/*
 * Copyright (c) 2000-2005 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_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_mount.h"
#include "xfs_da_btree.h"
#include "xfs_bmap_btree.h"
#include "xfs_dir2.h"
#include "xfs_dir2_format.h"
#include "xfs_dir2_priv.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_inode_item.h"
#include "xfs_alloc.h"
#include "xfs_bmap.h"
#include "xfs_attr.h"
#include "xfs_attr_leaf.h"
#include "xfs_error.h"
#include "xfs_trace.h"

/*
 * xfs_da_btree.c
 *
 * Routines to implement directories as Btrees of hashed names.
 */

/*========================================================================
 * Function prototypes for the kernel.
 *========================================================================*/

/*
 * Routines used for growing the Btree.
 */
STATIC int xfs_da_root_split(xfs_da_state_t *state,
                                            xfs_da_state_blk_t *existing_root,
                                            xfs_da_state_blk_t *new_child);
STATIC int xfs_da_node_split(xfs_da_state_t *state,
                                            xfs_da_state_blk_t *existing_blk,
                                            xfs_da_state_blk_t *split_blk,
                                            xfs_da_state_blk_t *blk_to_add,
                                            int treelevel,
                                            int *result);
STATIC void xfs_da_node_rebalance(xfs_da_state_t *state,
                                         xfs_da_state_blk_t *node_blk_1,
                                         xfs_da_state_blk_t *node_blk_2);
STATIC void xfs_da_node_add(xfs_da_state_t *state,
                                   xfs_da_state_blk_t *old_node_blk,
                                   xfs_da_state_blk_t *new_node_blk);

/*
 * Routines used for shrinking the Btree.
 */
STATIC int xfs_da_root_join(xfs_da_state_t *state,
                                           xfs_da_state_blk_t *root_blk);
STATIC int xfs_da_node_toosmall(xfs_da_state_t *state, int *retval);
STATIC void xfs_da_node_remove(xfs_da_state_t *state,
                                              xfs_da_state_blk_t *drop_blk);
STATIC void xfs_da_node_unbalance(xfs_da_state_t *state,
                                         xfs_da_state_blk_t *src_node_blk,
                                         xfs_da_state_blk_t *dst_node_blk);

/*
 * Utility routines.
 */
STATIC uint     xfs_da_node_lasthash(struct xfs_buf *bp, int *count);
STATIC int      xfs_da_node_order(struct xfs_buf *node1_bp,
                                  struct xfs_buf *node2_bp);
STATIC int      xfs_da_blk_unlink(xfs_da_state_t *state,
                                  xfs_da_state_blk_t *drop_blk,
                                  xfs_da_state_blk_t *save_blk);
STATIC void     xfs_da_state_kill_altpath(xfs_da_state_t *state);

/*========================================================================
 * Routines used for growing the Btree.
 *========================================================================*/

/*
 * Create the initial contents of an intermediate node.
 */
int
xfs_da_node_create(xfs_da_args_t *args, xfs_dablk_t blkno, int level,
                                 struct xfs_buf **bpp, int whichfork)
{
        xfs_da_intnode_t *node;
        struct xfs_buf *bp;
        int error;
        xfs_trans_t *tp;

        trace_xfs_da_node_create(args);

        tp = args->trans;
        error = xfs_da_get_buf(tp, args->dp, blkno, -1, &bp, whichfork);
        if (error)
                return(error);
        ASSERT(bp != NULL);
        node = bp->b_addr;
        node->hdr.info.forw = 0;
        node->hdr.info.back = 0;
        node->hdr.info.magic = cpu_to_be16(XFS_DA_NODE_MAGIC);
        node->hdr.info.pad = 0;
        node->hdr.count = 0;
        node->hdr.level = cpu_to_be16(level);

        xfs_trans_log_buf(tp, bp,
                XFS_DA_LOGRANGE(node, &node->hdr, sizeof(node->hdr)));

        *bpp = bp;
        return(0);
}

/*
 * Split a leaf node, rebalance, then possibly split
 * intermediate nodes, rebalance, etc.
 */
int                                                     /* error */
xfs_da_split(xfs_da_state_t *state)
{
        xfs_da_state_blk_t *oldblk, *newblk, *addblk;
        xfs_da_intnode_t *node;
        struct xfs_buf *bp;
        int max, action, error, i;

        trace_xfs_da_split(state->args);

        /*
         * Walk back up the tree splitting/inserting/adjusting as necessary.
         * If we need to insert and there isn't room, split the node, then
         * decide which fragment to insert the new block from below into.
         * Note that we may split the root this way, but we need more fixup.
         */
        max = state->path.active - 1;
        ASSERT((max >= 0) && (max < XFS_DA_NODE_MAXDEPTH));
        ASSERT(state->path.blk[max].magic == XFS_ATTR_LEAF_MAGIC ||
               state->path.blk[max].magic == XFS_DIR2_LEAFN_MAGIC);

        addblk = &state->path.blk[max];         /* initial dummy value */
        for (i = max; (i >= 0) && addblk; state->path.active--, i--) {
                oldblk = &state->path.blk[i];
                newblk = &state->altpath.blk[i];

                /*
                 * If a leaf node then
                 *     Allocate a new leaf node, then rebalance across them.
                 * else if an intermediate node then
                 *     We split on the last layer, must we split the node?
                 */
                switch (oldblk->magic) {
                case XFS_ATTR_LEAF_MAGIC:
                        error = xfs_attr_leaf_split(state, oldblk, newblk);
                        if ((error != 0) && (error != ENOSPC)) {
                                return(error);  /* GROT: attr is inconsistent */
                        }
                        if (!error) {
                                addblk = newblk;
                                break;
                        }
                        /*
                         * Entry wouldn't fit, split the leaf again.
                         */
                        state->extravalid = 1;
                        if (state->inleaf) {
                                state->extraafter = 0;  /* before newblk */
                                trace_xfs_attr_leaf_split_before(state->args);
                                error = xfs_attr_leaf_split(state, oldblk,
                                                            &state->extrablk);
                        } else {
                                state->extraafter = 1;  /* after newblk */
                                trace_xfs_attr_leaf_split_after(state->args);
                                error = xfs_attr_leaf_split(state, newblk,
                                                            &state->extrablk);
                        }
                        if (error)
                                return(error);  /* GROT: attr inconsistent */
                        addblk = newblk;
                        break;
                case XFS_DIR2_LEAFN_MAGIC:
                        error = xfs_dir2_leafn_split(state, oldblk, newblk);
                        if (error)
                                return error;
                        addblk = newblk;
                        break;
                case XFS_DA_NODE_MAGIC:
                        error = xfs_da_node_split(state, oldblk, newblk, addblk,
                                                         max - i, &action);
                        addblk->bp = NULL;
                        if (error)
                                return(error);  /* GROT: dir is inconsistent */
                        /*
                         * Record the newly split block for the next time thru?
                         */
                        if (action)
                                addblk = newblk;
                        else
                                addblk = NULL;
                        break;
                }

                /*
                 * Update the btree to show the new hashval for this child.
                 */
                xfs_da_fixhashpath(state, &state->path);
        }
        if (!addblk)
                return(0);

        /*
         * Split the root node.
         */
        ASSERT(state->path.active == 0);
        oldblk = &state->path.blk[0];
        error = xfs_da_root_split(state, oldblk, addblk);
        if (error) {
                addblk->bp = NULL;
                return(error);  /* GROT: dir is inconsistent */
        }

        /*
         * Update pointers to the node which used to be block 0 and
         * just got bumped because of the addition of a new root node.
         * There might be three blocks involved if a double split occurred,
         * and the original block 0 could be at any position in the list.
         */

        node = oldblk->bp->b_addr;
        if (node->hdr.info.forw) {
                if (be32_to_cpu(node->hdr.info.forw) == addblk->blkno) {
                        bp = addblk->bp;
                } else {
                        ASSERT(state->extravalid);
                        bp = state->extrablk.bp;
                }
                node = bp->b_addr;
                node->hdr.info.back = cpu_to_be32(oldblk->blkno);
                xfs_trans_log_buf(state->args->trans, bp,
                    XFS_DA_LOGRANGE(node, &node->hdr.info,
                    sizeof(node->hdr.info)));
        }
        node = oldblk->bp->b_addr;
        if (node->hdr.info.back) {
                if (be32_to_cpu(node->hdr.info.back) == addblk->blkno) {
                        bp = addblk->bp;
                } else {
                        ASSERT(state->extravalid);
                        bp = state->extrablk.bp;
                }
                node = bp->b_addr;
                node->hdr.info.forw = cpu_to_be32(oldblk->blkno);
                xfs_trans_log_buf(state->args->trans, bp,
                    XFS_DA_LOGRANGE(node, &node->hdr.info,
                    sizeof(node->hdr.info)));
        }
        addblk->bp = NULL;
        return(0);
}

/*
 * Split the root.  We have to create a new root and point to the two
 * parts (the split old root) that we just created.  Copy block zero to
 * the EOF, extending the inode in process.
 */
STATIC int                                              /* error */
xfs_da_root_split(xfs_da_state_t *state, xfs_da_state_blk_t *blk1,
                                 xfs_da_state_blk_t *blk2)
{
        xfs_da_intnode_t *node, *oldroot;
        xfs_da_args_t *args;
        xfs_dablk_t blkno;
        struct xfs_buf *bp;
        int error, size;
        xfs_inode_t *dp;
        xfs_trans_t *tp;
        xfs_mount_t *mp;
        xfs_dir2_leaf_t *leaf;

        trace_xfs_da_root_split(state->args);

        /*
         * Copy the existing (incorrect) block from the root node position
         * to a free space somewhere.
         */
        args = state->args;
        ASSERT(args != NULL);
        error = xfs_da_grow_inode(args, &blkno);
        if (error)
                return(error);
        dp = args->dp;
        tp = args->trans;
        mp = state->mp;
        error = xfs_da_get_buf(tp, dp, blkno, -1, &bp, args->whichfork);
        if (error)
                return(error);
        ASSERT(bp != NULL);
        node = bp->b_addr;
        oldroot = blk1->bp->b_addr;
        if (oldroot->hdr.info.magic == cpu_to_be16(XFS_DA_NODE_MAGIC)) {
                size = (int)((char *)&oldroot->btree[be16_to_cpu(oldroot->hdr.count)] -
                             (char *)oldroot);
        } else {
                ASSERT(oldroot->hdr.info.magic == cpu_to_be16(XFS_DIR2_LEAFN_MAGIC));
                leaf = (xfs_dir2_leaf_t *)oldroot;
                size = (int)((char *)&leaf->ents[be16_to_cpu(leaf->hdr.count)] -
                             (char *)leaf);
        }
        memcpy(node, oldroot, size);
        xfs_trans_log_buf(tp, bp, 0, size - 1);
        blk1->bp = bp;
        blk1->blkno = blkno;

