs_dir2_data_check(dp, bp);
        return 0;
}