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[pv_ops_mirror.git] / fs / xfs / xfs_alloc_btree.c

/*
 * Copyright (c) 2000-2001,2005 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_bit.h"
#include "xfs_log.h"
#include "xfs_inum.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_dir2.h"
#include "xfs_dmapi.h"
#include "xfs_mount.h"
#include "xfs_bmap_btree.h"
#include "xfs_alloc_btree.h"
#include "xfs_ialloc_btree.h"
#include "xfs_dir2_sf.h"
#include "xfs_attr_sf.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_btree.h"
#include "xfs_ialloc.h"
#include "xfs_alloc.h"
#include "xfs_error.h"

/*
 * Prototypes for internal functions.
 */

STATIC void xfs_alloc_log_block(xfs_trans_t *, xfs_buf_t *, int);
STATIC void xfs_alloc_log_keys(xfs_btree_cur_t *, xfs_buf_t *, int, int);
STATIC void xfs_alloc_log_ptrs(xfs_btree_cur_t *, xfs_buf_t *, int, int);
STATIC void xfs_alloc_log_recs(xfs_btree_cur_t *, xfs_buf_t *, int, int);
STATIC int xfs_alloc_lshift(xfs_btree_cur_t *, int, int *);
STATIC int xfs_alloc_newroot(xfs_btree_cur_t *, int *);
STATIC int xfs_alloc_rshift(xfs_btree_cur_t *, int, int *);
STATIC int xfs_alloc_split(xfs_btree_cur_t *, int, xfs_agblock_t *,
                xfs_alloc_key_t *, xfs_btree_cur_t **, int *);
STATIC int xfs_alloc_updkey(xfs_btree_cur_t *, xfs_alloc_key_t *, int);

/*
 * Internal functions.
 */

/*
 * Single level of the xfs_alloc_delete record deletion routine.
 * Delete record pointed to by cur/level.
 * Remove the record from its block then rebalance the tree.
 * Return 0 for error, 1 for done, 2 to go on to the next level.
 */
STATIC int                              /* error */
xfs_alloc_delrec(
        xfs_btree_cur_t         *cur,   /* btree cursor */
        int                     level,  /* level removing record from */
        int                     *stat)  /* fail/done/go-on */
{
        xfs_agf_t               *agf;   /* allocation group freelist header */
        xfs_alloc_block_t       *block; /* btree block record/key lives in */
        xfs_agblock_t           bno;    /* btree block number */
        xfs_buf_t               *bp;    /* buffer for block */
        int                     error;  /* error return value */
        int                     i;      /* loop index */
        xfs_alloc_key_t         key;    /* kp points here if block is level 0 */
        xfs_agblock_t           lbno;   /* left block's block number */
        xfs_buf_t               *lbp;   /* left block's buffer pointer */
        xfs_alloc_block_t       *left;  /* left btree block */
        xfs_alloc_key_t         *lkp=NULL;      /* left block key pointer */
        xfs_alloc_ptr_t         *lpp=NULL;      /* left block address pointer */
        int                     lrecs=0;        /* number of records in left block */
        xfs_alloc_rec_t         *lrp;   /* left block record pointer */
        xfs_mount_t             *mp;    /* mount structure */
        int                     ptr;    /* index in btree block for this rec */
        xfs_agblock_t           rbno;   /* right block's block number */
        xfs_buf_t               *rbp;   /* right block's buffer pointer */
        xfs_alloc_block_t       *right; /* right btree block */
        xfs_alloc_key_t         *rkp;   /* right block key pointer */
        xfs_alloc_ptr_t         *rpp;   /* right block address pointer */
        int                     rrecs=0;        /* number of records in right block */
        int                     numrecs;
        xfs_alloc_rec_t         *rrp;   /* right block record pointer */
        xfs_btree_cur_t         *tcur;  /* temporary btree cursor */

        /*
         * Get the index of the entry being deleted, check for nothing there.
         */
        ptr = cur->bc_ptrs[level];
        if (ptr == 0) {
                *stat = 0;
                return 0;
        }
        /*
         * Get the buffer & block containing the record or key/ptr.
         */
        bp = cur->bc_bufs[level];
        block = XFS_BUF_TO_ALLOC_BLOCK(bp);
#ifdef DEBUG
        if ((error = xfs_btree_check_sblock(cur, block, level, bp)))
                return error;
#endif
        /*
         * Fail if we're off the end of the block.
         */
        numrecs = be16_to_cpu(block->bb_numrecs);
        if (ptr > numrecs) {
                *stat = 0;
                return 0;
        }
        XFS_STATS_INC(xs_abt_delrec);
        /*
         * It's a nonleaf.  Excise the key and ptr being deleted, by
         * sliding the entries past them down one.
         * Log the changed areas of the block.
         */
        if (level > 0) {
                lkp = XFS_ALLOC_KEY_ADDR(block, 1, cur);
                lpp = XFS_ALLOC_PTR_ADDR(block, 1, cur);
#ifdef DEBUG
                for (i = ptr; i < numrecs; i++) {
                        if ((error = xfs_btree_check_sptr(cur, be32_to_cpu(lpp[i]), level)))
                                return error;
                }
#endif
                if (ptr < numrecs) {
                        memmove(&lkp[ptr - 1], &lkp[ptr],
                                (numrecs - ptr) * sizeof(*lkp));
                        memmove(&lpp[ptr - 1], &lpp[ptr],
                                (numrecs - ptr) * sizeof(*lpp));
                        xfs_alloc_log_ptrs(cur, bp, ptr, numrecs - 1);
                        xfs_alloc_log_keys(cur, bp, ptr, numrecs - 1);
                }
        }
        /*
         * It's a leaf.  Excise the record being deleted, by sliding the
         * entries past it down one.  Log the changed areas of the block.
         */
        else {
                lrp = XFS_ALLOC_REC_ADDR(block, 1, cur);
                if (ptr < numrecs) {
                        memmove(&lrp[ptr - 1], &lrp[ptr],
                                (numrecs - ptr) * sizeof(*lrp));
                        xfs_alloc_log_recs(cur, bp, ptr, numrecs - 1);
                }
                /*
                 * If it's the first record in the block, we'll need a key
                 * structure to pass up to the next level (updkey).
                 */
                if (ptr == 1) {
                        key.ar_startblock = lrp->ar_startblock;
                        key.ar_blockcount = lrp->ar_blockcount;
                        lkp = &key;
                }
        }
        /*
         * Decrement and log the number of entries in the block.
         */
        numrecs--;
        block->bb_numrecs = cpu_to_be16(numrecs);
        xfs_alloc_log_block(cur->bc_tp, bp, XFS_BB_NUMRECS);
        /*
         * See if the longest free extent in the allocation group was
         * changed by this operation.  True if it's the by-size btree, and
         * this is the leaf level, and there is no right sibling block,
         * and this was the last record.
         */
        agf = XFS_BUF_TO_AGF(cur->bc_private.a.agbp);
        mp = cur->bc_mp;

        if (level == 0 &&
            cur->bc_btnum == XFS_BTNUM_CNT &&
            be32_to_cpu(block->bb_rightsib) == NULLAGBLOCK &&
            ptr > numrecs) {
                ASSERT(ptr == numrecs + 1);
                /*
                 * There are still records in the block.  Grab the size
                 * from the last one.
                 */
                if (numrecs) {
                        rrp = XFS_ALLOC_REC_ADDR(block, numrecs, cur);
                        agf->agf_longest = rrp->ar_blockcount;
                }
                /*
                 * No free extents left.
                 */
                else
                        agf->agf_longest = 0;
                mp->m_perag[be32_to_cpu(agf->agf_seqno)].pagf_longest =
                        be32_to_cpu(agf->agf_longest);
                xfs_alloc_log_agf(cur->bc_tp, cur->bc_private.a.agbp,
                        XFS_AGF_LONGEST);
        }
        /*
         * Is this the root level?  If so, we're almost done.
         */
        if (level == cur->bc_nlevels - 1) {
                /*
                 * If this is the root level,
                 * and there's only one entry left,
                 * and it's NOT the leaf level,
                 * then we can get rid of this level.
                 */
                if (numrecs == 1 && level > 0) {
                        /*
                         * lpp is still set to the first pointer in the block.
                         * Make it the new root of the btree.
                         */
                        bno = be32_to_cpu(agf->agf_roots[cur->bc_btnum]);
                        agf->agf_roots[cur->bc_btnum] = *lpp;
                        be32_add(&agf->agf_levels[cur->bc_btnum], -1);
                        mp->m_perag[be32_to_cpu(agf->agf_seqno)].pagf_levels[cur->bc_btnum]--;
                        /*
                         * Put this buffer/block on the ag's freelist.
                         */
                        if ((error = xfs_alloc_put_freelist(cur->bc_tp,
                                        cur->bc_private.a.agbp, NULL, bno)))
                                return error;
                        /*
                         * Since blocks move to the free list without the
                         * coordination used in xfs_bmap_finish, we can't allow
                         * block to be available for reallocation and
                         * non-transaction writing (user data) until we know
                         * that the transaction that moved it to the free list
                         * is permanently on disk. We track the blocks by
                         * declaring these blocks as "busy"; the busy list is
                         * maintained on a per-ag basis and each transaction
                         * records which entries should be removed when the
                         * iclog commits to disk. If a busy block is
                         * allocated, the iclog is pushed up to the LSN
                         * that freed the block.
                         */
                        xfs_alloc_mark_busy(cur->bc_tp,
                                be32_to_cpu(agf->agf_seqno), bno, 1);