        /*
         * Set up the new root node.
         */
        error = xfs_da_node_create(args,
                (args->whichfork == XFS_DATA_FORK) ? mp->m_dirleafblk : 0,
                be16_to_cpu(node->hdr.level) + 1, &bp, args->whichfork);
        if (error)
                return(error);
        node = bp->b_addr;
        node->btree[0].hashval = cpu_to_be32(blk1->hashval);
        node->btree[0].before = cpu_to_be32(blk1->blkno);
        node->btree[1].hashval = cpu_to_be32(blk2->hashval);
        node->btree[1].before = cpu_to_be32(blk2->blkno);
        node->hdr.count = cpu_to_be16(2);

#ifdef DEBUG
        if (oldroot->hdr.info.magic == cpu_to_be16(XFS_DIR2_LEAFN_MAGIC)) {
                ASSERT(blk1->blkno >= mp->m_dirleafblk &&
                       blk1->blkno < mp->m_dirfreeblk);
                ASSERT(blk2->blkno >= mp->m_dirleafblk &&
                       blk2->blkno < mp->m_dirfreeblk);
        }
#endif

        /* Header is already logged by xfs_da_node_create */
        xfs_trans_log_buf(tp, bp,
                XFS_DA_LOGRANGE(node, node->btree,
                        sizeof(xfs_da_node_entry_t) * 2));

        return(0);
}

/*
 * Split the node, rebalance, then add the new entry.
 */
STATIC int                                              /* error */
xfs_da_node_split(xfs_da_state_t *state, xfs_da_state_blk_t *oldblk,
                                 xfs_da_state_blk_t *newblk,
                                 xfs_da_state_blk_t *addblk,
                                 int treelevel, int *result)
{
        xfs_da_intnode_t *node;
        xfs_dablk_t blkno;
        int newcount, error;
        int useextra;

        trace_xfs_da_node_split(state->args);

        node = oldblk->bp->b_addr;
        ASSERT(node->hdr.info.magic == cpu_to_be16(XFS_DA_NODE_MAGIC));

        /*
         * With V2 dirs the extra block is data or freespace.
         */
        useextra = state->extravalid && state->args->whichfork == XFS_ATTR_FORK;
        newcount = 1 + useextra;
        /*
         * Do we have to split the node?
         */
        if ((be16_to_cpu(node->hdr.count) + newcount) > state->node_ents) {
                /*
                 * Allocate a new node, add to the doubly linked chain of
                 * nodes, then move some of our excess entries into it.
                 */
                error = xfs_da_grow_inode(state->args, &blkno);
                if (error)
                        return(error);  /* GROT: dir is inconsistent */

                error = xfs_da_node_create(state->args, blkno, treelevel,
                                           &newblk->bp, state->args->whichfork);
                if (error)
                        return(error);  /* GROT: dir is inconsistent */
                newblk->blkno = blkno;
                newblk->magic = XFS_DA_NODE_MAGIC;
                xfs_da_node_rebalance(state, oldblk, newblk);
                error = xfs_da_blk_link(state, oldblk, newblk);
                if (error)
                        return(error);
                *result = 1;
        } else {
                *result = 0;
        }

        /*
         * Insert the new entry(s) into the correct block
         * (updating last hashval in the process).
         *
         * xfs_da_node_add() inserts BEFORE the given index,
         * and as a result of using node_lookup_int() we always
         * point to a valid entry (not after one), but a split
         * operation always results in a new block whose hashvals
         * FOLLOW the current block.
         *
         * If we had double-split op below us, then add the extra block too.
         */
        node = oldblk->bp->b_addr;
        if (oldblk->index <= be16_to_cpu(node->hdr.count)) {
                oldblk->index++;
                xfs_da_node_add(state, oldblk, addblk);
                if (useextra) {
                        if (state->extraafter)
                                oldblk->index++;
                        xfs_da_node_add(state, oldblk, &state->extrablk);
                        state->extravalid = 0;
                }
        } else {
                newblk->index++;
                xfs_da_node_add(state, newblk, addblk);
                if (useextra) {
                        if (state->extraafter)
                                newblk->index++;
                        xfs_da_node_add(state, newblk, &state->extrablk);
                        state->extravalid = 0;
                }
        }

        return(0);
}

/*
 * Balance the btree elements between two intermediate nodes,
 * usually one full and one empty.
 *
 * NOTE: if blk2 is empty, then it will get the upper half of blk1.
 */
STATIC void
xfs_da_node_rebalance(xfs_da_state_t *state, xfs_da_state_blk_t *blk1,
                                     xfs_da_state_blk_t *blk2)
{
        xfs_da_intnode_t *node1, *node2, *tmpnode;
        xfs_da_node_entry_t *btree_s, *btree_d;
        int count, tmp;
        xfs_trans_t *tp;

        trace_xfs_da_node_rebalance(state->args);

        node1 = blk1->bp->b_addr;
        node2 = blk2->bp->b_addr;
        /*
         * Figure out how many entries need to move, and in which direction.
         * Swap the nodes around if that makes it simpler.
         */
        if ((be16_to_cpu(node1->hdr.count) > 0) && (be16_to_cpu(node2->hdr.count) > 0) &&
            ((be32_to_cpu(node2->btree[0].hashval) < be32_to_cpu(node1->btree[0].hashval)) ||
             (be32_to_cpu(node2->btree[be16_to_cpu(node2->hdr.count)-1].hashval) <
              be32_to_cpu(node1->btree[be16_to_cpu(node1->hdr.count)-1].hashval)))) {
                tmpnode = node1;
                node1 = node2;
                node2 = tmpnode;
        }
        ASSERT(node1->hdr.info.magic == cpu_to_be16(XFS_DA_NODE_MAGIC));
        ASSERT(node2->hdr.info.magic == cpu_to_be16(XFS_DA_NODE_MAGIC));
        count = (be16_to_cpu(node1->hdr.count) - be16_to_cpu(node2->hdr.count)) / 2;
        if (count == 0)
                return;
        tp = state->args->trans;
        /*
         * Two cases: high-to-low and low-to-high.
         */
        if (count > 0) {
                /*
                 * Move elements in node2 up to make a hole.
                 */
                if ((tmp = be16_to_cpu(node2->hdr.count)) > 0) {
                        tmp *= (uint)sizeof(xfs_da_node_entry_t);
                        btree_s = &node2->btree[0];
                        btree_d = &node2->btree[count];
                        memmove(btree_d, btree_s, tmp);
                }

                /*
                 * Move the req'd B-tree elements from high in node1 to
                 * low in node2.
                 */
                be16_add_cpu(&node2->hdr.count, count);
                tmp = count * (uint)sizeof(xfs_da_node_entry_t);
                btree_s = &node1->btree[be16_to_cpu(node1->hdr.count) - count];
                btree_d = &node2->btree[0];
                memcpy(btree_d, btree_s, tmp);
                be16_add_cpu(&node1->hdr.count, -count);
        } else {
                /*
                 * Move the req'd B-tree elements from low in node2 to
                 * high in node1.
                 */
                count = -count;
                tmp = count * (uint)sizeof(xfs_da_node_entry_t);
                btree_s = &node2->btree[0];
                btree_d = &node1->btree[be16_to_cpu(node1->hdr.count)];
                memcpy(btree_d, btree_s, tmp);
                be16_add_cpu(&node1->hdr.count, count);
                xfs_trans_log_buf(tp, blk1->bp,
                        XFS_DA_LOGRANGE(node1, btree_d, tmp));

                /*
                 * Move elements in node2 down to fill the hole.
                 */
                tmp  = be16_to_cpu(node2->hdr.count) - count;
                tmp *= (uint)sizeof(xfs_da_node_entry_t);
                btree_s = &node2->btree[count];
                btree_d = &node2->btree[0];
                memmove(btree_d, btree_s, tmp);
                be16_add_cpu(&node2->hdr.count, -count);
        }

        /*
         * Log header of node 1 and all current bits of node 2.
         */
        xfs_trans_log_buf(tp, blk1->bp,
                XFS_DA_LOGRANGE(node1, &node1->hdr, sizeof(node1->hdr)));
        xfs_trans_log_buf(tp, blk2->bp,
                XFS_DA_LOGRANGE(node2, &node2->hdr,
                        sizeof(node2->hdr) +
                        sizeof(node2->btree[0]) * be16_to_cpu(node2->hdr.count)));

        /*
         * Record the last hashval from each block for upward propagation.
         * (note: don't use the swapped node pointers)
         */
        node1 = blk1->bp->b_addr;
        node2 = blk2->bp->b_addr;
        blk1->hashval = be32_to_cpu(node1->btree[be16_to_cpu(node1->hdr.count)-1].hashval);
        blk2->hashval = be32_to_cpu(node2->btree[be16_to_cpu(node2->hdr.count)-1].hashval);

        /*
         * Adjust the expected index for insertion.
         */
        if (blk1->index >= be16_to_cpu(node1->hdr.count)) {
                blk2->index = blk1->index - be16_to_cpu(node1->hdr.count);
                blk1->index = be16_to_cpu(node1->hdr.count) + 1;        /* make it invalid */
        }
}

/*
 * Add a new entry to an intermediate node.
 */
STATIC void
xfs_da_node_add(xfs_da_state_t *state, xfs_da_state_blk_t *oldblk,
                               xfs_da_state_blk_t *newblk)
{
        xfs_da_intnode_t *node;
        xfs_da_node_entry_t *btree;
        int tmp;

        trace_xfs_da_node_add(state->args);

        node = oldblk->bp->b_addr;
        ASSERT(node->hdr.info.magic == cpu_to_be16(XFS_DA_NODE_MAGIC));
        ASSERT((oldblk->index >= 0) && (oldblk->index <= be16_to_cpu(node->hdr.count)));
        ASSERT(newblk->blkno != 0);
        if (state->args->whichfork == XFS_DATA_FORK)
                ASSERT(newblk->blkno >= state->mp->m_dirleafblk &&
                       newblk->blkno < state->mp->m_dirfreeblk);

