[XFS] implement generic xfs_btree_lshift

[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.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_newroot(xfs_btree_cur_t *, int *);
STATIC int xfs_alloc_split(xfs_btree_cur_t *, int, xfs_agblock_t *,
                xfs_alloc_key_t *, xfs_btree_cur_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_cpu(&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.
                         */
                        error = xfs_alloc_put_freelist(cur->bc_tp,
                                        cur->bc_private.a.agbp, NULL, bno, 1);
                        if (error)
                                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_btree_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_btree_updkey(cur, (union xfs_btree_key *)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_btree_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_btree_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_btree_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_btree_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_btree_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_btree_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_btree_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_btree_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_btree_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.
         */
        error = xfs_alloc_put_freelist(cur->bc_tp,
                                         cur->bc_private.a.agbp, NULL, rbno, 1);
        if (error)
                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_btree_rshift(cur, level, &i)))
                        return error;
                if (i) {
                        /* nothing */
                }
                /*
                 * Next, try shifting an entry to the left neighbor.
                 */
                else {
                        if ((error = xfs_btree_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_btree_updkey(cur, (union xfs_btree_key *)&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);
}

/*
 * 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.
         */
        error = xfs_alloc_get_freelist(cur->bc_tp,
                                        cur->bc_private.a.agbp, &nbno, 1);
        if (error)
                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_cpu(&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;
}

/*
 * 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.
         */
        error = xfs_alloc_get_freelist(cur->bc_tp,
                                         cur->bc_private.a.agbp, &rbno, 1);
        if (error)
                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_cpu(&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_cpu(&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;
}

/*
 * Externally visible routines.
 */

/*
 * 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_btree_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;
}

/*
 * 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;
}

STATIC struct xfs_btree_cur *
xfs_allocbt_dup_cursor(
        struct xfs_btree_cur    *cur)
{
        return xfs_allocbt_init_cursor(cur->bc_mp, cur->bc_tp,
                        cur->bc_private.a.agbp, cur->bc_private.a.agno,
                        cur->bc_btnum);
}

/*
 * Update the longest extent in the AGF
 */
STATIC void
xfs_allocbt_update_lastrec(
        struct xfs_btree_cur    *cur,
        struct xfs_btree_block  *block,
        union xfs_btree_rec     *rec,
        int                     ptr,
        int                     reason)
{
        struct xfs_agf          *agf = XFS_BUF_TO_AGF(cur->bc_private.a.agbp);
        xfs_agnumber_t          seqno = be32_to_cpu(agf->agf_seqno);
        __be32                  len;

        ASSERT(cur->bc_btnum == XFS_BTNUM_CNT);

        switch (reason) {
        case LASTREC_UPDATE:
                /*
                 * If this is the last leaf block and it's the last record,
                 * then update the size of the longest extent in the AG.
                 */
                if (ptr != xfs_btree_get_numrecs(block))
                        return;
                len = rec->alloc.ar_blockcount;
                break;
        default:
                ASSERT(0);
                return;
        }

        agf->agf_longest = len;
        cur->bc_mp->m_perag[seqno].pagf_longest = be32_to_cpu(len);
        xfs_alloc_log_agf(cur->bc_tp, cur->bc_private.a.agbp, XFS_AGF_LONGEST);
}

STATIC int
xfs_allocbt_get_maxrecs(
        struct xfs_btree_cur    *cur,
        int                     level)
{
        return cur->bc_mp->m_alloc_mxr[level != 0];
}

STATIC void
xfs_allocbt_init_key_from_rec(
        union xfs_btree_key     *key,
        union xfs_btree_rec     *rec)
{
        ASSERT(rec->alloc.ar_startblock != 0);

        key->alloc.ar_startblock = rec->alloc.ar_startblock;
        key->alloc.ar_blockcount = rec->alloc.ar_blockcount;
}

STATIC void
xfs_allocbt_init_ptr_from_cur(
        struct xfs_btree_cur    *cur,
        union xfs_btree_ptr     *ptr)
{
        struct xfs_agf          *agf = XFS_BUF_TO_AGF(cur->bc_private.a.agbp);

        ASSERT(cur->bc_private.a.agno == be32_to_cpu(agf->agf_seqno));
        ASSERT(agf->agf_roots[cur->bc_btnum] != 0);

        ptr->s = agf->agf_roots[cur->bc_btnum];
}

STATIC __int64_t
xfs_allocbt_key_diff(
        struct xfs_btree_cur    *cur,
        union xfs_btree_key     *key)
{
        xfs_alloc_rec_incore_t  *rec = &cur->bc_rec.a;
        xfs_alloc_key_t         *kp = &key->alloc;
        __int64_t               diff;

        if (cur->bc_btnum == XFS_BTNUM_BNO) {
                return (__int64_t)be32_to_cpu(kp->ar_startblock) -
                                rec->ar_startblock;
        }

        diff = (__int64_t)be32_to_cpu(kp->ar_blockcount) - rec->ar_blockcount;
        if (diff)
                return diff;

        return (__int64_t)be32_to_cpu(kp->ar_startblock) - rec->ar_startblock;
}

#ifdef XFS_BTREE_TRACE
ktrace_t        *xfs_allocbt_trace_buf;