                        xfs_trans_agbtree_delta(cur->bc_tp, -1);
                        xfs_alloc_log_agf(cur->bc_tp, cur->bc_private.a.agbp,
                                XFS_AGF_ROOTS | XFS_AGF_LEVELS);
                        /*
                         * Update the cursor so there's one fewer level.
                         */
                        xfs_btree_setbuf(cur, level, NULL);
                        cur->bc_nlevels--;
                } else if (level > 0 &&
                           (error = xfs_alloc_decrement(cur, level, &i)))
                        return error;
                *stat = 1;
                return 0;
        }
        /*
         * If we deleted the leftmost entry in the block, update the
         * key values above us in the tree.
         */
        if (ptr == 1 && (error = xfs_alloc_updkey(cur, lkp, level + 1)))
                return error;
        /*
         * If the number of records remaining in the block is at least
         * the minimum, we're done.
         */
        if (numrecs >= XFS_ALLOC_BLOCK_MINRECS(level, cur)) {
                if (level > 0 && (error = xfs_alloc_decrement(cur, level, &i)))
                        return error;
                *stat = 1;
                return 0;
        }
        /*
         * Otherwise, we have to move some records around to keep the
         * tree balanced.  Look at the left and right sibling blocks to
         * see if we can re-balance by moving only one record.
         */
        rbno = be32_to_cpu(block->bb_rightsib);
        lbno = be32_to_cpu(block->bb_leftsib);
        bno = NULLAGBLOCK;
        ASSERT(rbno != NULLAGBLOCK || lbno != NULLAGBLOCK);
        /*
         * Duplicate the cursor so our btree manipulations here won't
         * disrupt the next level up.
         */
        if ((error = xfs_btree_dup_cursor(cur, &tcur)))
                return error;
        /*
         * If there's a right sibling, see if it's ok to shift an entry
         * out of it.
         */
        if (rbno != NULLAGBLOCK) {
                /*
                 * Move the temp cursor to the last entry in the next block.
                 * Actually any entry but the first would suffice.
                 */
                i = xfs_btree_lastrec(tcur, level);
                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                if ((error = xfs_alloc_increment(tcur, level, &i)))
                        goto error0;
                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                i = xfs_btree_lastrec(tcur, level);
                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                /*
                 * Grab a pointer to the block.
                 */
                rbp = tcur->bc_bufs[level];
                right = XFS_BUF_TO_ALLOC_BLOCK(rbp);
#ifdef DEBUG
                if ((error = xfs_btree_check_sblock(cur, right, level, rbp)))
                        goto error0;
#endif
                /*
                 * Grab the current block number, for future use.
                 */
                bno = be32_to_cpu(right->bb_leftsib);
                /*
                 * If right block is full enough so that removing one entry
                 * won't make it too empty, and left-shifting an entry out
                 * of right to us works, we're done.
                 */
                if (be16_to_cpu(right->bb_numrecs) - 1 >=
                     XFS_ALLOC_BLOCK_MINRECS(level, cur)) {
                        if ((error = xfs_alloc_lshift(tcur, level, &i)))
                                goto error0;
                        if (i) {
                                ASSERT(be16_to_cpu(block->bb_numrecs) >=
                                       XFS_ALLOC_BLOCK_MINRECS(level, cur));
                                xfs_btree_del_cursor(tcur,
                                                     XFS_BTREE_NOERROR);
                                if (level > 0 &&
                                    (error = xfs_alloc_decrement(cur, level,
                                            &i)))
                                        return error;
                                *stat = 1;
                                return 0;
                        }
                }
                /*
                 * Otherwise, grab the number of records in right for
                 * future reference, and fix up the temp cursor to point
                 * to our block again (last record).
                 */
                rrecs = be16_to_cpu(right->bb_numrecs);
                if (lbno != NULLAGBLOCK) {
                        i = xfs_btree_firstrec(tcur, level);
                        XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                        if ((error = xfs_alloc_decrement(tcur, level, &i)))
                                goto error0;
                        XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                }
        }
        /*
         * If there's a left sibling, see if it's ok to shift an entry
         * out of it.
         */
        if (lbno != NULLAGBLOCK) {
                /*
                 * Move the temp cursor to the first entry in the
                 * previous block.
                 */
                i = xfs_btree_firstrec(tcur, level);
                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                if ((error = xfs_alloc_decrement(tcur, level, &i)))
                        goto error0;
                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                xfs_btree_firstrec(tcur, level);
                /*
                 * Grab a pointer to the block.
                 */
                lbp = tcur->bc_bufs[level];
                left = XFS_BUF_TO_ALLOC_BLOCK(lbp);
#ifdef DEBUG
                if ((error = xfs_btree_check_sblock(cur, left, level, lbp)))
                        goto error0;
#endif
                /*
                 * Grab the current block number, for future use.
                 */
                bno = be32_to_cpu(left->bb_rightsib);
                /*
                 * If left block is full enough so that removing one entry
                 * won't make it too empty, and right-shifting an entry out
                 * of left to us works, we're done.
                 */
                if (be16_to_cpu(left->bb_numrecs) - 1 >=
                     XFS_ALLOC_BLOCK_MINRECS(level, cur)) {
                        if ((error = xfs_alloc_rshift(tcur, level, &i)))
                                goto error0;
                        if (i) {
                                ASSERT(be16_to_cpu(block->bb_numrecs) >=
                                       XFS_ALLOC_BLOCK_MINRECS(level, cur));
                                xfs_btree_del_cursor(tcur,
                                                     XFS_BTREE_NOERROR);
                                if (level == 0)
                                        cur->bc_ptrs[0]++;
                                *stat = 1;
                                return 0;
                        }
                }
                /*
                 * Otherwise, grab the number of records in right for
                 * future reference.
                 */
                lrecs = be16_to_cpu(left->bb_numrecs);
        }
        /*
         * Delete the temp cursor, we're done with it.
         */
        xfs_btree_del_cursor(tcur, XFS_BTREE_NOERROR);
        /*
         * If here, we need to do a join to keep the tree balanced.
         */
        ASSERT(bno != NULLAGBLOCK);
        /*
         * See if we can join with the left neighbor block.
         */
        if (lbno != NULLAGBLOCK &&
            lrecs + numrecs <= XFS_ALLOC_BLOCK_MAXRECS(level, cur)) {
                /*
                 * Set "right" to be the starting block,
                 * "left" to be the left neighbor.
                 */
                rbno = bno;
                right = block;
                rrecs = be16_to_cpu(right->bb_numrecs);
                rbp = bp;
                if ((error = xfs_btree_read_bufs(mp, cur->bc_tp,
                                cur->bc_private.a.agno, lbno, 0, &lbp,
                                XFS_ALLOC_BTREE_REF)))
                        return error;
                left = XFS_BUF_TO_ALLOC_BLOCK(lbp);
                lrecs = be16_to_cpu(left->bb_numrecs);
                if ((error = xfs_btree_check_sblock(cur, left, level, lbp)))
                        return error;
        }
        /*
         * If that won't work, see if we can join with the right neighbor block.
         */
        else if (rbno != NULLAGBLOCK &&
                 rrecs + numrecs <= XFS_ALLOC_BLOCK_MAXRECS(level, cur)) {
                /*
                 * Set "left" to be the starting block,
                 * "right" to be the right neighbor.
                 */
                lbno = bno;
                left = block;
                lrecs = be16_to_cpu(left->bb_numrecs);
                lbp = bp;
                if ((error = xfs_btree_read_bufs(mp, cur->bc_tp,
                                cur->bc_private.a.agno, rbno, 0, &rbp,
                                XFS_ALLOC_BTREE_REF)))
                        return error;
                right = XFS_BUF_TO_ALLOC_BLOCK(rbp);
                rrecs = be16_to_cpu(right->bb_numrecs);
                if ((error = xfs_btree_check_sblock(cur, right, level, rbp)))
                        return error;
        }
        /*
         * Otherwise, we can't fix the imbalance.
         * Just return.  This is probably a logic error, but it's not fatal.
         */
        else {
                if (level > 0 && (error = xfs_alloc_decrement(cur, level, &i)))
                        return error;
                *stat = 1;
                return 0;
        }
        /*
         * We're now going to join "left" and "right" by moving all the stuff
         * in "right" to "left" and deleting "right".
         */
        if (level > 0) {
                /*
                 * It's a non-leaf.  Move keys and pointers.
                 */
                lkp = XFS_ALLOC_KEY_ADDR(left, lrecs + 1, cur);
                lpp = XFS_ALLOC_PTR_ADDR(left, lrecs + 1, cur);
                rkp = XFS_ALLOC_KEY_ADDR(right, 1, cur);
                rpp = XFS_ALLOC_PTR_ADDR(right, 1, cur);
#ifdef DEBUG
                for (i = 0; i < rrecs; i++) {
                        if ((error = xfs_btree_check_sptr(cur, be32_to_cpu(rpp[i]), level)))
                                return error;
                }
#endif
                memcpy(lkp, rkp, rrecs * sizeof(*lkp));
                memcpy(lpp, rpp, rrecs * sizeof(*lpp));
                xfs_alloc_log_keys(cur, lbp, lrecs + 1, lrecs + rrecs);
                xfs_alloc_log_ptrs(cur, lbp, lrecs + 1, lrecs + rrecs);
        } else {
                /*
                 * It's a leaf.  Move records.
                 */
                lrp = XFS_ALLOC_REC_ADDR(left, lrecs + 1, cur);
                rrp = XFS_ALLOC_REC_ADDR(right, 1, cur);
                memcpy(lrp, rrp, rrecs * sizeof(*lrp));
                xfs_alloc_log_recs(cur, lbp, lrecs + 1, lrecs + rrecs);
        }
        /*
         * If we joined with the left neighbor, set the buffer in the
         * cursor to the left block, and fix up the index.
         */
        if (bp != lbp) {
                xfs_btree_setbuf(cur, level, lbp);
                cur->bc_ptrs[level] += lrecs;
        }
        /*
         * If we joined with the right neighbor and there's a level above
         * us, increment the cursor at that level.
         */
        else if (level + 1 < cur->bc_nlevels &&
                 (error = xfs_alloc_increment(cur, level + 1, &i)))
                return error;
        /*
         * Fix up the number of records in the surviving block.
         */
        lrecs += rrecs;
        left->bb_numrecs = cpu_to_be16(lrecs);
        /*
         * Fix up the right block pointer in the surviving block, and log it.
         */
        left->bb_rightsib = right->bb_rightsib;
        xfs_alloc_log_block(cur->bc_tp, lbp, XFS_BB_NUMRECS | XFS_BB_RIGHTSIB);
        /*
         * If there is a right sibling now, make it point to the
         * remaining block.
         */
        if (be32_to_cpu(left->bb_rightsib) != NULLAGBLOCK) {
                xfs_alloc_block_t       *rrblock;
                xfs_buf_t               *rrbp;

                if ((error = xfs_btree_read_bufs(mp, cur->bc_tp,
                                cur->bc_private.a.agno, be32_to_cpu(left->bb_rightsib), 0,
                                &rrbp, XFS_ALLOC_BTREE_REF)))
                        return error;
                rrblock = XFS_BUF_TO_ALLOC_BLOCK(rrbp);
                if ((error = xfs_btree_check_sblock(cur, rrblock, level, rrbp)))
                        return error;
                rrblock->bb_leftsib = cpu_to_be32(lbno);
                xfs_alloc_log_block(cur->bc_tp, rrbp, XFS_BB_LEFTSIB);
        }
        /*
         * Free the deleting block by putting it on the freelist.
         */
        if ((error = xfs_alloc_put_freelist(cur->bc_tp, cur->bc_private.a.agbp,
                        NULL, rbno)))
                return error;
        /*
         * Since blocks move to the free list without the coordination
         * used in xfs_bmap_finish, we can't allow block to be available
         * for reallocation and non-transaction writing (user data)
         * until we know that the transaction that moved it to the free
         * list is permanently on disk. We track the blocks by declaring
         * these blocks as "busy"; the busy list is maintained on a
         * per-ag basis and each transaction records which entries
         * should be removed when the iclog commits to disk. If a
         * busy block is allocated, the iclog is pushed up to the
         * LSN that freed the block.
         */
        xfs_alloc_mark_busy(cur->bc_tp, be32_to_cpu(agf->agf_seqno), bno, 1);
        xfs_trans_agbtree_delta(cur->bc_tp, -1);