        /*
         * We may need to make some room before we insert the new node.
         */
        tmp = 0;
        btree = &node->btree[ oldblk->index ];
        if (oldblk->index < be16_to_cpu(node->hdr.count)) {
                tmp = (be16_to_cpu(node->hdr.count) - oldblk->index) * (uint)sizeof(*btree);
                memmove(btree + 1, btree, tmp);
        }
        btree->hashval = cpu_to_be32(newblk->hashval);
        btree->before = cpu_to_be32(newblk->blkno);
        xfs_trans_log_buf(state->args->trans, oldblk->bp,
                XFS_DA_LOGRANGE(node, btree, tmp + sizeof(*btree)));
        be16_add_cpu(&node->hdr.count, 1);
        xfs_trans_log_buf(state->args->trans, oldblk->bp,
                XFS_DA_LOGRANGE(node, &node->hdr, sizeof(node->hdr)));

        /*
         * Copy the last hash value from the oldblk to propagate upwards.
         */
        oldblk->hashval = be32_to_cpu(node->btree[be16_to_cpu(node->hdr.count)-1 ].hashval);
}

/*========================================================================
 * Routines used for shrinking the Btree.
 *========================================================================*/

/*
 * Deallocate an empty leaf node, remove it from its parent,
 * possibly deallocating that block, etc...
 */
int
xfs_da_join(xfs_da_state_t *state)
{
        xfs_da_state_blk_t *drop_blk, *save_blk;
        int action, error;

        trace_xfs_da_join(state->args);

        action = 0;
        drop_blk = &state->path.blk[ state->path.active-1 ];
        save_blk = &state->altpath.blk[ state->path.active-1 ];
        ASSERT(state->path.blk[0].magic == XFS_DA_NODE_MAGIC);
        ASSERT(drop_blk->magic == XFS_ATTR_LEAF_MAGIC ||
               drop_blk->magic == XFS_DIR2_LEAFN_MAGIC);

        /*
         * Walk back up the tree joining/deallocating as necessary.
         * When we stop dropping blocks, break out.
         */
        for (  ; state->path.active >= 2; drop_blk--, save_blk--,
                 state->path.active--) {
                /*
                 * See if we can combine the block with a neighbor.
                 *   (action == 0) => no options, just leave
                 *   (action == 1) => coalesce, then unlink
                 *   (action == 2) => block empty, unlink it
                 */
                switch (drop_blk->magic) {
                case XFS_ATTR_LEAF_MAGIC:
                        error = xfs_attr_leaf_toosmall(state, &action);
                        if (error)
                                return(error);
                        if (action == 0)
                                return(0);
                        xfs_attr_leaf_unbalance(state, drop_blk, save_blk);
                        break;
                case XFS_DIR2_LEAFN_MAGIC:
                        error = xfs_dir2_leafn_toosmall(state, &action);
                        if (error)
                                return error;
                        if (action == 0)
                                return 0;
                        xfs_dir2_leafn_unbalance(state, drop_blk, save_blk);
                        break;
                case XFS_DA_NODE_MAGIC:
                        /*
                         * Remove the offending node, fixup hashvals,
                         * check for a toosmall neighbor.
                         */
                        xfs_da_node_remove(state, drop_blk);
                        xfs_da_fixhashpath(state, &state->path);
                        error = xfs_da_node_toosmall(state, &action);
                        if (error)
                                return(error);
                        if (action == 0)
                                return 0;
                        xfs_da_node_unbalance(state, drop_blk, save_blk);
                        break;
                }
                xfs_da_fixhashpath(state, &state->altpath);
                error = xfs_da_blk_unlink(state, drop_blk, save_blk);
                xfs_da_state_kill_altpath(state);
                if (error)
                        return(error);
                error = xfs_da_shrink_inode(state->args, drop_blk->blkno,
                                                         drop_blk->bp);
                drop_blk->bp = NULL;
                if (error)
                        return(error);
        }
        /*
         * We joined all the way to the top.  If it turns out that
         * we only have one entry in the root, make the child block
         * the new root.
         */
        xfs_da_node_remove(state, drop_blk);
        xfs_da_fixhashpath(state, &state->path);
        error = xfs_da_root_join(state, &state->path.blk[0]);
        return(error);
}

#ifdef  DEBUG
static void
xfs_da_blkinfo_onlychild_validate(struct xfs_da_blkinfo *blkinfo, __u16 level)
{
        __be16  magic = blkinfo->magic;

        if (level == 1) {
                ASSERT(magic == cpu_to_be16(XFS_DIR2_LEAFN_MAGIC) ||
                       magic == cpu_to_be16(XFS_ATTR_LEAF_MAGIC));
        } else
                ASSERT(magic == cpu_to_be16(XFS_DA_NODE_MAGIC));
        ASSERT(!blkinfo->forw);
        ASSERT(!blkinfo->back);
}
#else   /* !DEBUG */
#define xfs_da_blkinfo_onlychild_validate(blkinfo, level)
#endif  /* !DEBUG */

/*
 * We have only one entry in the root.  Copy the only remaining child of
 * the old root to block 0 as the new root node.
 */
STATIC int
xfs_da_root_join(xfs_da_state_t *state, xfs_da_state_blk_t *root_blk)
{
        xfs_da_intnode_t *oldroot;
        xfs_da_args_t *args;
        xfs_dablk_t child;
        struct xfs_buf *bp;
        int error;

        trace_xfs_da_root_join(state->args);

        args = state->args;
        ASSERT(args != NULL);
        ASSERT(root_blk->magic == XFS_DA_NODE_MAGIC);
        oldroot = root_blk->bp->b_addr;
        ASSERT(oldroot->hdr.info.magic == cpu_to_be16(XFS_DA_NODE_MAGIC));
        ASSERT(!oldroot->hdr.info.forw);
        ASSERT(!oldroot->hdr.info.back);

        /*
         * If the root has more than one child, then don't do anything.
         */
        if (be16_to_cpu(oldroot->hdr.count) > 1)
                return(0);

        /*
         * Read in the (only) child block, then copy those bytes into
         * the root block's buffer and free the original child block.
         */
        child = be32_to_cpu(oldroot->btree[0].before);
        ASSERT(child != 0);
        error = xfs_da_read_buf(args->trans, args->dp, child, -1, &bp,
                                             args->whichfork);
        if (error)
                return(error);
        ASSERT(bp != NULL);
        xfs_da_blkinfo_onlychild_validate(bp->b_addr,
                                        be16_to_cpu(oldroot->hdr.level));

        memcpy(root_blk->bp->b_addr, bp->b_addr, state->blocksize);
        xfs_trans_log_buf(args->trans, root_blk->bp, 0, state->blocksize - 1);
        error = xfs_da_shrink_inode(args, child, bp);
        return(error);
}

/*
 * Check a node block and its neighbors to see if the block should be
 * collapsed into one or the other neighbor.  Always keep the block
 * with the smaller block number.
 * If the current block is over 50% full, don't try to join it, return 0.
 * If the block is empty, fill in the state structure and return 2.
 * If it can be collapsed, fill in the state structure and return 1.
 * If nothing can be done, return 0.
 */
STATIC int
xfs_da_node_toosmall(xfs_da_state_t *state, int *action)
{
        xfs_da_intnode_t *node;
        xfs_da_state_blk_t *blk;
        xfs_da_blkinfo_t *info;
        int count, forward, error, retval, i;
        xfs_dablk_t blkno;
        struct xfs_buf *bp;

        /*
         * Check for the degenerate case of the block being over 50% full.
         * If so, it's not worth even looking to see if we might be able
         * to coalesce with a sibling.
         */
        blk = &state->path.blk[ state->path.active-1 ];
        info = blk->bp->b_addr;
        ASSERT(info->magic == cpu_to_be16(XFS_DA_NODE_MAGIC));
        node = (xfs_da_intnode_t *)info;
        count = be16_to_cpu(node->hdr.count);
        if (count > (state->node_ents >> 1)) {
                *action = 0;    /* blk over 50%, don't try to join */
                return(0);      /* blk over 50%, don't try to join */
        }

        /*
         * Check for the degenerate case of the block being empty.
         * If the block is empty, we'll simply delete it, no need to
         * coalesce it with a sibling block.  We choose (arbitrarily)
         * to merge with the forward block unless it is NULL.
         */
        if (count == 0) {
                /*
                 * Make altpath point to the block we want to keep and
                 * path point to the block we want to drop (this one).
                 */
                forward = (info->forw != 0);
                memcpy(&state->altpath, &state->path, sizeof(state->path));
                error = xfs_da_path_shift(state, &state->altpath, forward,
                                                 0, &retval);
                if (error)
                        return(error);
                if (retval) {
                        *action = 0;
                } else {
                        *action = 2;
                }
                return(0);
        }

        /*
         * Examine each sibling block to see if we can coalesce with
         * at least 25% free space to spare.  We need to figure out
         * whether to merge with the forward or the backward block.
         * We prefer coalescing with the lower numbered sibling so as
         * to shrink a directory over time.
         */
        /* start with smaller blk num */
        forward = (be32_to_cpu(info->forw) < be32_to_cpu(info->back));
        for (i = 0; i < 2; forward = !forward, i++) {
                if (forward)
                        blkno = be32_to_cpu(info->forw);
                else
                        blkno = be32_to_cpu(info->back);
                if (blkno == 0)
                        continue;
                error = xfs_da_read_buf(state->args->trans, state->args->dp,
                                        blkno, -1, &bp, state->args->whichfork);
                if (error)
                        return(error);
                ASSERT(bp != NULL);

                node = (xfs_da_intnode_t *)info;
                count  = state->node_ents;
                count -= state->node_ents >> 2;
                count -= be16_to_cpu(node->hdr.count);
                node = bp->b_addr;
                ASSERT(node->hdr.info.magic == cpu_to_be16(XFS_DA_NODE_MAGIC));
                count -= be16_to_cpu(node->hdr.count);
                xfs_trans_brelse(state->args->trans, bp);
                if (count >= 0)
                        break;  /* fits with at least 25% to spare */
        }
        if (i >= 2) {
                *action = 0;
                return(0);
        }