STATIC void
xfs_allocbt_trace_enter(
        struct xfs_btree_cur    *cur,
        const char              *func,
        char                    *s,
        int                     type,
        int                     line,
        __psunsigned_t          a0,
        __psunsigned_t          a1,
        __psunsigned_t          a2,
        __psunsigned_t          a3,
        __psunsigned_t          a4,
        __psunsigned_t          a5,
        __psunsigned_t          a6,
        __psunsigned_t          a7,
        __psunsigned_t          a8,
        __psunsigned_t          a9,
        __psunsigned_t          a10)
{
        ktrace_enter(xfs_allocbt_trace_buf, (void *)(__psint_t)type,
                (void *)func, (void *)s, NULL, (void *)cur,
                (void *)a0, (void *)a1, (void *)a2, (void *)a3,
                (void *)a4, (void *)a5, (void *)a6, (void *)a7,
                (void *)a8, (void *)a9, (void *)a10);
}

STATIC void
xfs_allocbt_trace_cursor(
        struct xfs_btree_cur    *cur,
        __uint32_t              *s0,
        __uint64_t              *l0,
        __uint64_t              *l1)
{
        *s0 = cur->bc_private.a.agno;
        *l0 = cur->bc_rec.a.ar_startblock;
        *l1 = cur->bc_rec.a.ar_blockcount;
}

STATIC void
xfs_allocbt_trace_key(
        struct xfs_btree_cur    *cur,
        union xfs_btree_key     *key,
        __uint64_t              *l0,
        __uint64_t              *l1)
{
        *l0 = be32_to_cpu(key->alloc.ar_startblock);
        *l1 = be32_to_cpu(key->alloc.ar_blockcount);
}

STATIC void
xfs_allocbt_trace_record(
        struct xfs_btree_cur    *cur,
        union xfs_btree_rec     *rec,
        __uint64_t              *l0,
        __uint64_t              *l1,
        __uint64_t              *l2)
{
        *l0 = be32_to_cpu(rec->alloc.ar_startblock);
        *l1 = be32_to_cpu(rec->alloc.ar_blockcount);
        *l2 = 0;
}
#endif /* XFS_BTREE_TRACE */

static const struct xfs_btree_ops xfs_allocbt_ops = {
        .rec_len                = sizeof(xfs_alloc_rec_t),
        .key_len                = sizeof(xfs_alloc_key_t),

        .dup_cursor             = xfs_allocbt_dup_cursor,
        .update_lastrec         = xfs_allocbt_update_lastrec,
        .get_maxrecs            = xfs_allocbt_get_maxrecs,
        .init_key_from_rec      = xfs_allocbt_init_key_from_rec,
        .init_ptr_from_cur      = xfs_allocbt_init_ptr_from_cur,
        .key_diff               = xfs_allocbt_key_diff,

#ifdef XFS_BTREE_TRACE
        .trace_enter            = xfs_allocbt_trace_enter,
        .trace_cursor           = xfs_allocbt_trace_cursor,
        .trace_key              = xfs_allocbt_trace_key,
        .trace_record           = xfs_allocbt_trace_record,
#endif
};

/*
 * Allocate a new allocation btree cursor.
 */
struct xfs_btree_cur *                  /* new alloc btree cursor */
xfs_allocbt_init_cursor(
        struct xfs_mount        *mp,            /* file system mount point */
        struct xfs_trans        *tp,            /* transaction pointer */
        struct xfs_buf          *agbp,          /* buffer for agf structure */
        xfs_agnumber_t          agno,           /* allocation group number */
        xfs_btnum_t             btnum)          /* btree identifier */
{
        struct xfs_agf          *agf = XFS_BUF_TO_AGF(agbp);
        struct xfs_btree_cur    *cur;

        ASSERT(btnum == XFS_BTNUM_BNO || btnum == XFS_BTNUM_CNT);

        cur = kmem_zone_zalloc(xfs_btree_cur_zone, KM_SLEEP);

        cur->bc_tp = tp;
        cur->bc_mp = mp;
        cur->bc_nlevels = be32_to_cpu(agf->agf_levels[btnum]);
        cur->bc_btnum = btnum;
        cur->bc_blocklog = mp->m_sb.sb_blocklog;

        cur->bc_ops = &xfs_allocbt_ops;
        if (btnum == XFS_BTNUM_CNT)
                cur->bc_flags = XFS_BTREE_LASTREC_UPDATE;

        cur->bc_private.a.agbp = agbp;
        cur->bc_private.a.agno = agno;

        return cur;
}