        /*
         * Adjust the current level's cursor so that we're left referring
         * to the right node, after we're done.
         * If this leaves the ptr value 0 our caller will fix it up.
         */
        if (level > 0)
                cur->bc_ptrs[level]--;
        /*
         * Return value means the next level up has something to do.
         */
        *stat = 2;
        return 0;

error0:
        xfs_btree_del_cursor(tcur, XFS_BTREE_ERROR);
        return error;
}

/*
 * Insert one record/level.  Return information to the caller
 * allowing the next level up to proceed if necessary.
 */
STATIC int                              /* error */
xfs_alloc_insrec(
        xfs_btree_cur_t         *cur,   /* btree cursor */
        int                     level,  /* level to insert record at */
        xfs_agblock_t           *bnop,  /* i/o: block number inserted */
        xfs_alloc_rec_t         *recp,  /* i/o: record data inserted */
        xfs_btree_cur_t         **curp, /* output: new cursor replacing cur */
        int                     *stat)  /* output: success/failure */
{
        xfs_agf_t               *agf;   /* allocation group freelist header */
        xfs_alloc_block_t       *block; /* btree block record/key lives in */
        xfs_buf_t               *bp;    /* buffer for block */
        int                     error;  /* error return value */
        int                     i;      /* loop index */
        xfs_alloc_key_t         key;    /* key value being inserted */
        xfs_alloc_key_t         *kp;    /* pointer to btree keys */
        xfs_agblock_t           nbno;   /* block number of allocated block */
        xfs_btree_cur_t         *ncur;  /* new cursor to be used at next lvl */
        xfs_alloc_key_t         nkey;   /* new key value, from split */
        xfs_alloc_rec_t         nrec;   /* new record value, for caller */
        int                     numrecs;
        int                     optr;   /* old ptr value */
        xfs_alloc_ptr_t         *pp;    /* pointer to btree addresses */
        int                     ptr;    /* index in btree block for this rec */
        xfs_alloc_rec_t         *rp;    /* pointer to btree records */

        ASSERT(be32_to_cpu(recp->ar_blockcount) > 0);

        /*
         * GCC doesn't understand the (arguably complex) control flow in
         * this function and complains about uninitialized structure fields
         * without this.
         */
        memset(&nrec, 0, sizeof(nrec));

        /*
         * If we made it to the root level, allocate a new root block
         * and we're done.
         */
        if (level >= cur->bc_nlevels) {
                XFS_STATS_INC(xs_abt_insrec);
                if ((error = xfs_alloc_newroot(cur, &i)))
                        return error;
                *bnop = NULLAGBLOCK;
                *stat = i;
                return 0;
        }
        /*
         * Make a key out of the record data to be inserted, and save it.
         */
        key.ar_startblock = recp->ar_startblock;
        key.ar_blockcount = recp->ar_blockcount;
        optr = ptr = cur->bc_ptrs[level];
        /*
         * If we're off the left edge, return failure.
         */
        if (ptr == 0) {
                *stat = 0;
                return 0;
        }
        XFS_STATS_INC(xs_abt_insrec);
        /*
         * Get pointers to the btree buffer and block.
         */
        bp = cur->bc_bufs[level];
        block = XFS_BUF_TO_ALLOC_BLOCK(bp);
        numrecs = be16_to_cpu(block->bb_numrecs);
#ifdef DEBUG
        if ((error = xfs_btree_check_sblock(cur, block, level, bp)))
                return error;
        /*
         * Check that the new entry is being inserted in the right place.
         */
        if (ptr <= numrecs) {
                if (level == 0) {
                        rp = XFS_ALLOC_REC_ADDR(block, ptr, cur);
                        xfs_btree_check_rec(cur->bc_btnum, recp, rp);
                } else {
                        kp = XFS_ALLOC_KEY_ADDR(block, ptr, cur);
                        xfs_btree_check_key(cur->bc_btnum, &key, kp);
                }
        }
#endif
        nbno = NULLAGBLOCK;
        ncur = NULL;
        /*
         * If the block is full, we can't insert the new entry until we
         * make the block un-full.
         */
        if (numrecs == XFS_ALLOC_BLOCK_MAXRECS(level, cur)) {
                /*
                 * First, try shifting an entry to the right neighbor.
                 */
                if ((error = xfs_alloc_rshift(cur, level, &i)))
                        return error;
                if (i) {
                        /* nothing */
                }
                /*
                 * Next, try shifting an entry to the left neighbor.
                 */
                else {
                        if ((error = xfs_alloc_lshift(cur, level, &i)))
                                return error;
                        if (i)
                                optr = ptr = cur->bc_ptrs[level];
                        else {
                                /*
                                 * Next, try splitting the current block in
                                 * half. If this works we have to re-set our
                                 * variables because we could be in a
                                 * different block now.
                                 */
                                if ((error = xfs_alloc_split(cur, level, &nbno,
                                                &nkey, &ncur, &i)))
                                        return error;
                                if (i) {
                                        bp = cur->bc_bufs[level];
                                        block = XFS_BUF_TO_ALLOC_BLOCK(bp);
#ifdef DEBUG
                                        if ((error =
                                                xfs_btree_check_sblock(cur,
                                                        block, level, bp)))
                                                return error;
#endif
                                        ptr = cur->bc_ptrs[level];
                                        nrec.ar_startblock = nkey.ar_startblock;
                                        nrec.ar_blockcount = nkey.ar_blockcount;
                                }
                                /*
                                 * Otherwise the insert fails.
                                 */
                                else {
                                        *stat = 0;
                                        return 0;
                                }
                        }
                }
        }
        /*
         * At this point we know there's room for our new entry in the block
         * we're pointing at.
         */
        numrecs = be16_to_cpu(block->bb_numrecs);
        if (level > 0) {
                /*
                 * It's a non-leaf entry.  Make a hole for the new data
                 * in the key and ptr regions of the block.
                 */
                kp = XFS_ALLOC_KEY_ADDR(block, 1, cur);
                pp = XFS_ALLOC_PTR_ADDR(block, 1, cur);
#ifdef DEBUG
                for (i = numrecs; i >= ptr; i--) {
                        if ((error = xfs_btree_check_sptr(cur, be32_to_cpu(pp[i - 1]), level)))
                                return error;
                }
#endif
                memmove(&kp[ptr], &kp[ptr - 1],
                        (numrecs - ptr + 1) * sizeof(*kp));
                memmove(&pp[ptr], &pp[ptr - 1],
                        (numrecs - ptr + 1) * sizeof(*pp));
#ifdef DEBUG
                if ((error = xfs_btree_check_sptr(cur, *bnop, level)))
                        return error;
#endif
                /*
                 * Now stuff the new data in, bump numrecs and log the new data.
                 */
                kp[ptr - 1] = key;
                pp[ptr - 1] = cpu_to_be32(*bnop);
                numrecs++;
                block->bb_numrecs = cpu_to_be16(numrecs);
                xfs_alloc_log_keys(cur, bp, ptr, numrecs);
                xfs_alloc_log_ptrs(cur, bp, ptr, numrecs);
#ifdef DEBUG
                if (ptr < numrecs)
                        xfs_btree_check_key(cur->bc_btnum, kp + ptr - 1,
                                kp + ptr);
#endif
        } else {
                /*
                 * It's a leaf entry.  Make a hole for the new record.
                 */
                rp = XFS_ALLOC_REC_ADDR(block, 1, cur);
                memmove(&rp[ptr], &rp[ptr - 1],
                        (numrecs - ptr + 1) * sizeof(*rp));
                /*
                 * Now stuff the new record in, bump numrecs
                 * and log the new data.
                 */
                rp[ptr - 1] = *recp;
                numrecs++;
                block->bb_numrecs = cpu_to_be16(numrecs);
                xfs_alloc_log_recs(cur, bp, ptr, numrecs);
#ifdef DEBUG
                if (ptr < numrecs)
                        xfs_btree_check_rec(cur->bc_btnum, rp + ptr - 1,
                                rp + ptr);
#endif
        }
        /*
         * Log the new number of records in the btree header.
         */
        xfs_alloc_log_block(cur->bc_tp, bp, XFS_BB_NUMRECS);
        /*
         * If we inserted at the start of a block, update the parents' keys.
         */
        if (optr == 1 && (error = xfs_alloc_updkey(cur, &key, level + 1)))
                return error;
        /*
         * Look to see if the longest extent in the allocation group
         * needs to be updated.
         */

        agf = XFS_BUF_TO_AGF(cur->bc_private.a.agbp);
        if (level == 0 &&
            cur->bc_btnum == XFS_BTNUM_CNT &&
            be32_to_cpu(block->bb_rightsib) == NULLAGBLOCK &&
            be32_to_cpu(recp->ar_blockcount) > be32_to_cpu(agf->agf_longest)) {
                /*
                 * If this is a leaf in the by-size btree and there
                 * is no right sibling block and this block is bigger
                 * than the previous longest block, update it.
                 */
                agf->agf_longest = recp->ar_blockcount;
                cur->bc_mp->m_perag[be32_to_cpu(agf->agf_seqno)].pagf_longest
                        = be32_to_cpu(recp->ar_blockcount);
                xfs_alloc_log_agf(cur->bc_tp, cur->bc_private.a.agbp,
                        XFS_AGF_LONGEST);
        }
        /*
         * Return the new block number, if any.
         * If there is one, give back a record value and a cursor too.
         */
        *bnop = nbno;
        if (nbno != NULLAGBLOCK) {
                *recp = nrec;
                *curp = ncur;
        }
        *stat = 1;
        return 0;
}

/*
 * Log header fields from a btree block.
 */
STATIC void
xfs_alloc_log_block(
        xfs_trans_t             *tp,    /* transaction pointer */
        xfs_buf_t               *bp,    /* buffer containing btree block */
        int                     fields) /* mask of fields: XFS_BB_... */
{
        int                     first;  /* first byte offset logged */
        int                     last;   /* last byte offset logged */
        static const short      offsets[] = {   /* table of offsets */
                offsetof(xfs_alloc_block_t, bb_magic),
                offsetof(xfs_alloc_block_t, bb_level),
                offsetof(xfs_alloc_block_t, bb_numrecs),
                offsetof(xfs_alloc_block_t, bb_leftsib),
                offsetof(xfs_alloc_block_t, bb_rightsib),
                sizeof(xfs_alloc_block_t)
        };

        xfs_btree_offsets(fields, offsets, XFS_BB_NUM_BITS, &first, &last);
        xfs_trans_log_buf(tp, bp, first, last);
}