        /*
         * Make altpath point to the block we want to keep (the lower
         * numbered block) and path point to the block we want to drop.
         */
        memcpy(&state->altpath, &state->path, sizeof(state->path));
        if (blkno < blk->blkno) {
                error = xfs_da_path_shift(state, &state->altpath, forward,
                                                 0, &retval);
                if (error) {
                        return(error);
                }
                if (retval) {
                        *action = 0;
                        return(0);
                }
        } else {
                error = xfs_da_path_shift(state, &state->path, forward,
                                                 0, &retval);
                if (error) {
                        return(error);
                }
                if (retval) {
                        *action = 0;
                        return(0);
                }
        }
        *action = 1;
        return(0);
}

/*
 * Walk back up the tree adjusting hash values as necessary,
 * when we stop making changes, return.
 */
void
xfs_da_fixhashpath(xfs_da_state_t *state, xfs_da_state_path_t *path)
{
        xfs_da_state_blk_t *blk;
        xfs_da_intnode_t *node;
        xfs_da_node_entry_t *btree;
        xfs_dahash_t lasthash=0;
        int level, count;

        level = path->active-1;
        blk = &path->blk[ level ];
        switch (blk->magic) {
        case XFS_ATTR_LEAF_MAGIC:
                lasthash = xfs_attr_leaf_lasthash(blk->bp, &count);
                if (count == 0)
                        return;
                break;
        case XFS_DIR2_LEAFN_MAGIC:
                lasthash = xfs_dir2_leafn_lasthash(blk->bp, &count);
                if (count == 0)
                        return;
                break;
        case XFS_DA_NODE_MAGIC:
                lasthash = xfs_da_node_lasthash(blk->bp, &count);
                if (count == 0)
                        return;
                break;
        }
        for (blk--, level--; level >= 0; blk--, level--) {
                node = blk->bp->b_addr;
                ASSERT(node->hdr.info.magic == cpu_to_be16(XFS_DA_NODE_MAGIC));
                btree = &node->btree[ blk->index ];
                if (be32_to_cpu(btree->hashval) == lasthash)
                        break;
                blk->hashval = lasthash;
                btree->hashval = cpu_to_be32(lasthash);
                xfs_trans_log_buf(state->args->trans, blk->bp,
                                  XFS_DA_LOGRANGE(node, btree, sizeof(*btree)));

                lasthash = be32_to_cpu(node->btree[be16_to_cpu(node->hdr.count)-1].hashval);
        }
}

/*
 * Remove an entry from an intermediate node.
 */
STATIC void
xfs_da_node_remove(xfs_da_state_t *state, xfs_da_state_blk_t *drop_blk)
{
        xfs_da_intnode_t *node;
        xfs_da_node_entry_t *btree;
        int tmp;

        trace_xfs_da_node_remove(state->args);

        node = drop_blk->bp->b_addr;
        ASSERT(drop_blk->index < be16_to_cpu(node->hdr.count));
        ASSERT(drop_blk->index >= 0);

        /*
         * Copy over the offending entry, or just zero it out.
         */
        btree = &node->btree[drop_blk->index];
        if (drop_blk->index < (be16_to_cpu(node->hdr.count)-1)) {
                tmp  = be16_to_cpu(node->hdr.count) - drop_blk->index - 1;
                tmp *= (uint)sizeof(xfs_da_node_entry_t);
                memmove(btree, btree + 1, tmp);
                xfs_trans_log_buf(state->args->trans, drop_blk->bp,
                    XFS_DA_LOGRANGE(node, btree, tmp));
                btree = &node->btree[be16_to_cpu(node->hdr.count)-1];
        }
        memset((char *)btree, 0, sizeof(xfs_da_node_entry_t));
        xfs_trans_log_buf(state->args->trans, drop_blk->bp,
            XFS_DA_LOGRANGE(node, btree, sizeof(*btree)));
        be16_add_cpu(&node->hdr.count, -1);
        xfs_trans_log_buf(state->args->trans, drop_blk->bp,
            XFS_DA_LOGRANGE(node, &node->hdr, sizeof(node->hdr)));

        /*
         * Copy the last hash value from the block to propagate upwards.
         */
        btree--;
        drop_blk->hashval = be32_to_cpu(btree->hashval);
}

/*
 * Unbalance the btree elements between two intermediate nodes,
 * move all Btree elements from one node into another.
 */
STATIC void
xfs_da_node_unbalance(xfs_da_state_t *state, xfs_da_state_blk_t *drop_blk,
                                     xfs_da_state_blk_t *save_blk)
{
        xfs_da_intnode_t *drop_node, *save_node;
        xfs_da_node_entry_t *btree;
        int tmp;
        xfs_trans_t *tp;

        trace_xfs_da_node_unbalance(state->args);

        drop_node = drop_blk->bp->b_addr;
        save_node = save_blk->bp->b_addr;
        ASSERT(drop_node->hdr.info.magic == cpu_to_be16(XFS_DA_NODE_MAGIC));
        ASSERT(save_node->hdr.info.magic == cpu_to_be16(XFS_DA_NODE_MAGIC));
        tp = state->args->trans;

        /*

         * If the dying block has lower hashvals, then move all the
         * elements in the remaining block up to make a hole.
         */
        if ((be32_to_cpu(drop_node->btree[0].hashval) < be32_to_cpu(save_node->btree[ 0 ].hashval)) ||
            (be32_to_cpu(drop_node->btree[be16_to_cpu(drop_node->hdr.count)-1].hashval) <
             be32_to_cpu(save_node->btree[be16_to_cpu(save_node->hdr.count)-1].hashval)))
        {
                btree = &save_node->btree[be16_to_cpu(drop_node->hdr.count)];
                tmp = be16_to_cpu(save_node->hdr.count) * (uint)sizeof(xfs_da_node_entry_t);
                memmove(btree, &save_node->btree[0], tmp);
                btree = &save_node->btree[0];
                xfs_trans_log_buf(tp, save_blk->bp,
                        XFS_DA_LOGRANGE(save_node, btree,
                                (be16_to_cpu(save_node->hdr.count) + be16_to_cpu(drop_node->hdr.count)) *
                                sizeof(xfs_da_node_entry_t)));
        } else {
                btree = &save_node->btree[be16_to_cpu(save_node->hdr.count)];
                xfs_trans_log_buf(tp, save_blk->bp,
                        XFS_DA_LOGRANGE(save_node, btree,
                                be16_to_cpu(drop_node->hdr.count) *
                                sizeof(xfs_da_node_entry_t)));
        }

        /*
         * Move all the B-tree elements from drop_blk to save_blk.
         */
        tmp = be16_to_cpu(drop_node->hdr.count) * (uint)sizeof(xfs_da_node_entry_t);
        memcpy(btree, &drop_node->btree[0], tmp);
        be16_add_cpu(&save_node->hdr.count, be16_to_cpu(drop_node->hdr.count));

        xfs_trans_log_buf(tp, save_blk->bp,
                XFS_DA_LOGRANGE(save_node, &save_node->hdr,
                        sizeof(save_node->hdr)));

        /*
         * Save the last hashval in the remaining block for upward propagation.
         */
        save_blk->hashval = be32_to_cpu(save_node->btree[be16_to_cpu(save_node->hdr.count)-1].hashval);
}

/*========================================================================
 * Routines used for finding things in the Btree.
 *========================================================================*/

/*
 * Walk down the Btree looking for a particular filename, filling
 * in the state structure as we go.
 *
 * We will set the state structure to point to each of the elements
 * in each of the nodes where either the hashval is or should be.
 *
 * We support duplicate hashval's so for each entry in the current
 * node that could contain the desired hashval, descend.  This is a
 * pruned depth-first tree search.
 */
int                                                     /* error */
xfs_da_node_lookup_int(xfs_da_state_t *state, int *result)
{
        xfs_da_state_blk_t *blk;
        xfs_da_blkinfo_t *curr;
        xfs_da_intnode_t *node;
        xfs_da_node_entry_t *btree;
        xfs_dablk_t blkno;
        int probe, span, max, error, retval;
        xfs_dahash_t hashval, btreehashval;
        xfs_da_args_t *args;

        args = state->args;

        /*
         * Descend thru the B-tree searching each level for the right
         * node to use, until the right hashval is found.
         */
        blkno = (args->whichfork == XFS_DATA_FORK)? state->mp->m_dirleafblk : 0;
        for (blk = &state->path.blk[0], state->path.active = 1;
                         state->path.active <= XFS_DA_NODE_MAXDEPTH;
                         blk++, state->path.active++) {
                /*
                 * Read the next node down in the tree.
                 */
                blk->blkno = blkno;
                error = xfs_da_read_buf(args->trans, args->dp, blkno,
                                        -1, &blk->bp, args->whichfork);
                if (error) {
                        blk->blkno = 0;
                        state->path.active--;
                        return(error);
                }
                curr = blk->bp->b_addr;
                blk->magic = be16_to_cpu(curr->magic);
                ASSERT(blk->magic == XFS_DA_NODE_MAGIC ||
                       blk->magic == XFS_DIR2_LEAFN_MAGIC ||
                       blk->magic == XFS_ATTR_LEAF_MAGIC);

                /*
                 * Search an intermediate node for a match.
                 */
                if (blk->magic == XFS_DA_NODE_MAGIC) {
                        node = blk->bp->b_addr;
                        max = be16_to_cpu(node->hdr.count);
                        blk->hashval = be32_to_cpu(node->btree[max-1].hashval);

                        /*
                         * Binary search.  (note: small blocks will skip loop)
                         */
                        probe = span = max / 2;
                        hashval = args->hashval;
                        for (btree = &node->btree[probe]; span > 4;
                                   btree = &node->btree[probe]) {
                                span /= 2;
                                btreehashval = be32_to_cpu(btree->hashval);
                                if (btreehashval < hashval)
                                        probe += span;
                                else if (btreehashval > hashval)
                                        probe -= span;
                                else
                                        break;
                        }
                        ASSERT((probe >= 0) && (probe < max));
                        ASSERT((span <= 4) || (be32_to_cpu(btree->hashval) == hashval));

                        /*
                         * Since we may have duplicate hashval's, find the first
                         * matching hashval in the node.
                         */
                        while ((probe > 0) && (be32_to_cpu(btree->hashval) >= hashval)) {
                                btree--;
                                probe--;
                        }
                        while ((probe < max) && (be32_to_cpu(btree->hashval) < hashval)) {
                                btree++;
                                probe++;
                        }

                        /*
                         * Pick the right block to descend on.
                         */
                        if (probe == max) {
                                blk->index = max-1;
                                blkno = be32_to_cpu(node->btree[max-1].before);
                        } else {
                                blk->index = probe;
                                blkno = be32_to_cpu(btree->before);
                        }
                } else if (blk->magic == XFS_ATTR_LEAF_MAGIC) {
                        blk->hashval = xfs_attr_leaf_lasthash(blk->bp, NULL);
                        break;
                } else if (blk->magic == XFS_DIR2_LEAFN_MAGIC) {
                        blk->hashval = xfs_dir2_leafn_lasthash(blk->bp, NULL);
                        break;
                }
        }

        /*
         * A leaf block that ends in the hashval that we are interested in
         * (final hashval == search hashval) means that the next block may
         * contain more entries with the same hashval, shift upward to the
         * next leaf and keep searching.
         */
        for (;;) {
                if (blk->magic == XFS_DIR2_LEAFN_MAGIC) {
                        retval = xfs_dir2_leafn_lookup_int(blk->bp, args,
                                                        &blk->index, state);
                } else if (blk->magic == XFS_ATTR_LEAF_MAGIC) {
                        retval = xfs_attr_leaf_lookup_int(blk->bp, args);
                        blk->index = args->index;
                        args->blkno = blk->blkno;
                } else {
                        ASSERT(0);
                        return XFS_ERROR(EFSCORRUPTED);
                }
                if (((retval == ENOENT) || (retval == ENOATTR)) &&
                    (blk->hashval == args->hashval)) {
                        error = xfs_da_path_shift(state, &state->path, 1, 1,
                                                         &retval);
                        if (error)
                                return(error);
                        if (retval == 0) {
                                continue;
                        } else if (blk->magic == XFS_ATTR_LEAF_MAGIC) {
                                /* path_shift() gives ENOENT */
                                retval = XFS_ERROR(ENOATTR);
                        }
                }
                break;
        }
        *result = retval;
        return(0);
}

/*========================================================================
 * Utility routines.
 *========================================================================*/

/*
 * Link a new block into a doubly linked list of blocks (of whatever type).
 */
int                                                     /* error */
xfs_da_blk_link(xfs_da_state_t *state, xfs_da_state_blk_t *old_blk,
                               xfs_da_state_blk_t *new_blk)
{
        xfs_da_blkinfo_t *old_info, *new_info, *tmp_info;
        xfs_da_args_t *args;
        int before=0, error;
        struct xfs_buf *bp;

        /*
         * Set up environment.
         */
        args = state->args;
        ASSERT(args != NULL);
        old_info = old_blk->bp->b_addr;
        new_info = new_blk->bp->b_addr;
        ASSERT(old_blk->magic == XFS_DA_NODE_MAGIC ||
               old_blk->magic == XFS_DIR2_LEAFN_MAGIC ||
               old_blk->magic == XFS_ATTR_LEAF_MAGIC);
        ASSERT(old_blk->magic == be16_to_cpu(old_info->magic));
        ASSERT(new_blk->magic == be16_to_cpu(new_info->magic));
        ASSERT(old_blk->magic == new_blk->magic);

        switch (old_blk->magic) {
        case XFS_ATTR_LEAF_MAGIC:
                before = xfs_attr_leaf_order(old_blk->bp, new_blk->bp);
                break;
        case XFS_DIR2_LEAFN_MAGIC:
                before = xfs_dir2_leafn_order(old_blk->bp, new_blk->bp);
                break;
        case XFS_DA_NODE_MAGIC:
                before = xfs_da_node_order(old_blk->bp, new_blk->bp);
                break;
        }

        /*
         * Link blocks in appropriate order.
         */
        if (before) {
                /*
                 * Link new block in before existing block.
                 */
                trace_xfs_da_link_before(args);
                new_info->forw = cpu_to_be32(old_blk->blkno);
                new_info->back = old_info->back;
                if (old_info->back) {
                        error = xfs_da_read_buf(args->trans, args->dp,
                                                be32_to_cpu(old_info->back),
                                                -1, &bp, args->whichfork);
                        if (error)
                                return(error);
                        ASSERT(bp != NULL);
                        tmp_info = bp->b_addr;
                        ASSERT(be16_to_cpu(tmp_info->magic) == be16_to_cpu(old_info->magic));
                        ASSERT(be32_to_cpu(tmp_info->forw) == old_blk->blkno);
                        tmp_info->forw = cpu_to_be32(new_blk->blkno);
                        xfs_trans_log_buf(args->trans, bp, 0, sizeof(*tmp_info)-1);
                }
                old_info->back = cpu_to_be32(new_blk->blkno);
        } else {
                /*
                 * Link new block in after existing block.
                 */
                trace_xfs_da_link_after(args);
                new_info->forw = old_info->forw;
                new_info->back = cpu_to_be32(old_blk->blkno);
                if (old_info->forw) {
                        error = xfs_da_read_buf(args->trans, args->dp,
                                                be32_to_cpu(old_info->forw),
                                                -1, &bp, args->whichfork);
                        if (error)
                                return(error);
                        ASSERT(bp != NULL);
                        tmp_info = bp->b_addr;
                        ASSERT(tmp_info->magic == old_info->magic);
                        ASSERT(be32_to_cpu(tmp_info->back) == old_blk->blkno);
                        tmp_info->back = cpu_to_be32(new_blk->blkno);
                        xfs_trans_log_buf(args->trans, bp, 0, sizeof(*tmp_info)-1);
                }
                old_info->forw = cpu_to_be32(new_blk->blkno);
        }

        xfs_trans_log_buf(args->trans, old_blk->bp, 0, sizeof(*tmp_info) - 1);
        xfs_trans_log_buf(args->trans, new_blk->bp, 0, sizeof(*tmp_info) - 1);
        return(0);
}

/*
 * Compare two intermediate nodes for "order".
 */
STATIC int
xfs_da_node_order(
        struct xfs_buf  *node1_bp,
        struct xfs_buf  *node2_bp)
{
        xfs_da_intnode_t *node1, *node2;

        node1 = node1_bp->b_addr;
        node2 = node2_bp->b_addr;
        ASSERT(node1->hdr.info.magic == cpu_to_be16(XFS_DA_NODE_MAGIC) &&
               node2->hdr.info.magic == cpu_to_be16(XFS_DA_NODE_MAGIC));
        if ((be16_to_cpu(node1->hdr.count) > 0) && (be16_to_cpu(node2->hdr.count) > 0) &&
            ((be32_to_cpu(node2->btree[0].hashval) <
              be32_to_cpu(node1->btree[0].hashval)) ||
             (be32_to_cpu(node2->btree[be16_to_cpu(node2->hdr.count)-1].hashval) <
              be32_to_cpu(node1->btree[be16_to_cpu(node1->hdr.count)-1].hashval)))) {
                return(1);
        }
        return(0);
}

/*
 * Pick up the last hashvalue from an intermediate node.
 */
STATIC uint
xfs_da_node_lasthash(
        struct xfs_buf  *bp,
        int             *count)
{
        xfs_da_intnode_t *node;

        node = bp->b_addr;
        ASSERT(node->hdr.info.magic == cpu_to_be16(XFS_DA_NODE_MAGIC));
        if (count)
                *count = be16_to_cpu(node->hdr.count);
        if (!node->hdr.count)
                return(0);
        return be32_to_cpu(node->btree[be16_to_cpu(node->hdr.count)-1].hashval);
}

/*
 * Unlink a block from a doubly linked list of blocks.
 */
STATIC int                                              /* error */
xfs_da_blk_unlink(xfs_da_state_t *state, xfs_da_state_blk_t *drop_blk,
                                 xfs_da_state_blk_t *save_blk)
{
        xfs_da_blkinfo_t *drop_info, *save_info, *tmp_info;
        xfs_da_args_t *args;
        struct xfs_buf *bp;
        int error;

        /*
         * Set up environment.
         */
        args = state->args;
        ASSERT(args != NULL);
        save_info = save_blk->bp->b_addr;
        drop_info = drop_blk->bp->b_addr;
        ASSERT(save_blk->magic == XFS_DA_NODE_MAGIC ||
               save_blk->magic == XFS_DIR2_LEAFN_MAGIC ||
               save_blk->magic == XFS_ATTR_LEAF_MAGIC);
        ASSERT(save_blk->magic == be16_to_cpu(save_info->magic));
        ASSERT(drop_blk->magic == be16_to_cpu(drop_info->magic));
        ASSERT(save_blk->magic == drop_blk->magic);
        ASSERT((be32_to_cpu(save_info->forw) == drop_blk->blkno) ||
               (be32_to_cpu(save_info->back) == drop_blk->blkno));
        ASSERT((be32_to_cpu(drop_info->forw) == save_blk->blkno) ||
               (be32_to_cpu(drop_info->back) == save_blk->blkno));

        /*
         * Unlink the leaf block from the doubly linked chain of leaves.
         */
        if (be32_to_cpu(save_info->back) == drop_blk->blkno) {
                trace_xfs_da_unlink_back(args);
                save_info->back = drop_info->back;
                if (drop_info->back) {
                        error = xfs_da_read_buf(args->trans, args->dp,
                                                be32_to_cpu(drop_info->back),
                                                -1, &bp, args->whichfork);
                        if (error)
                                return(error);
                        ASSERT(bp != NULL);
                        tmp_info = bp->b_addr;
                        ASSERT(tmp_info->magic == save_info->magic);
                        ASSERT(be32_to_cpu(tmp_info->forw) == drop_blk->blkno);
                        tmp_info->forw = cpu_to_be32(save_blk->blkno);
                        xfs_trans_log_buf(args->trans, bp, 0,
                                                    sizeof(*tmp_info) - 1);
                }
        } else {
                trace_xfs_da_unlink_forward(args);
                save_info->forw = drop_info->forw;
                if (drop_info->forw) {
                        error = xfs_da_read_buf(args->trans, args->dp,
                                                be32_to_cpu(drop_info->forw),
                                                -1, &bp, args->whichfork);
                        if (error)
                                return(error);
                        ASSERT(bp != NULL);
                        tmp_info = bp->b_addr;
                        ASSERT(tmp_info->magic == save_info->magic);
                        ASSERT(be32_to_cpu(tmp_info->back) == drop_blk->blkno);
                        tmp_info->back = cpu_to_be32(save_blk->blkno);
                        xfs_trans_log_buf(args->trans, bp, 0,
                                                    sizeof(*tmp_info) - 1);
                }
        }

        xfs_trans_log_buf(args->trans, save_blk->bp, 0, sizeof(*save_info) - 1);
        return(0);
}