/*
 * Log keys from a btree block (nonleaf).
 */
STATIC void
xfs_alloc_log_keys(
        xfs_btree_cur_t         *cur,   /* btree cursor */
        xfs_buf_t               *bp,    /* buffer containing btree block */
        int                     kfirst, /* index of first key to log */
        int                     klast)  /* index of last key to log */
{
        xfs_alloc_block_t       *block; /* btree block to log from */
        int                     first;  /* first byte offset logged */
        xfs_alloc_key_t         *kp;    /* key pointer in btree block */
        int                     last;   /* last byte offset logged */

        block = XFS_BUF_TO_ALLOC_BLOCK(bp);
        kp = XFS_ALLOC_KEY_ADDR(block, 1, cur);
        first = (int)((xfs_caddr_t)&kp[kfirst - 1] - (xfs_caddr_t)block);
        last = (int)(((xfs_caddr_t)&kp[klast] - 1) - (xfs_caddr_t)block);
        xfs_trans_log_buf(cur->bc_tp, bp, first, last);
}

/*
 * Log block pointer fields from a btree block (nonleaf).
 */
STATIC void
xfs_alloc_log_ptrs(
        xfs_btree_cur_t         *cur,   /* btree cursor */
        xfs_buf_t               *bp,    /* buffer containing btree block */
        int                     pfirst, /* index of first pointer to log */
        int                     plast)  /* index of last pointer to log */
{
        xfs_alloc_block_t       *block; /* btree block to log from */
        int                     first;  /* first byte offset logged */
        int                     last;   /* last byte offset logged */
        xfs_alloc_ptr_t         *pp;    /* block-pointer pointer in btree blk */

        block = XFS_BUF_TO_ALLOC_BLOCK(bp);
        pp = XFS_ALLOC_PTR_ADDR(block, 1, cur);
        first = (int)((xfs_caddr_t)&pp[pfirst - 1] - (xfs_caddr_t)block);
        last = (int)(((xfs_caddr_t)&pp[plast] - 1) - (xfs_caddr_t)block);
        xfs_trans_log_buf(cur->bc_tp, bp, first, last);
}

/*
 * Log records from a btree block (leaf).
 */
STATIC void
xfs_alloc_log_recs(
        xfs_btree_cur_t         *cur,   /* btree cursor */
        xfs_buf_t               *bp,    /* buffer containing btree block */
        int                     rfirst, /* index of first record to log */
        int                     rlast)  /* index of last record to log */
{
        xfs_alloc_block_t       *block; /* btree block to log from */
        int                     first;  /* first byte offset logged */
        int                     last;   /* last byte offset logged */
        xfs_alloc_rec_t         *rp;    /* record pointer for btree block */


        block = XFS_BUF_TO_ALLOC_BLOCK(bp);
        rp = XFS_ALLOC_REC_ADDR(block, 1, cur);
#ifdef DEBUG
        {
                xfs_agf_t       *agf;
                xfs_alloc_rec_t *p;

                agf = XFS_BUF_TO_AGF(cur->bc_private.a.agbp);
                for (p = &rp[rfirst - 1]; p <= &rp[rlast - 1]; p++)
                        ASSERT(be32_to_cpu(p->ar_startblock) +
                               be32_to_cpu(p->ar_blockcount) <=
                               be32_to_cpu(agf->agf_length));
        }
#endif
        first = (int)((xfs_caddr_t)&rp[rfirst - 1] - (xfs_caddr_t)block);
        last = (int)(((xfs_caddr_t)&rp[rlast] - 1) - (xfs_caddr_t)block);
        xfs_trans_log_buf(cur->bc_tp, bp, first, last);
}

/*
 * Lookup the record.  The cursor is made to point to it, based on dir.
 * Return 0 if can't find any such record, 1 for success.
 */
STATIC int                              /* error */
xfs_alloc_lookup(
        xfs_btree_cur_t         *cur,   /* btree cursor */
        xfs_lookup_t            dir,    /* <=, ==, or >= */
        int                     *stat)  /* success/failure */
{
        xfs_agblock_t           agbno;  /* a.g. relative btree block number */
        xfs_agnumber_t          agno;   /* allocation group number */
        xfs_alloc_block_t       *block=NULL;    /* current btree block */
        int                     diff;   /* difference for the current key */
        int                     error;  /* error return value */
        int                     keyno=0;        /* current key number */
        int                     level;  /* level in the btree */
        xfs_mount_t             *mp;    /* file system mount point */

        XFS_STATS_INC(xs_abt_lookup);
        /*
         * Get the allocation group header, and the root block number.
         */
        mp = cur->bc_mp;

        {
                xfs_agf_t       *agf;   /* a.g. freespace header */

                agf = XFS_BUF_TO_AGF(cur->bc_private.a.agbp);
                agno = be32_to_cpu(agf->agf_seqno);
                agbno = be32_to_cpu(agf->agf_roots[cur->bc_btnum]);
        }
        /*
         * Iterate over each level in the btree, starting at the root.
         * For each level above the leaves, find the key we need, based
         * on the lookup record, then follow the corresponding block
         * pointer down to the next level.
         */
        for (level = cur->bc_nlevels - 1, diff = 1; level >= 0; level--) {
                xfs_buf_t       *bp;    /* buffer pointer for btree block */
                xfs_daddr_t     d;      /* disk address of btree block */

                /*
                 * Get the disk address we're looking for.
                 */
                d = XFS_AGB_TO_DADDR(mp, agno, agbno);
                /*
                 * If the old buffer at this level is for a different block,
                 * throw it away, otherwise just use it.
                 */
                bp = cur->bc_bufs[level];
                if (bp && XFS_BUF_ADDR(bp) != d)
                        bp = NULL;
                if (!bp) {
                        /*
                         * Need to get a new buffer.  Read it, then
                         * set it in the cursor, releasing the old one.
                         */
                        if ((error = xfs_btree_read_bufs(mp, cur->bc_tp, agno,
                                        agbno, 0, &bp, XFS_ALLOC_BTREE_REF)))
                                return error;
                        xfs_btree_setbuf(cur, level, bp);
                        /*
                         * Point to the btree block, now that we have the buffer
                         */
                        block = XFS_BUF_TO_ALLOC_BLOCK(bp);
                        if ((error = xfs_btree_check_sblock(cur, block, level,
                                        bp)))
                                return error;
                } else
                        block = XFS_BUF_TO_ALLOC_BLOCK(bp);
                /*
                 * If we already had a key match at a higher level, we know
                 * we need to use the first entry in this block.
                 */
                if (diff == 0)
                        keyno = 1;
                /*
                 * Otherwise we need to search this block.  Do a binary search.
                 */
                else {
                        int             high;   /* high entry number */
                        xfs_alloc_key_t *kkbase=NULL;/* base of keys in block */
                        xfs_alloc_rec_t *krbase=NULL;/* base of records in block */
                        int             low;    /* low entry number */

                        /*
                         * Get a pointer to keys or records.
                         */
                        if (level > 0)
                                kkbase = XFS_ALLOC_KEY_ADDR(block, 1, cur);
                        else
                                krbase = XFS_ALLOC_REC_ADDR(block, 1, cur);
                        /*
                         * Set low and high entry numbers, 1-based.
                         */
                        low = 1;
                        if (!(high = be16_to_cpu(block->bb_numrecs))) {
                                /*
                                 * If the block is empty, the tree must
                                 * be an empty leaf.
                                 */
                                ASSERT(level == 0 && cur->bc_nlevels == 1);
                                cur->bc_ptrs[0] = dir != XFS_LOOKUP_LE;
                                *stat = 0;
                                return 0;
                        }
                        /*
                         * Binary search the block.
                         */
                        while (low <= high) {
                                xfs_extlen_t    blockcount;     /* key value */
                                xfs_agblock_t   startblock;     /* key value */

                                XFS_STATS_INC(xs_abt_compare);
                                /*
                                 * keyno is average of low and high.
                                 */
                                keyno = (low + high) >> 1;
                                /*
                                 * Get startblock & blockcount.
                                 */
                                if (level > 0) {
                                        xfs_alloc_key_t *kkp;

                                        kkp = kkbase + keyno - 1;
                                        startblock = be32_to_cpu(kkp->ar_startblock);
                                        blockcount = be32_to_cpu(kkp->ar_blockcount);
                                } else {
                                        xfs_alloc_rec_t *krp;

                                        krp = krbase + keyno - 1;
                                        startblock = be32_to_cpu(krp->ar_startblock);
                                        blockcount = be32_to_cpu(krp->ar_blockcount);
                                }
                                /*
                                 * Compute difference to get next direction.
                                 */
                                if (cur->bc_btnum == XFS_BTNUM_BNO)
                                        diff = (int)startblock -
                                               (int)cur->bc_rec.a.ar_startblock;
                                else if (!(diff = (int)blockcount -
                                            (int)cur->bc_rec.a.ar_blockcount))
                                        diff = (int)startblock -
                                            (int)cur->bc_rec.a.ar_startblock;
                                /*
                                 * Less than, move right.
                                 */
                                if (diff < 0)
                                        low = keyno + 1;
                                /*
                                 * Greater than, move left.
                                 */
                                else if (diff > 0)
                                        high = keyno - 1;
                                /*
                                 * Equal, we're done.
                                 */
                                else
                                        break;
                        }
                }
                /*
                 * If there are more levels, set up for the next level
                 * by getting the block number and filling in the cursor.
                 */
                if (level > 0) {
                        /*
                         * If we moved left, need the previous key number,
                         * unless there isn't one.
                         */
                        if (diff > 0 && --keyno < 1)
                                keyno = 1;
                        agbno = be32_to_cpu(*XFS_ALLOC_PTR_ADDR(block, keyno, cur));
#ifdef DEBUG
                        if ((error = xfs_btree_check_sptr(cur, agbno, level)))
                                return error;
#endif
                        cur->bc_ptrs[level] = keyno;
                }
        }
        /*
         * Done with the search.
         * See if we need to adjust the results.
         */
        if (dir != XFS_LOOKUP_LE && diff < 0) {
                keyno++;
                /*
                 * If ge search and we went off the end of the block, but it's
                 * not the last block, we're in the wrong block.
                 */
                if (dir == XFS_LOOKUP_GE &&
                    keyno > be16_to_cpu(block->bb_numrecs) &&
                    be32_to_cpu(block->bb_rightsib) != NULLAGBLOCK) {
                        int     i;

                        cur->bc_ptrs[0] = keyno;
                        if ((error = xfs_alloc_increment(cur, 0, &i)))
                                return error;
                        XFS_WANT_CORRUPTED_RETURN(i == 1);
                        *stat = 1;
                        return 0;
                }
        }
        else if (dir == XFS_LOOKUP_LE && diff > 0)
                keyno--;
        cur->bc_ptrs[0] = keyno;
        /*
         * Return if we succeeded or not.
         */
        if (keyno == 0 || keyno > be16_to_cpu(block->bb_numrecs))
                *stat = 0;
        else
                *stat = ((dir != XFS_LOOKUP_EQ) || (diff == 0));
        return 0;
}