/*
 * Move a path "forward" or "!forward" one block at the current level.
 *
 * This routine will adjust a "path" to point to the next block
 * "forward" (higher hashvalues) or "!forward" (lower hashvals) in the
 * Btree, including updating pointers to the intermediate nodes between
 * the new bottom and the root.
 */
int                                                     /* error */
xfs_da_path_shift(xfs_da_state_t *state, xfs_da_state_path_t *path,
                                 int forward, int release, int *result)
{
        xfs_da_state_blk_t *blk;
        xfs_da_blkinfo_t *info;
        xfs_da_intnode_t *node;
        xfs_da_args_t *args;
        xfs_dablk_t blkno=0;
        int level, error;

        /*
         * Roll up the Btree looking for the first block where our
         * current index is not at the edge of the block.  Note that
         * we skip the bottom layer because we want the sibling block.
         */
        args = state->args;
        ASSERT(args != NULL);
        ASSERT(path != NULL);
        ASSERT((path->active > 0) && (path->active < XFS_DA_NODE_MAXDEPTH));
        level = (path->active-1) - 1;   /* skip bottom layer in path */
        for (blk = &path->blk[level]; level >= 0; blk--, level--) {
                ASSERT(blk->bp != NULL);
                node = blk->bp->b_addr;
                ASSERT(node->hdr.info.magic == cpu_to_be16(XFS_DA_NODE_MAGIC));
                if (forward && (blk->index < be16_to_cpu(node->hdr.count)-1)) {
                        blk->index++;
                        blkno = be32_to_cpu(node->btree[blk->index].before);
                        break;
                } else if (!forward && (blk->index > 0)) {
                        blk->index--;
                        blkno = be32_to_cpu(node->btree[blk->index].before);
                        break;
                }
        }
        if (level < 0) {
                *result = XFS_ERROR(ENOENT);    /* we're out of our tree */
                ASSERT(args->op_flags & XFS_DA_OP_OKNOENT);
                return(0);
        }

        /*
         * Roll down the edge of the subtree until we reach the
         * same depth we were at originally.
         */
        for (blk++, level++; level < path->active; blk++, level++) {
                /*
                 * Release the old block.
                 * (if it's dirty, trans won't actually let go)
                 */
                if (release)
                        xfs_trans_brelse(args->trans, blk->bp);

                /*
                 * Read the next child block.
                 */
                blk->blkno = blkno;
                error = xfs_da_read_buf(args->trans, args->dp, blkno, -1,
                                                     &blk->bp, args->whichfork);
                if (error)
                        return(error);
                ASSERT(blk->bp != NULL);
                info = blk->bp->b_addr;
                ASSERT(info->magic == cpu_to_be16(XFS_DA_NODE_MAGIC) ||
                       info->magic == cpu_to_be16(XFS_DIR2_LEAFN_MAGIC) ||
                       info->magic == cpu_to_be16(XFS_ATTR_LEAF_MAGIC));
                blk->magic = be16_to_cpu(info->magic);
                if (blk->magic == XFS_DA_NODE_MAGIC) {
                        node = (xfs_da_intnode_t *)info;
                        blk->hashval = be32_to_cpu(node->btree[be16_to_cpu(node->hdr.count)-1].hashval);
                        if (forward)
                                blk->index = 0;
                        else
                                blk->index = be16_to_cpu(node->hdr.count)-1;
                        blkno = be32_to_cpu(node->btree[blk->index].before);
                } else {
                        ASSERT(level == path->active-1);
                        blk->index = 0;
                        switch(blk->magic) {
                        case XFS_ATTR_LEAF_MAGIC:
                                blk->hashval = xfs_attr_leaf_lasthash(blk->bp,
                                                                      NULL);
                                break;
                        case XFS_DIR2_LEAFN_MAGIC:
                                blk->hashval = xfs_dir2_leafn_lasthash(blk->bp,
                                                                       NULL);
                                break;
                        default:
                                ASSERT(blk->magic == XFS_ATTR_LEAF_MAGIC ||
                                       blk->magic == XFS_DIR2_LEAFN_MAGIC);
                                break;
                        }
                }
        }
        *result = 0;
        return(0);
}


/*========================================================================
 * Utility routines.
 *========================================================================*/

/*
 * Implement a simple hash on a character string.
 * Rotate the hash value by 7 bits, then XOR each character in.
 * This is implemented with some source-level loop unrolling.
 */
xfs_dahash_t
xfs_da_hashname(const __uint8_t *name, int namelen)
{
        xfs_dahash_t hash;

        /*
         * Do four characters at a time as long as we can.
         */
        for (hash = 0; namelen >= 4; namelen -= 4, name += 4)
                hash = (name[0] << 21) ^ (name[1] << 14) ^ (name[2] << 7) ^
                       (name[3] << 0) ^ rol32(hash, 7 * 4);

        /*
         * Now do the rest of the characters.
         */
        switch (namelen) {
        case 3:
                return (name[0] << 14) ^ (name[1] << 7) ^ (name[2] << 0) ^
                       rol32(hash, 7 * 3);
        case 2:
                return (name[0] << 7) ^ (name[1] << 0) ^ rol32(hash, 7 * 2);
        case 1:
                return (name[0] << 0) ^ rol32(hash, 7 * 1);
        default: /* case 0: */
                return hash;
        }
}

enum xfs_dacmp
xfs_da_compname(
        struct xfs_da_args *args,
        const unsigned char *name,
        int             len)
{
        return (args->namelen == len && memcmp(args->name, name, len) == 0) ?
                                        XFS_CMP_EXACT : XFS_CMP_DIFFERENT;
}

static xfs_dahash_t
xfs_default_hashname(
        struct xfs_name *name)
{
        return xfs_da_hashname(name->name, name->len);
}

const struct xfs_nameops xfs_default_nameops = {
        .hashname       = xfs_default_hashname,
        .compname       = xfs_da_compname
};

int
xfs_da_grow_inode_int(
        struct xfs_da_args      *args,
        xfs_fileoff_t           *bno,
        int                     count)
{
        struct xfs_trans        *tp = args->trans;
        struct xfs_inode        *dp = args->dp;
        int                     w = args->whichfork;
        xfs_drfsbno_t           nblks = dp->i_d.di_nblocks;
        struct xfs_bmbt_irec    map, *mapp;
        int                     nmap, error, got, i, mapi;

        /*
         * Find a spot in the file space to put the new block.
         */
        error = xfs_bmap_first_unused(tp, dp, count, bno, w);
        if (error)
                return error;

        /*
         * Try mapping it in one filesystem block.
         */
        nmap = 1;
        ASSERT(args->firstblock != NULL);
        error = xfs_bmapi_write(tp, dp, *bno, count,
                        xfs_bmapi_aflag(w)|XFS_BMAPI_METADATA|XFS_BMAPI_CONTIG,
                        args->firstblock, args->total, &map, &nmap,
                        args->flist);
        if (error)
                return error;

        ASSERT(nmap <= 1);
        if (nmap == 1) {
                mapp = &map;
                mapi = 1;
        } else if (nmap == 0 && count > 1) {
                xfs_fileoff_t           b;
                int                     c;

                /*
                 * If we didn't get it and the block might work if fragmented,
                 * try without the CONTIG flag.  Loop until we get it all.
                 */
                mapp = kmem_alloc(sizeof(*mapp) * count, KM_SLEEP);
                for (b = *bno, mapi = 0; b < *bno + count; ) {
                        nmap = MIN(XFS_BMAP_MAX_NMAP, count);
                        c = (int)(*bno + count - b);
                        error = xfs_bmapi_write(tp, dp, b, c,
                                        xfs_bmapi_aflag(w)|XFS_BMAPI_METADATA,
                                        args->firstblock, args->total,
                                        &mapp[mapi], &nmap, args->flist);
                        if (error)
                                goto out_free_map;
                        if (nmap < 1)
                                break;
                        mapi += nmap;
                        b = mapp[mapi - 1].br_startoff +
                            mapp[mapi - 1].br_blockcount;
                }
        } else {
                mapi = 0;
                mapp = NULL;
        }

        /*
         * Count the blocks we got, make sure it matches the total.
         */
        for (i = 0, got = 0; i < mapi; i++)
                got += mapp[i].br_blockcount;
        if (got != count || mapp[0].br_startoff != *bno ||
            mapp[mapi - 1].br_startoff + mapp[mapi - 1].br_blockcount !=
            *bno + count) {
                error = XFS_ERROR(ENOSPC);
                goto out_free_map;
        }

        /* account for newly allocated blocks in reserved blocks total */
        args->total -= dp->i_d.di_nblocks - nblks;

out_free_map:
        if (mapp != &map)
                kmem_free(mapp);
        return error;
}

/*
 * Add a block to the btree ahead of the file.
 * Return the new block number to the caller.
 */
int
xfs_da_grow_inode(
        struct xfs_da_args      *args,
        xfs_dablk_t             *new_blkno)
{
        xfs_fileoff_t           bno;
        int                     count;
        int                     error;

        trace_xfs_da_grow_inode(args);

        if (args->whichfork == XFS_DATA_FORK) {
                bno = args->dp->i_mount->m_dirleafblk;
                count = args->dp->i_mount->m_dirblkfsbs;
        } else {
                bno = 0;
                count = 1;
        }

        error = xfs_da_grow_inode_int(args, &bno, count);
        if (!error)
                *new_blkno = (xfs_dablk_t)bno;
        return error;
}