/*
 * Move 1 record left from cur/level if possible.
 * Update cur to reflect the new path.
 */
STATIC int                              /* error */
xfs_alloc_lshift(
        xfs_btree_cur_t         *cur,   /* btree cursor */
        int                     level,  /* level to shift record on */
        int                     *stat)  /* success/failure */
{
        int                     error;  /* error return value */
#ifdef DEBUG
        int                     i;      /* loop index */
#endif
        xfs_alloc_key_t         key;    /* key value for leaf level upward */
        xfs_buf_t               *lbp;   /* buffer for left neighbor block */
        xfs_alloc_block_t       *left;  /* left neighbor btree block */
        int                     nrec;   /* new number of left block entries */
        xfs_buf_t               *rbp;   /* buffer for right (current) block */
        xfs_alloc_block_t       *right; /* right (current) btree block */
        xfs_alloc_key_t         *rkp=NULL;      /* key pointer for right block */
        xfs_alloc_ptr_t         *rpp=NULL;      /* address pointer for right block */
        xfs_alloc_rec_t         *rrp=NULL;      /* record pointer for right block */

        /*
         * Set up variables for this block as "right".
         */
        rbp = cur->bc_bufs[level];
        right = XFS_BUF_TO_ALLOC_BLOCK(rbp);
#ifdef DEBUG
        if ((error = xfs_btree_check_sblock(cur, right, level, rbp)))
                return error;
#endif
        /*
         * If we've got no left sibling then we can't shift an entry left.
         */
        if (be32_to_cpu(right->bb_leftsib) == NULLAGBLOCK) {
                *stat = 0;
                return 0;
        }
        /*
         * If the cursor entry is the one that would be moved, don't
         * do it... it's too complicated.
         */
        if (cur->bc_ptrs[level] <= 1) {
                *stat = 0;
                return 0;
        }
        /*
         * Set up the left neighbor as "left".
         */
        if ((error = xfs_btree_read_bufs(cur->bc_mp, cur->bc_tp,
                        cur->bc_private.a.agno, be32_to_cpu(right->bb_leftsib),
                        0, &lbp, XFS_ALLOC_BTREE_REF)))
                return error;
        left = XFS_BUF_TO_ALLOC_BLOCK(lbp);
        if ((error = xfs_btree_check_sblock(cur, left, level, lbp)))
                return error;
        /*
         * If it's full, it can't take another entry.
         */
        if (be16_to_cpu(left->bb_numrecs) == XFS_ALLOC_BLOCK_MAXRECS(level, cur)) {
                *stat = 0;
                return 0;
        }
        nrec = be16_to_cpu(left->bb_numrecs) + 1;
        /*
         * If non-leaf, copy a key and a ptr to the left block.
         */
        if (level > 0) {
                xfs_alloc_key_t *lkp;   /* key pointer for left block */
                xfs_alloc_ptr_t *lpp;   /* address pointer for left block */

                lkp = XFS_ALLOC_KEY_ADDR(left, nrec, cur);
                rkp = XFS_ALLOC_KEY_ADDR(right, 1, cur);
                *lkp = *rkp;
                xfs_alloc_log_keys(cur, lbp, nrec, nrec);
                lpp = XFS_ALLOC_PTR_ADDR(left, nrec, cur);
                rpp = XFS_ALLOC_PTR_ADDR(right, 1, cur);
#ifdef DEBUG
                if ((error = xfs_btree_check_sptr(cur, be32_to_cpu(*rpp), level)))
                        return error;
#endif
                *lpp = *rpp;
                xfs_alloc_log_ptrs(cur, lbp, nrec, nrec);
                xfs_btree_check_key(cur->bc_btnum, lkp - 1, lkp);
        }
        /*
         * If leaf, copy a record to the left block.
         */
        else {
                xfs_alloc_rec_t *lrp;   /* record pointer for left block */

                lrp = XFS_ALLOC_REC_ADDR(left, nrec, cur);
                rrp = XFS_ALLOC_REC_ADDR(right, 1, cur);
                *lrp = *rrp;
                xfs_alloc_log_recs(cur, lbp, nrec, nrec);
                xfs_btree_check_rec(cur->bc_btnum, lrp - 1, lrp);
        }
        /*
         * Bump and log left's numrecs, decrement and log right's numrecs.
         */
        be16_add(&left->bb_numrecs, 1);
        xfs_alloc_log_block(cur->bc_tp, lbp, XFS_BB_NUMRECS);
        be16_add(&right->bb_numrecs, -1);
        xfs_alloc_log_block(cur->bc_tp, rbp, XFS_BB_NUMRECS);
        /*
         * Slide the contents of right down one entry.
         */
        if (level > 0) {
#ifdef DEBUG
                for (i = 0; i < be16_to_cpu(right->bb_numrecs); i++) {
                        if ((error = xfs_btree_check_sptr(cur, be32_to_cpu(rpp[i + 1]),
                                        level)))
                                return error;
                }
#endif
                memmove(rkp, rkp + 1, be16_to_cpu(right->bb_numrecs) * sizeof(*rkp));
                memmove(rpp, rpp + 1, be16_to_cpu(right->bb_numrecs) * sizeof(*rpp));
                xfs_alloc_log_keys(cur, rbp, 1, be16_to_cpu(right->bb_numrecs));
                xfs_alloc_log_ptrs(cur, rbp, 1, be16_to_cpu(right->bb_numrecs));
        } else {
                memmove(rrp, rrp + 1, be16_to_cpu(right->bb_numrecs) * sizeof(*rrp));
                xfs_alloc_log_recs(cur, rbp, 1, be16_to_cpu(right->bb_numrecs));
                key.ar_startblock = rrp->ar_startblock;
                key.ar_blockcount = rrp->ar_blockcount;
                rkp = &key;
        }
        /*
         * Update the parent key values of right.
         */
        if ((error = xfs_alloc_updkey(cur, rkp, level + 1)))
                return error;
        /*
         * Slide the cursor value left one.
         */
        cur->bc_ptrs[level]--;
        *stat = 1;
        return 0;
}

/*
 * Allocate a new root block, fill it in.
 */
STATIC int                              /* error */
xfs_alloc_newroot(
        xfs_btree_cur_t         *cur,   /* btree cursor */
        int                     *stat)  /* success/failure */
{
        int                     error;  /* error return value */
        xfs_agblock_t           lbno;   /* left block number */
        xfs_buf_t               *lbp;   /* left btree buffer */
        xfs_alloc_block_t       *left;  /* left btree block */
        xfs_mount_t             *mp;    /* mount structure */
        xfs_agblock_t           nbno;   /* new block number */
        xfs_buf_t               *nbp;   /* new (root) buffer */
        xfs_alloc_block_t       *new;   /* new (root) btree block */
        int                     nptr;   /* new value for key index, 1 or 2 */
        xfs_agblock_t           rbno;   /* right block number */
        xfs_buf_t               *rbp;   /* right btree buffer */
        xfs_alloc_block_t       *right; /* right btree block */

        mp = cur->bc_mp;

        ASSERT(cur->bc_nlevels < XFS_AG_MAXLEVELS(mp));
        /*
         * Get a buffer from the freelist blocks, for the new root.
         */
        if ((error = xfs_alloc_get_freelist(cur->bc_tp, cur->bc_private.a.agbp,
                        &nbno)))
                return error;
        /*
         * None available, we fail.
         */
        if (nbno == NULLAGBLOCK) {
                *stat = 0;
                return 0;
        }
        xfs_trans_agbtree_delta(cur->bc_tp, 1);
        nbp = xfs_btree_get_bufs(mp, cur->bc_tp, cur->bc_private.a.agno, nbno,
                0);
        new = XFS_BUF_TO_ALLOC_BLOCK(nbp);
        /*
         * Set the root data in the a.g. freespace structure.
         */
        {
                xfs_agf_t       *agf;   /* a.g. freespace header */
                xfs_agnumber_t  seqno;

                agf = XFS_BUF_TO_AGF(cur->bc_private.a.agbp);
                agf->agf_roots[cur->bc_btnum] = cpu_to_be32(nbno);
                be32_add(&agf->agf_levels[cur->bc_btnum], 1);
                seqno = be32_to_cpu(agf->agf_seqno);
                mp->m_perag[seqno].pagf_levels[cur->bc_btnum]++;
                xfs_alloc_log_agf(cur->bc_tp, cur->bc_private.a.agbp,
                        XFS_AGF_ROOTS | XFS_AGF_LEVELS);
        }
        /*
         * At the previous root level there are now two blocks: the old
         * root, and the new block generated when it was split.
         * We don't know which one the cursor is pointing at, so we
         * set up variables "left" and "right" for each case.
         */
        lbp = cur->bc_bufs[cur->bc_nlevels - 1];
        left = XFS_BUF_TO_ALLOC_BLOCK(lbp);
#ifdef DEBUG
        if ((error = xfs_btree_check_sblock(cur, left, cur->bc_nlevels - 1, lbp)))
                return error;
#endif
        if (be32_to_cpu(left->bb_rightsib) != NULLAGBLOCK) {
                /*
                 * Our block is left, pick up the right block.
                 */
                lbno = XFS_DADDR_TO_AGBNO(mp, XFS_BUF_ADDR(lbp));
                rbno = be32_to_cpu(left->bb_rightsib);
                if ((error = xfs_btree_read_bufs(mp, cur->bc_tp,
                                cur->bc_private.a.agno, rbno, 0, &rbp,
                                XFS_ALLOC_BTREE_REF)))
                        return error;
                right = XFS_BUF_TO_ALLOC_BLOCK(rbp);
                if ((error = xfs_btree_check_sblock(cur, right,
                                cur->bc_nlevels - 1, rbp)))
                        return error;
                nptr = 1;
        } else {
                /*
                 * Our block is right, pick up the left block.
                 */
                rbp = lbp;
                right = left;
                rbno = XFS_DADDR_TO_AGBNO(mp, XFS_BUF_ADDR(rbp));
                lbno = be32_to_cpu(right->bb_leftsib);
                if ((error = xfs_btree_read_bufs(mp, cur->bc_tp,
                                cur->bc_private.a.agno, lbno, 0, &lbp,
                                XFS_ALLOC_BTREE_REF)))
                        return error;
                left = XFS_BUF_TO_ALLOC_BLOCK(lbp);
                if ((error = xfs_btree_check_sblock(cur, left,
                                cur->bc_nlevels - 1, lbp)))
                        return error;
                nptr = 2;
        }
        /*
         * Fill in the new block's btree header and log it.
         */
        new->bb_magic = cpu_to_be32(xfs_magics[cur->bc_btnum]);
        new->bb_level = cpu_to_be16(cur->bc_nlevels);
        new->bb_numrecs = cpu_to_be16(2);
        new->bb_leftsib = cpu_to_be32(NULLAGBLOCK);
        new->bb_rightsib = cpu_to_be32(NULLAGBLOCK);
        xfs_alloc_log_block(cur->bc_tp, nbp, XFS_BB_ALL_BITS);
        ASSERT(lbno != NULLAGBLOCK && rbno != NULLAGBLOCK);
        /*
         * Fill in the key data in the new root.
         */
        {
                xfs_alloc_key_t         *kp;    /* btree key pointer */

                kp = XFS_ALLOC_KEY_ADDR(new, 1, cur);
                if (be16_to_cpu(left->bb_level) > 0) {
                        kp[0] = *XFS_ALLOC_KEY_ADDR(left, 1, cur);
                        kp[1] = *XFS_ALLOC_KEY_ADDR(right, 1, cur);
                } else {
                        xfs_alloc_rec_t *rp;    /* btree record pointer */

                        rp = XFS_ALLOC_REC_ADDR(left, 1, cur);
                        kp[0].ar_startblock = rp->ar_startblock;
                        kp[0].ar_blockcount = rp->ar_blockcount;
                        rp = XFS_ALLOC_REC_ADDR(right, 1, cur);
                        kp[1].ar_startblock = rp->ar_startblock;
                        kp[1].ar_blockcount = rp->ar_blockcount;
                }
        }
        xfs_alloc_log_keys(cur, nbp, 1, 2);
        /*
         * Fill in the pointer data in the new root.
         */
        {
                xfs_alloc_ptr_t         *pp;    /* btree address pointer */

                pp = XFS_ALLOC_PTR_ADDR(new, 1, cur);
                pp[0] = cpu_to_be32(lbno);
                pp[1] = cpu_to_be32(rbno);
        }
        xfs_alloc_log_ptrs(cur, nbp, 1, 2);
        /*
         * Fix up the cursor.
         */
        xfs_btree_setbuf(cur, cur->bc_nlevels, nbp);
        cur->bc_ptrs[cur->bc_nlevels] = nptr;
        cur->bc_nlevels++;
        *stat = 1;
        return 0;
}

/*
 * Move 1 record right from cur/level if possible.
 * Update cur to reflect the new path.
 */
STATIC int                              /* error */
xfs_alloc_rshift(
        xfs_btree_cur_t         *cur,   /* btree cursor */
        int                     level,  /* level to shift record on */
        int                     *stat)  /* success/failure */
{
        int                     error;  /* error return value */
        int                     i;      /* loop index */
        xfs_alloc_key_t         key;    /* key value for leaf level upward */
        xfs_buf_t               *lbp;   /* buffer for left (current) block */
        xfs_alloc_block_t       *left;  /* left (current) btree block */
        xfs_buf_t               *rbp;   /* buffer for right neighbor block */
        xfs_alloc_block_t       *right; /* right neighbor btree block */
        xfs_alloc_key_t         *rkp;   /* key pointer for right block */
        xfs_btree_cur_t         *tcur;  /* temporary cursor */

        /*
         * Set up variables for this block as "left".
         */
        lbp = cur->bc_bufs[level];
        left = XFS_BUF_TO_ALLOC_BLOCK(lbp);
#ifdef DEBUG
        if ((error = xfs_btree_check_sblock(cur, left, level, lbp)))
                return error;
#endif
        /*
         * If we've got no right sibling then we can't shift an entry right.
         */
        if (be32_to_cpu(left->bb_rightsib) == NULLAGBLOCK) {
                *stat = 0;
                return 0;
        }
        /*
         * If the cursor entry is the one that would be moved, don't
         * do it... it's too complicated.
         */
        if (cur->bc_ptrs[level] >= be16_to_cpu(left->bb_numrecs)) {
                *stat = 0;
                return 0;
        }
        /*
         * Set up the right neighbor as "right".
         */
        if ((error = xfs_btree_read_bufs(cur->bc_mp, cur->bc_tp,
                        cur->bc_private.a.agno, be32_to_cpu(left->bb_rightsib),
                        0, &rbp, XFS_ALLOC_BTREE_REF)))
                return error;
        right = XFS_BUF_TO_ALLOC_BLOCK(rbp);
        if ((error = xfs_btree_check_sblock(cur, right, level, rbp)))
                return error;
        /*
         * If it's full, it can't take another entry.
         */
        if (be16_to_cpu(right->bb_numrecs) == XFS_ALLOC_BLOCK_MAXRECS(level, cur)) {
                *stat = 0;
                return 0;
        }
        /*
         * Make a hole at the start of the right neighbor block, then
         * copy the last left block entry to the hole.
         */
        if (level > 0) {
                xfs_alloc_key_t *lkp;   /* key pointer for left block */
                xfs_alloc_ptr_t *lpp;   /* address pointer for left block */
                xfs_alloc_ptr_t *rpp;   /* address pointer for right block */

                lkp = XFS_ALLOC_KEY_ADDR(left, be16_to_cpu(left->bb_numrecs), cur);
                lpp = XFS_ALLOC_PTR_ADDR(left, be16_to_cpu(left->bb_numrecs), cur);
                rkp = XFS_ALLOC_KEY_ADDR(right, 1, cur);
                rpp = XFS_ALLOC_PTR_ADDR(right, 1, cur);
#ifdef DEBUG
                for (i = be16_to_cpu(right->bb_numrecs) - 1; i >= 0; i--) {
                        if ((error = xfs_btree_check_sptr(cur, be32_to_cpu(rpp[i]), level)))
                                return error;
                }
#endif
                memmove(rkp + 1, rkp, be16_to_cpu(right->bb_numrecs) * sizeof(*rkp));
                memmove(rpp + 1, rpp, be16_to_cpu(right->bb_numrecs) * sizeof(*rpp));
#ifdef DEBUG
                if ((error = xfs_btree_check_sptr(cur, be32_to_cpu(*lpp), level)))
                        return error;
#endif
                *rkp = *lkp;
                *rpp = *lpp;
                xfs_alloc_log_keys(cur, rbp, 1, be16_to_cpu(right->bb_numrecs) + 1);
                xfs_alloc_log_ptrs(cur, rbp, 1, be16_to_cpu(right->bb_numrecs) + 1);
                xfs_btree_check_key(cur->bc_btnum, rkp, rkp + 1);
        } else {
                xfs_alloc_rec_t *lrp;   /* record pointer for left block */
                xfs_alloc_rec_t *rrp;   /* record pointer for right block */

                lrp = XFS_ALLOC_REC_ADDR(left, be16_to_cpu(left->bb_numrecs), cur);
                rrp = XFS_ALLOC_REC_ADDR(right, 1, cur);
                memmove(rrp + 1, rrp, be16_to_cpu(right->bb_numrecs) * sizeof(*rrp));
                *rrp = *lrp;
                xfs_alloc_log_recs(cur, rbp, 1, be16_to_cpu(right->bb_numrecs) + 1);
                key.ar_startblock = rrp->ar_startblock;
                key.ar_blockcount = rrp->ar_blockcount;
                rkp = &key;
                xfs_btree_check_rec(cur->bc_btnum, rrp, rrp + 1);
        }
        /*
         * Decrement and log left's numrecs, bump and log right's numrecs.
         */
        be16_add(&left->bb_numrecs, -1);
        xfs_alloc_log_block(cur->bc_tp, lbp, XFS_BB_NUMRECS);
        be16_add(&right->bb_numrecs, 1);
        xfs_alloc_log_block(cur->bc_tp, rbp, XFS_BB_NUMRECS);
        /*
         * Using a temporary cursor, update the parent key values of the
         * block on the right.
         */
        if ((error = xfs_btree_dup_cursor(cur, &tcur)))
                return error;
        i = xfs_btree_lastrec(tcur, level);
        XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
        if ((error = xfs_alloc_increment(tcur, level, &i)) ||
            (error = xfs_alloc_updkey(tcur, rkp, level + 1)))
                goto error0;
        xfs_btree_del_cursor(tcur, XFS_BTREE_NOERROR);
        *stat = 1;
        return 0;
error0:
        xfs_btree_del_cursor(tcur, XFS_BTREE_ERROR);
        return error;
}

/*
 * Split cur/level block in half.
 * Return new block number and its first record (to be inserted into parent).
 */
STATIC int                              /* error */
xfs_alloc_split(
        xfs_btree_cur_t         *cur,   /* btree cursor */
        int                     level,  /* level to split */
        xfs_agblock_t           *bnop,  /* output: block number allocated */
        xfs_alloc_key_t         *keyp,  /* output: first key of new block */
        xfs_btree_cur_t         **curp, /* output: new cursor */
        int                     *stat)  /* success/failure */
{
        int                     error;  /* error return value */
        int                     i;      /* loop index/record number */
        xfs_agblock_t           lbno;   /* left (current) block number */
        xfs_buf_t               *lbp;   /* buffer for left block */
        xfs_alloc_block_t       *left;  /* left (current) btree block */
        xfs_agblock_t           rbno;   /* right (new) block number */
        xfs_buf_t               *rbp;   /* buffer for right block */
        xfs_alloc_block_t       *right; /* right (new) btree block */

        /*
         * Allocate the new block from the freelist.
         * If we can't do it, we're toast.  Give up.
         */
        if ((error = xfs_alloc_get_freelist(cur->bc_tp, cur->bc_private.a.agbp,
                        &rbno)))
                return error;
        if (rbno == NULLAGBLOCK) {
                *stat = 0;
                return 0;
        }
        xfs_trans_agbtree_delta(cur->bc_tp, 1);
        rbp = xfs_btree_get_bufs(cur->bc_mp, cur->bc_tp, cur->bc_private.a.agno,
                rbno, 0);
        /*
         * Set up the new block as "right".
         */
        right = XFS_BUF_TO_ALLOC_BLOCK(rbp);
        /*
         * "Left" is the current (according to the cursor) block.
         */
        lbp = cur->bc_bufs[level];
        left = XFS_BUF_TO_ALLOC_BLOCK(lbp);
#ifdef DEBUG
        if ((error = xfs_btree_check_sblock(cur, left, level, lbp)))
                return error;
#endif
        /*
         * Fill in the btree header for the new block.
         */
        right->bb_magic = cpu_to_be32(xfs_magics[cur->bc_btnum]);
        right->bb_level = left->bb_level;
        right->bb_numrecs = cpu_to_be16(be16_to_cpu(left->bb_numrecs) / 2);
        /*
         * Make sure that if there's an odd number of entries now, that
         * each new block will have the same number of entries.
         */
        if ((be16_to_cpu(left->bb_numrecs) & 1) &&
            cur->bc_ptrs[level] <= be16_to_cpu(right->bb_numrecs) + 1)
                be16_add(&right->bb_numrecs, 1);
        i = be16_to_cpu(left->bb_numrecs) - be16_to_cpu(right->bb_numrecs) + 1;
        /*
         * For non-leaf blocks, copy keys and addresses over to the new block.
         */
        if (level > 0) {
                xfs_alloc_key_t *lkp;   /* left btree key pointer */
                xfs_alloc_ptr_t *lpp;   /* left btree address pointer */
                xfs_alloc_key_t *rkp;   /* right btree key pointer */
                xfs_alloc_ptr_t *rpp;   /* right btree address pointer */