/*
 * Ick.  We need to always be able to remove a btree block, even
 * if there's no space reservation because the filesystem is full.
 * This is called if xfs_bunmapi on a btree block fails due to ENOSPC.
 * It swaps the target block with the last block in the file.  The
 * last block in the file can always be removed since it can't cause
 * a bmap btree split to do that.
 */
STATIC int
xfs_da_swap_lastblock(
        xfs_da_args_t   *args,
        xfs_dablk_t     *dead_blknop,
        struct xfs_buf  **dead_bufp)
{
        xfs_dablk_t dead_blkno, last_blkno, sib_blkno, par_blkno;
        struct xfs_buf *dead_buf, *last_buf, *sib_buf, *par_buf;
        xfs_fileoff_t lastoff;
        xfs_inode_t *ip;
        xfs_trans_t *tp;
        xfs_mount_t *mp;
        int error, w, entno, level, dead_level;
        xfs_da_blkinfo_t *dead_info, *sib_info;
        xfs_da_intnode_t *par_node, *dead_node;
        xfs_dir2_leaf_t *dead_leaf2;
        xfs_dahash_t dead_hash;

        trace_xfs_da_swap_lastblock(args);

        dead_buf = *dead_bufp;
        dead_blkno = *dead_blknop;
        tp = args->trans;
        ip = args->dp;
        w = args->whichfork;
        ASSERT(w == XFS_DATA_FORK);
        mp = ip->i_mount;
        lastoff = mp->m_dirfreeblk;
        error = xfs_bmap_last_before(tp, ip, &lastoff, w);
        if (error)
                return error;
        if (unlikely(lastoff == 0)) {
                XFS_ERROR_REPORT("xfs_da_swap_lastblock(1)", XFS_ERRLEVEL_LOW,
                                 mp);
                return XFS_ERROR(EFSCORRUPTED);
        }
        /*
         * Read the last block in the btree space.
         */
        last_blkno = (xfs_dablk_t)lastoff - mp->m_dirblkfsbs;
        if ((error = xfs_da_read_buf(tp, ip, last_blkno, -1, &last_buf, w)))
                return error;
        /*
         * Copy the last block into the dead buffer and log it.
         */
        memcpy(dead_buf->b_addr, last_buf->b_addr, mp->m_dirblksize);
        xfs_trans_log_buf(tp, dead_buf, 0, mp->m_dirblksize - 1);
        dead_info = dead_buf->b_addr;
        /*
         * Get values from the moved block.
         */
        if (dead_info->magic == cpu_to_be16(XFS_DIR2_LEAFN_MAGIC)) {
                dead_leaf2 = (xfs_dir2_leaf_t *)dead_info;
                dead_level = 0;
                dead_hash = be32_to_cpu(dead_leaf2->ents[be16_to_cpu(dead_leaf2->hdr.count) - 1].hashval);
        } else {
                ASSERT(dead_info->magic == cpu_to_be16(XFS_DA_NODE_MAGIC));
                dead_node = (xfs_da_intnode_t *)dead_info;
                dead_level = be16_to_cpu(dead_node->hdr.level);
                dead_hash = be32_to_cpu(dead_node->btree[be16_to_cpu(dead_node->hdr.count) - 1].hashval);
        }
        sib_buf = par_buf = NULL;
        /*
         * If the moved block has a left sibling, fix up the pointers.
         */
        if ((sib_blkno = be32_to_cpu(dead_info->back))) {
                if ((error = xfs_da_read_buf(tp, ip, sib_blkno, -1, &sib_buf, w)))
                        goto done;
                sib_info = sib_buf->b_addr;
                if (unlikely(
                    be32_to_cpu(sib_info->forw) != last_blkno ||
                    sib_info->magic != dead_info->magic)) {
                        XFS_ERROR_REPORT("xfs_da_swap_lastblock(2)",
                                         XFS_ERRLEVEL_LOW, mp);
                        error = XFS_ERROR(EFSCORRUPTED);
                        goto done;
                }
                sib_info->forw = cpu_to_be32(dead_blkno);
                xfs_trans_log_buf(tp, sib_buf,
                        XFS_DA_LOGRANGE(sib_info, &sib_info->forw,
                                        sizeof(sib_info->forw)));
                sib_buf = NULL;
        }
        /*
         * If the moved block has a right sibling, fix up the pointers.
         */
        if ((sib_blkno = be32_to_cpu(dead_info->forw))) {
                if ((error = xfs_da_read_buf(tp, ip, sib_blkno, -1, &sib_buf, w)))
                        goto done;
                sib_info = sib_buf->b_addr;
                if (unlikely(
                       be32_to_cpu(sib_info->back) != last_blkno ||
                       sib_info->magic != dead_info->magic)) {
                        XFS_ERROR_REPORT("xfs_da_swap_lastblock(3)",
                                         XFS_ERRLEVEL_LOW, mp);
                        error = XFS_ERROR(EFSCORRUPTED);
                        goto done;
                }
                sib_info->back = cpu_to_be32(dead_blkno);
                xfs_trans_log_buf(tp, sib_buf,
                        XFS_DA_LOGRANGE(sib_info, &sib_info->back,
                                        sizeof(sib_info->back)));
                sib_buf = NULL;
        }
        par_blkno = mp->m_dirleafblk;
        level = -1;
        /*
         * Walk down the tree looking for the parent of the moved block.
         */
        for (;;) {
                if ((error = xfs_da_read_buf(tp, ip, par_blkno, -1, &par_buf, w)))
                        goto done;
                par_node = par_buf->b_addr;
                if (unlikely(par_node->hdr.info.magic !=
                    cpu_to_be16(XFS_DA_NODE_MAGIC) ||
                    (level >= 0 && level != be16_to_cpu(par_node->hdr.level) + 1))) {
                        XFS_ERROR_REPORT("xfs_da_swap_lastblock(4)",
                                         XFS_ERRLEVEL_LOW, mp);
                        error = XFS_ERROR(EFSCORRUPTED);
                        goto done;
                }
                level = be16_to_cpu(par_node->hdr.level);
                for (entno = 0;
                     entno < be16_to_cpu(par_node->hdr.count) &&
                     be32_to_cpu(par_node->btree[entno].hashval) < dead_hash;
                     entno++)
                        continue;
                if (unlikely(entno == be16_to_cpu(par_node->hdr.count))) {
                        XFS_ERROR_REPORT("xfs_da_swap_lastblock(5)",
                                         XFS_ERRLEVEL_LOW, mp);
                        error = XFS_ERROR(EFSCORRUPTED);
                        goto done;
                }
                par_blkno = be32_to_cpu(par_node->btree[entno].before);
                if (level == dead_level + 1)
                        break;
                xfs_trans_brelse(tp, par_buf);
                par_buf = NULL;
        }
        /*
         * We're in the right parent block.
         * Look for the right entry.
         */
        for (;;) {
                for (;
                     entno < be16_to_cpu(par_node->hdr.count) &&
                     be32_to_cpu(par_node->btree[entno].before) != last_blkno;
                     entno++)
                        continue;
                if (entno < be16_to_cpu(par_node->hdr.count))
                        break;
                par_blkno = be32_to_cpu(par_node->hdr.info.forw);
                xfs_trans_brelse(tp, par_buf);
                par_buf = NULL;
                if (unlikely(par_blkno == 0)) {
                        XFS_ERROR_REPORT("xfs_da_swap_lastblock(6)",
                                         XFS_ERRLEVEL_LOW, mp);
                        error = XFS_ERROR(EFSCORRUPTED);
                        goto done;
                }
                if ((error = xfs_da_read_buf(tp, ip, par_blkno, -1, &par_buf, w)))
                        goto done;
                par_node = par_buf->b_addr;
                if (unlikely(
                    be16_to_cpu(par_node->hdr.level) != level ||
                    par_node->hdr.info.magic != cpu_to_be16(XFS_DA_NODE_MAGIC))) {
                        XFS_ERROR_REPORT("xfs_da_swap_lastblock(7)",
                                         XFS_ERRLEVEL_LOW, mp);
                        error = XFS_ERROR(EFSCORRUPTED);
                        goto done;
                }
                entno = 0;
        }
        /*
         * Update the parent entry pointing to the moved block.
         */
        par_node->btree[entno].before = cpu_to_be32(dead_blkno);
        xfs_trans_log_buf(tp, par_buf,
                XFS_DA_LOGRANGE(par_node, &par_node->btree[entno].before,
                                sizeof(par_node->btree[entno].before)));
        *dead_blknop = last_blkno;
        *dead_bufp = last_buf;
        return 0;
done:
        if (par_buf)
                xfs_trans_brelse(tp, par_buf);
        if (sib_buf)
                xfs_trans_brelse(tp, sib_buf);
        xfs_trans_brelse(tp, last_buf);
        return error;
}

/*
 * Remove a btree block from a directory or attribute.
 */
int
xfs_da_shrink_inode(
        xfs_da_args_t   *args,
        xfs_dablk_t     dead_blkno,
        struct xfs_buf  *dead_buf)
{
        xfs_inode_t *dp;
        int done, error, w, count;
        xfs_trans_t *tp;
        xfs_mount_t *mp;

        trace_xfs_da_shrink_inode(args);

        dp = args->dp;
        w = args->whichfork;
        tp = args->trans;
        mp = dp->i_mount;
        if (w == XFS_DATA_FORK)
                count = mp->m_dirblkfsbs;
        else
                count = 1;
        for (;;) {
                /*
                 * Remove extents.  If we get ENOSPC for a dir we have to move
                 * the last block to the place we want to kill.
                 */
                if ((error = xfs_bunmapi(tp, dp, dead_blkno, count,
                                xfs_bmapi_aflag(w)|XFS_BMAPI_METADATA,
                                0, args->firstblock, args->flist,
                                &done)) == ENOSPC) {
                        if (w != XFS_DATA_FORK)
                                break;
                        if ((error = xfs_da_swap_lastblock(args, &dead_blkno,
                                        &dead_buf)))
                                break;
                } else {
                        break;
                }
        }
        xfs_trans_binval(tp, dead_buf);
        return error;
}

/*
 * See if the mapping(s) for this btree block are valid, i.e.
 * don't contain holes, are logically contiguous, and cover the whole range.
 */
STATIC int
xfs_da_map_covers_blocks(
        int             nmap,
        xfs_bmbt_irec_t *mapp,
        xfs_dablk_t     bno,
        int             count)
{
        int             i;
        xfs_fileoff_t   off;

        for (i = 0, off = bno; i < nmap; i++) {
                if (mapp[i].br_startblock == HOLESTARTBLOCK ||
                    mapp[i].br_startblock == DELAYSTARTBLOCK) {
                        return 0;
                }
                if (off != mapp[i].br_startoff) {
                        return 0;
                }
                off += mapp[i].br_blockcount;
        }
        return off == bno + count;
}