                lkp = XFS_ALLOC_KEY_ADDR(left, i, cur);
                lpp = XFS_ALLOC_PTR_ADDR(left, i, cur);
                rkp = XFS_ALLOC_KEY_ADDR(right, 1, cur);
                rpp = XFS_ALLOC_PTR_ADDR(right, 1, cur);
#ifdef DEBUG
                for (i = 0; i < be16_to_cpu(right->bb_numrecs); i++) {
                        if ((error = xfs_btree_check_sptr(cur, be32_to_cpu(lpp[i]), level)))
                                return error;
                }
#endif
                memcpy(rkp, lkp, be16_to_cpu(right->bb_numrecs) * sizeof(*rkp));
                memcpy(rpp, lpp, be16_to_cpu(right->bb_numrecs) * sizeof(*rpp));
                xfs_alloc_log_keys(cur, rbp, 1, be16_to_cpu(right->bb_numrecs));
                xfs_alloc_log_ptrs(cur, rbp, 1, be16_to_cpu(right->bb_numrecs));
                *keyp = *rkp;
        }
        /*
         * For leaf blocks, copy records over to the new block.
         */
        else {
                xfs_alloc_rec_t *lrp;   /* left btree record pointer */
                xfs_alloc_rec_t *rrp;   /* right btree record pointer */

                lrp = XFS_ALLOC_REC_ADDR(left, i, cur);
                rrp = XFS_ALLOC_REC_ADDR(right, 1, cur);
                memcpy(rrp, lrp, be16_to_cpu(right->bb_numrecs) * sizeof(*rrp));
                xfs_alloc_log_recs(cur, rbp, 1, be16_to_cpu(right->bb_numrecs));
                keyp->ar_startblock = rrp->ar_startblock;
                keyp->ar_blockcount = rrp->ar_blockcount;
        }
        /*
         * Find the left block number by looking in the buffer.
         * Adjust numrecs, sibling pointers.
         */
        lbno = XFS_DADDR_TO_AGBNO(cur->bc_mp, XFS_BUF_ADDR(lbp));
        be16_add(&left->bb_numrecs, -(be16_to_cpu(right->bb_numrecs)));
        right->bb_rightsib = left->bb_rightsib;
        left->bb_rightsib = cpu_to_be32(rbno);
        right->bb_leftsib = cpu_to_be32(lbno);
        xfs_alloc_log_block(cur->bc_tp, rbp, XFS_BB_ALL_BITS);
        xfs_alloc_log_block(cur->bc_tp, lbp, XFS_BB_NUMRECS | XFS_BB_RIGHTSIB);
        /*
         * If there's a block to the new block's right, make that block
         * point back to right instead of to left.
         */
        if (be32_to_cpu(right->bb_rightsib) != NULLAGBLOCK) {
                xfs_alloc_block_t       *rrblock;       /* rr btree block */
                xfs_buf_t               *rrbp;          /* buffer for rrblock */

                if ((error = xfs_btree_read_bufs(cur->bc_mp, cur->bc_tp,
                                cur->bc_private.a.agno, be32_to_cpu(right->bb_rightsib), 0,
                                &rrbp, XFS_ALLOC_BTREE_REF)))
                        return error;
                rrblock = XFS_BUF_TO_ALLOC_BLOCK(rrbp);
                if ((error = xfs_btree_check_sblock(cur, rrblock, level, rrbp)))
                        return error;
                rrblock->bb_leftsib = cpu_to_be32(rbno);
                xfs_alloc_log_block(cur->bc_tp, rrbp, XFS_BB_LEFTSIB);
        }
        /*
         * If the cursor is really in the right block, move it there.
         * If it's just pointing past the last entry in left, then we'll
         * insert there, so don't change anything in that case.
         */
        if (cur->bc_ptrs[level] > be16_to_cpu(left->bb_numrecs) + 1) {
                xfs_btree_setbuf(cur, level, rbp);
                cur->bc_ptrs[level] -= be16_to_cpu(left->bb_numrecs);
        }
        /*
         * If there are more levels, we'll need another cursor which refers to
         * the right block, no matter where this cursor was.
         */
        if (level + 1 < cur->bc_nlevels) {
                if ((error = xfs_btree_dup_cursor(cur, curp)))
                        return error;
                (*curp)->bc_ptrs[level + 1]++;
        }
        *bnop = rbno;
        *stat = 1;
        return 0;
}

/*
 * Update keys at all levels from here to the root along the cursor's path.
 */
STATIC int                              /* error */
xfs_alloc_updkey(
        xfs_btree_cur_t         *cur,   /* btree cursor */
        xfs_alloc_key_t         *keyp,  /* new key value to update to */
        int                     level)  /* starting level for update */
{
        int                     ptr;    /* index of key in block */

        /*
         * Go up the tree from this level toward the root.
         * At each level, update the key value to the value input.
         * Stop when we reach a level where the cursor isn't pointing
         * at the first entry in the block.
         */
        for (ptr = 1; ptr == 1 && level < cur->bc_nlevels; level++) {
                xfs_alloc_block_t       *block; /* btree block */
                xfs_buf_t               *bp;    /* buffer for block */
#ifdef DEBUG
                int                     error;  /* error return value */
#endif
                xfs_alloc_key_t         *kp;    /* ptr to btree block keys */

                bp = cur->bc_bufs[level];
                block = XFS_BUF_TO_ALLOC_BLOCK(bp);
#ifdef DEBUG
                if ((error = xfs_btree_check_sblock(cur, block, level, bp)))
                        return error;
#endif
                ptr = cur->bc_ptrs[level];
                kp = XFS_ALLOC_KEY_ADDR(block, ptr, cur);
                *kp = *keyp;
                xfs_alloc_log_keys(cur, bp, ptr, ptr);
        }
        return 0;
}

/*
 * Externally visible routines.
 */

/*
 * Decrement cursor by one record at the level.
 * For nonzero levels the leaf-ward information is untouched.
 */
int                                     /* error */
xfs_alloc_decrement(
        xfs_btree_cur_t         *cur,   /* btree cursor */
        int                     level,  /* level in btree, 0 is leaf */
        int                     *stat)  /* success/failure */
{
        xfs_alloc_block_t       *block; /* btree block */
        int                     error;  /* error return value */
        int                     lev;    /* btree level */

        ASSERT(level < cur->bc_nlevels);
        /*
         * Read-ahead to the left at this level.
         */
        xfs_btree_readahead(cur, level, XFS_BTCUR_LEFTRA);
        /*
         * Decrement the ptr at this level.  If we're still in the block
         * then we're done.
         */
        if (--cur->bc_ptrs[level] > 0) {
                *stat = 1;
                return 0;
        }
        /*
         * Get a pointer to the btree block.
         */
        block = XFS_BUF_TO_ALLOC_BLOCK(cur->bc_bufs[level]);
#ifdef DEBUG
        if ((error = xfs_btree_check_sblock(cur, block, level,
                        cur->bc_bufs[level])))
                return error;
#endif
        /*
         * If we just went off the left edge of the tree, return failure.
         */
        if (be32_to_cpu(block->bb_leftsib) == NULLAGBLOCK) {
                *stat = 0;
                return 0;
        }
        /*
         * March up the tree decrementing pointers.
         * Stop when we don't go off the left edge of a block.
         */
        for (lev = level + 1; lev < cur->bc_nlevels; lev++) {
                if (--cur->bc_ptrs[lev] > 0)
                        break;
                /*
                 * Read-ahead the left block, we're going to read it
                 * in the next loop.
                 */
                xfs_btree_readahead(cur, lev, XFS_BTCUR_LEFTRA);
        }
        /*
         * If we went off the root then we are seriously confused.
         */
        ASSERT(lev < cur->bc_nlevels);
        /*
         * Now walk back down the tree, fixing up the cursor's buffer
         * pointers and key numbers.
         */
        for (block = XFS_BUF_TO_ALLOC_BLOCK(cur->bc_bufs[lev]); lev > level; ) {
                xfs_agblock_t   agbno;  /* block number of btree block */
                xfs_buf_t       *bp;    /* buffer pointer for block */

                agbno = be32_to_cpu(*XFS_ALLOC_PTR_ADDR(block, cur->bc_ptrs[lev], cur));
                if ((error = xfs_btree_read_bufs(cur->bc_mp, cur->bc_tp,
                                cur->bc_private.a.agno, agbno, 0, &bp,
                                XFS_ALLOC_BTREE_REF)))
                        return error;
                lev--;
                xfs_btree_setbuf(cur, lev, bp);
                block = XFS_BUF_TO_ALLOC_BLOCK(bp);
                if ((error = xfs_btree_check_sblock(cur, block, lev, bp)))
                        return error;
                cur->bc_ptrs[lev] = be16_to_cpu(block->bb_numrecs);
        }
        *stat = 1;
        return 0;
}

/*
 * Delete the record pointed to by cur.
 * The cursor refers to the place where the record was (could be inserted)
 * when the operation returns.
 */
int                                     /* error */
xfs_alloc_delete(
        xfs_btree_cur_t *cur,           /* btree cursor */
        int             *stat)          /* success/failure */
{
        int             error;          /* error return value */
        int             i;              /* result code */
        int             level;          /* btree level */

        /*
         * Go up the tree, starting at leaf level.
         * If 2 is returned then a join was done; go to the next level.
         * Otherwise we are done.
         */
        for (level = 0, i = 2; i == 2; level++) {
                if ((error = xfs_alloc_delrec(cur, level, &i)))
                        return error;
        }
        if (i == 0) {
                for (level = 1; level < cur->bc_nlevels; level++) {
                        if (cur->bc_ptrs[level] == 0) {
                                if ((error = xfs_alloc_decrement(cur, level, &i)))
                                        return error;
                                break;
                        }
                }
        }
        *stat = i;
        return 0;
}

/*
 * Get the data from the pointed-to record.
 */
int                                     /* error */
xfs_alloc_get_rec(
        xfs_btree_cur_t         *cur,   /* btree cursor */
        xfs_agblock_t           *bno,   /* output: starting block of extent */
        xfs_extlen_t            *len,   /* output: length of extent */
        int                     *stat)  /* output: success/failure */
{
        xfs_alloc_block_t       *block; /* btree block */
#ifdef DEBUG
        int                     error;  /* error return value */
#endif
        int                     ptr;    /* record number */

        ptr = cur->bc_ptrs[0];
        block = XFS_BUF_TO_ALLOC_BLOCK(cur->bc_bufs[0]);
#ifdef DEBUG
        if ((error = xfs_btree_check_sblock(cur, block, 0, cur->bc_bufs[0])))
                return error;
#endif
        /*
         * Off the right end or left end, return failure.
         */
        if (ptr > be16_to_cpu(block->bb_numrecs) || ptr <= 0) {
                *stat = 0;
                return 0;
        }
        /*
         * Point to the record and extract its data.
         */
        {
                xfs_alloc_rec_t         *rec;   /* record data */

                rec = XFS_ALLOC_REC_ADDR(block, ptr, cur);
                *bno = be32_to_cpu(rec->ar_startblock);
                *len = be32_to_cpu(rec->ar_blockcount);
        }
        *stat = 1;
        return 0;
}

/*
 * Increment cursor by one record at the level.
 * For nonzero levels the leaf-ward information is untouched.
 */
int                                     /* error */
xfs_alloc_increment(
        xfs_btree_cur_t         *cur,   /* btree cursor */
        int                     level,  /* level in btree, 0 is leaf */
        int                     *stat)  /* success/failure */
{
        xfs_alloc_block_t       *block; /* btree block */
        xfs_buf_t               *bp;    /* tree block buffer */
        int                     error;  /* error return value */
        int                     lev;    /* btree level */

        ASSERT(level < cur->bc_nlevels);
        /*
         * Read-ahead to the right at this level.
         */
        xfs_btree_readahead(cur, level, XFS_BTCUR_RIGHTRA);
        /*
         * Get a pointer to the btree block.
         */
        bp = cur->bc_bufs[level];
        block = XFS_BUF_TO_ALLOC_BLOCK(bp);
#ifdef DEBUG
        if ((error = xfs_btree_check_sblock(cur, block, level, bp)))
                return error;
#endif
        /*
         * Increment the ptr at this level.  If we're still in the block
         * then we're done.
         */
        if (++cur->bc_ptrs[level] <= be16_to_cpu(block->bb_numrecs)) {
                *stat = 1;
                return 0;
        }
        /*
         * If we just went off the right edge of the tree, return failure.
         */
        if (be32_to_cpu(block->bb_rightsib) == NULLAGBLOCK) {
                *stat = 0;
                return 0;
        }
        /*
         * March up the tree incrementing pointers.
         * Stop when we don't go off the right edge of a block.
         */
        for (lev = level + 1; lev < cur->bc_nlevels; lev++) {
                bp = cur->bc_bufs[lev];
                block = XFS_BUF_TO_ALLOC_BLOCK(bp);
#ifdef DEBUG
                if ((error = xfs_btree_check_sblock(cur, block, lev, bp)))
                        return error;
#endif
                if (++cur->bc_ptrs[lev] <= be16_to_cpu(block->bb_numrecs))
                        break;
                /*
                 * Read-ahead the right block, we're going to read it
                 * in the next loop.
                 */
                xfs_btree_readahead(cur, lev, XFS_BTCUR_RIGHTRA);
        }
        /*
         * If we went off the root then we are seriously confused.
         */
        ASSERT(lev < cur->bc_nlevels);
        /*
         * Now walk back down the tree, fixing up the cursor's buffer
         * pointers and key numbers.
         */
        for (bp = cur->bc_bufs[lev], block = XFS_BUF_TO_ALLOC_BLOCK(bp);
             lev > level; ) {
                xfs_agblock_t   agbno;  /* block number of btree block */

                agbno = be32_to_cpu(*XFS_ALLOC_PTR_ADDR(block, cur->bc_ptrs[lev], cur));
                if ((error = xfs_btree_read_bufs(cur->bc_mp, cur->bc_tp,
                                cur->bc_private.a.agno, agbno, 0, &bp,
                                XFS_ALLOC_BTREE_REF)))
                        return error;
                lev--;
                xfs_btree_setbuf(cur, lev, bp);
                block = XFS_BUF_TO_ALLOC_BLOCK(bp);
                if ((error = xfs_btree_check_sblock(cur, block, lev, bp)))
                        return error;
                cur->bc_ptrs[lev] = 1;
        }
        *stat = 1;
        return 0;
}

/*
 * Insert the current record at the point referenced by cur.
 * The cursor may be inconsistent on return if splits have been done.
 */
int                                     /* error */
xfs_alloc_insert(
        xfs_btree_cur_t *cur,           /* btree cursor */
        int             *stat)          /* success/failure */
{
        int             error;          /* error return value */
        int             i;              /* result value, 0 for failure */
        int             level;          /* current level number in btree */
        xfs_agblock_t   nbno;           /* new block number (split result) */
        xfs_btree_cur_t *ncur;          /* new cursor (split result) */
        xfs_alloc_rec_t nrec;           /* record being inserted this level */
        xfs_btree_cur_t *pcur;          /* previous level's cursor */

        level = 0;
        nbno = NULLAGBLOCK;
        nrec.ar_startblock = cpu_to_be32(cur->bc_rec.a.ar_startblock);
        nrec.ar_blockcount = cpu_to_be32(cur->bc_rec.a.ar_blockcount);
        ncur = NULL;
        pcur = cur;
        /*
         * Loop going up the tree, starting at the leaf level.
         * Stop when we don't get a split block, that must mean that
         * the insert is finished with this level.
         */
        do {
                /*
                 * Insert nrec/nbno into this level of the tree.
                 * Note if we fail, nbno will be null.
                 */
                if ((error = xfs_alloc_insrec(pcur, level++, &nbno, &nrec, &ncur,
                                &i))) {
                        if (pcur != cur)
                                xfs_btree_del_cursor(pcur, XFS_BTREE_ERROR);
                        return error;
                }
                /*
                 * See if the cursor we just used is trash.
                 * Can't trash the caller's cursor, but otherwise we should
                 * if ncur is a new cursor or we're about to be done.
                 */
                if (pcur != cur && (ncur || nbno == NULLAGBLOCK)) {
                        cur->bc_nlevels = pcur->bc_nlevels;
                        xfs_btree_del_cursor(pcur, XFS_BTREE_NOERROR);
                }
                /*
                 * If we got a new cursor, switch to it.
                 */
                if (ncur) {
                        pcur = ncur;
                        ncur = NULL;
                }
        } while (nbno != NULLAGBLOCK);
        *stat = i;
        return 0;
}

/*
 * Lookup the record equal to [bno, len] in the btree given by cur.
 */
int                                     /* error */
xfs_alloc_lookup_eq(
        xfs_btree_cur_t *cur,           /* btree cursor */
        xfs_agblock_t   bno,            /* starting block of extent */
        xfs_extlen_t    len,            /* length of extent */
        int             *stat)          /* success/failure */
{
        cur->bc_rec.a.ar_startblock = bno;
        cur->bc_rec.a.ar_blockcount = len;
        return xfs_alloc_lookup(cur, XFS_LOOKUP_EQ, stat);
}

/*
 * Lookup the first record greater than or equal to [bno, len]
 * in the btree given by cur.
 */
int                                     /* error */
xfs_alloc_lookup_ge(
        xfs_btree_cur_t *cur,           /* btree cursor */
        xfs_agblock_t   bno,            /* starting block of extent */
        xfs_extlen_t    len,            /* length of extent */
        int             *stat)          /* success/failure */
{
        cur->bc_rec.a.ar_startblock = bno;
        cur->bc_rec.a.ar_blockcount = len;
        return xfs_alloc_lookup(cur, XFS_LOOKUP_GE, stat);
}

/*
 * Lookup the first record less than or equal to [bno, len]
 * in the btree given by cur.
 */
int                                     /* error */
xfs_alloc_lookup_le(
        xfs_btree_cur_t *cur,           /* btree cursor */
        xfs_agblock_t   bno,            /* starting block of extent */
        xfs_extlen_t    len,            /* length of extent */
        int             *stat)          /* success/failure */
{
        cur->bc_rec.a.ar_startblock = bno;
        cur->bc_rec.a.ar_blockcount = len;
        return xfs_alloc_lookup(cur, XFS_LOOKUP_LE, stat);
}

/*
 * Update the record referred to by cur, to the value given by [bno, len].
 * This either works (return 0) or gets an EFSCORRUPTED error.
 */
int                                     /* error */
xfs_alloc_update(
        xfs_btree_cur_t         *cur,   /* btree cursor */
        xfs_agblock_t           bno,    /* starting block of extent */
        xfs_extlen_t            len)    /* length of extent */
{
        xfs_alloc_block_t       *block; /* btree block to update */
        int                     error;  /* error return value */
        int                     ptr;    /* current record number (updating) */

        ASSERT(len > 0);
        /*
         * Pick up the a.g. freelist struct and the current block.
         */
        block = XFS_BUF_TO_ALLOC_BLOCK(cur->bc_bufs[0]);
#ifdef DEBUG
        if ((error = xfs_btree_check_sblock(cur, block, 0, cur->bc_bufs[0])))
                return error;
#endif
        /*
         * Get the address of the rec to be updated.
         */
        ptr = cur->bc_ptrs[0];
        {
                xfs_alloc_rec_t         *rp;    /* pointer to updated record */

                rp = XFS_ALLOC_REC_ADDR(block, ptr, cur);
                /*
                 * Fill in the new contents and log them.
                 */
                rp->ar_startblock = cpu_to_be32(bno);
                rp->ar_blockcount = cpu_to_be32(len);
                xfs_alloc_log_recs(cur, cur->bc_bufs[0], ptr, ptr);
        }
        /*
         * If it's the by-size btree and it's the last leaf block and
         * it's the last record... then update the size of the longest
         * extent in the a.g., which we cache in the a.g. freelist header.
         */
        if (cur->bc_btnum == XFS_BTNUM_CNT &&
            be32_to_cpu(block->bb_rightsib) == NULLAGBLOCK &&
            ptr == be16_to_cpu(block->bb_numrecs)) {
                xfs_agf_t       *agf;   /* a.g. freespace header */
                xfs_agnumber_t  seqno;

                agf = XFS_BUF_TO_AGF(cur->bc_private.a.agbp);
                seqno = be32_to_cpu(agf->agf_seqno);
                cur->bc_mp->m_perag[seqno].pagf_longest = len;
                agf->agf_longest = cpu_to_be32(len);
                xfs_alloc_log_agf(cur->bc_tp, cur->bc_private.a.agbp,
                        XFS_AGF_LONGEST);
        }
        /*
         * Updating first record in leaf. Pass new key value up to our parent.
         */
        if (ptr == 1) {
                xfs_alloc_key_t key;    /* key containing [bno, len] */

                key.ar_startblock = cpu_to_be32(bno);
                key.ar_blockcount = cpu_to_be32(len);
                if ((error = xfs_alloc_updkey(cur, &key, 1)))
                        return error;
        }
        return 0;
}