/*
 * Convert a struct xfs_bmbt_irec to a struct xfs_buf_map.
 *
 * For the single map case, it is assumed that the caller has provided a pointer
 * to a valid xfs_buf_map.  For the multiple map case, this function will
 * allocate the xfs_buf_map to hold all the maps and replace the caller's single
 * map pointer with the allocated map.
 */
static int
xfs_buf_map_from_irec(
        struct xfs_mount        *mp,
        struct xfs_buf_map      **mapp,
        unsigned int            *nmaps,
        struct xfs_bmbt_irec    *irecs,
        unsigned int            nirecs)
{
        struct xfs_buf_map      *map;
        int                     i;

        ASSERT(*nmaps == 1);
        ASSERT(nirecs >= 1);

        if (nirecs > 1) {
                map = kmem_zalloc(nirecs * sizeof(struct xfs_buf_map), KM_SLEEP);
                if (!map)
                        return ENOMEM;
                *mapp = map;
        }

        *nmaps = nirecs;
        map = *mapp;
        for (i = 0; i < *nmaps; i++) {
                ASSERT(irecs[i].br_startblock != DELAYSTARTBLOCK &&
                       irecs[i].br_startblock != HOLESTARTBLOCK);
                map[i].bm_bn = XFS_FSB_TO_DADDR(mp, irecs[i].br_startblock);
                map[i].bm_len = XFS_FSB_TO_BB(mp, irecs[i].br_blockcount);
        }
        return 0;
}

/*
 * Map the block we are given ready for reading. There are three possible return
 * values:
 *      -1 - will be returned if we land in a hole and mappedbno == -2 so the
 *           caller knows not to execute a subsequent read.
 *       0 - if we mapped the block successfully

 *      >0 - positive error number if there was an error.
 */
static int
xfs_dabuf_map(
        struct xfs_trans        *trans,
        struct xfs_inode        *dp,
        xfs_dablk_t             bno,
        xfs_daddr_t             mappedbno,
        int                     whichfork,
        struct xfs_buf_map      **map,
        int                     *nmaps)
{
        struct xfs_mount        *mp = dp->i_mount;
        int                     nfsb;
        int                     error = 0;
        struct xfs_bmbt_irec    irec;
        struct xfs_bmbt_irec    *irecs = &irec;
        int                     nirecs;

        ASSERT(map && *map);
        ASSERT(*nmaps == 1);

        nfsb = (whichfork == XFS_DATA_FORK) ? mp->m_dirblkfsbs : 1;

        /*
         * Caller doesn't have a mapping.  -2 means don't complain
         * if we land in a hole.
         */
        if (mappedbno == -1 || mappedbno == -2) {
                /*
                 * Optimize the one-block case.
                 */
                if (nfsb != 1)
                        irecs = kmem_zalloc(sizeof(irec) * nfsb, KM_SLEEP);

                nirecs = nfsb;
                error = xfs_bmapi_read(dp, (xfs_fileoff_t)bno, nfsb, irecs,
                                       &nirecs, xfs_bmapi_aflag(whichfork));
                if (error)
                        goto out;
        } else {
                irecs->br_startblock = XFS_DADDR_TO_FSB(mp, mappedbno);
                irecs->br_startoff = (xfs_fileoff_t)bno;
                irecs->br_blockcount = nfsb;
                irecs->br_state = 0;
                nirecs = 1;
        }

        if (!xfs_da_map_covers_blocks(nirecs, irecs, bno, nfsb)) {
                error = mappedbno == -2 ? -1 : XFS_ERROR(EFSCORRUPTED);
                if (unlikely(error == EFSCORRUPTED)) {
                        if (xfs_error_level >= XFS_ERRLEVEL_LOW) {
                                int i;
                                xfs_alert(mp, "%s: bno %lld dir: inode %lld",
                                        __func__, (long long)bno,
                                        (long long)dp->i_ino);
                                for (i = 0; i < *nmaps; i++) {
                                        xfs_alert(mp,
"[%02d] br_startoff %lld br_startblock %lld br_blockcount %lld br_state %d",
                                                i,
                                                (long long)irecs[i].br_startoff,
                                                (long long)irecs[i].br_startblock,
                                                (long long)irecs[i].br_blockcount,
                                                irecs[i].br_state);
                                }
                        }
                        XFS_ERROR_REPORT("xfs_da_do_buf(1)",
                                         XFS_ERRLEVEL_LOW, mp);
                }
                goto out;
        }
        error = xfs_buf_map_from_irec(mp, map, nmaps, irecs, nirecs);
out:
        if (irecs != &irec)
                kmem_free(irecs);
        return error;
}

/*
 * Get a buffer for the dir/attr block.
 */
int
xfs_da_get_buf(
        struct xfs_trans        *trans,
        struct xfs_inode        *dp,
        xfs_dablk_t             bno,
        xfs_daddr_t             mappedbno,
        struct xfs_buf          **bpp,
        int                     whichfork)
{
        struct xfs_buf          *bp;
        struct xfs_buf_map      map;
        struct xfs_buf_map      *mapp;
        int                     nmap;
        int                     error;

        *bpp = NULL;
        mapp = &map;
        nmap = 1;
        error = xfs_dabuf_map(trans, dp, bno, mappedbno, whichfork,
                                &mapp, &nmap);
        if (error) {
                /* mapping a hole is not an error, but we don't continue */
                if (error == -1)
                        error = 0;
                goto out_free;
        }

        bp = xfs_trans_get_buf_map(trans, dp->i_mount->m_ddev_targp,
                                    mapp, nmap, 0);
        error = bp ? bp->b_error : XFS_ERROR(EIO);
        if (error) {
                xfs_trans_brelse(trans, bp);
                goto out_free;
        }

        *bpp = bp;

out_free:
        if (mapp != &map)
                kmem_free(mapp);

        return error;
}

/*
 * Get a buffer for the dir/attr block, fill in the contents.
 */
int
xfs_da_read_buf(
        struct xfs_trans        *trans,
        struct xfs_inode        *dp,
        xfs_dablk_t             bno,
        xfs_daddr_t             mappedbno,
        struct xfs_buf          **bpp,
        int                     whichfork)
{
        struct xfs_buf          *bp;
        struct xfs_buf_map      map;
        struct xfs_buf_map      *mapp;
        int                     nmap;
        int                     error;

        *bpp = NULL;
        mapp = &map;
        nmap = 1;
        error = xfs_dabuf_map(trans, dp, bno, mappedbno, whichfork,
                                &mapp, &nmap);
        if (error) {
                /* mapping a hole is not an error, but we don't continue */
                if (error == -1)
                        error = 0;
                goto out_free;
        }

        error = xfs_trans_read_buf_map(dp->i_mount, trans,
                                        dp->i_mount->m_ddev_targp,
                                        mapp, nmap, 0, &bp);
        if (error)
                goto out_free;

        if (whichfork == XFS_ATTR_FORK)
                xfs_buf_set_ref(bp, XFS_ATTR_BTREE_REF);
        else
                xfs_buf_set_ref(bp, XFS_DIR_BTREE_REF);

        /*
         * This verification code will be moved to a CRC verification callback
         * function so just leave it here unchanged until then.
         */
        {
                xfs_dir2_data_hdr_t     *hdr = bp->b_addr;
                xfs_dir2_free_t         *free = bp->b_addr;
                xfs_da_blkinfo_t        *info = bp->b_addr;
                uint                    magic, magic1;
                struct xfs_mount        *mp = dp->i_mount;

                magic = be16_to_cpu(info->magic);
                magic1 = be32_to_cpu(hdr->magic);
                if (unlikely(
                    XFS_TEST_ERROR((magic != XFS_DA_NODE_MAGIC) &&
                                   (magic != XFS_ATTR_LEAF_MAGIC) &&
                                   (magic != XFS_DIR2_LEAF1_MAGIC) &&
                                   (magic != XFS_DIR2_LEAFN_MAGIC) &&
                                   (magic1 != XFS_DIR2_BLOCK_MAGIC) &&
                                   (magic1 != XFS_DIR2_DATA_MAGIC) &&
                                   (free->hdr.magic != cpu_to_be32(XFS_DIR2_FREE_MAGIC)),
                                mp, XFS_ERRTAG_DA_READ_BUF,
                                XFS_RANDOM_DA_READ_BUF))) {
                        trace_xfs_da_btree_corrupt(bp, _RET_IP_);
                        XFS_CORRUPTION_ERROR("xfs_da_do_buf(2)",
                                             XFS_ERRLEVEL_LOW, mp, info);
                        error = XFS_ERROR(EFSCORRUPTED);
                        xfs_trans_brelse(trans, bp);
                        goto out_free;
                }
        }
        *bpp = bp;
out_free:
        if (mapp != &map)
                kmem_free(mapp);

        return error;
}

/*
 * Readahead the dir/attr block.
 */
xfs_daddr_t
xfs_da_reada_buf(
        struct xfs_trans        *trans,
        struct xfs_inode        *dp,
        xfs_dablk_t             bno,
        int                     whichfork)
{
        xfs_daddr_t             mappedbno = -1;
        struct xfs_buf_map      map;
        struct xfs_buf_map      *mapp;
        int                     nmap;
        int                     error;

        mapp = &map;
        nmap = 1;
        error = xfs_dabuf_map(trans, dp, bno, -1, whichfork,
                                &mapp, &nmap);
        if (error) {
                /* mapping a hole is not an error, but we don't continue */
                if (error == -1)
                        error = 0;
                goto out_free;
        }

        mappedbno = mapp[0].bm_bn;
        xfs_buf_readahead_map(dp->i_mount->m_ddev_targp, mapp, nmap);

out_free:
        if (mapp != &map)
                kmem_free(mapp);

        if (error)
                return -1;
        return mappedbno;
}

kmem_zone_t *xfs_da_state_zone; /* anchor for state struct zone */

/*
 * Allocate a dir-state structure.
 * We don't put them on the stack since they're large.
 */
xfs_da_state_t *
xfs_da_state_alloc(void)
{
        return kmem_zone_zalloc(xfs_da_state_zone, KM_NOFS);
}

/*
 * Kill the altpath contents of a da-state structure.
 */
STATIC void
xfs_da_state_kill_altpath(xfs_da_state_t *state)
{
        int     i;

        for (i = 0; i < state->altpath.active; i++)
                state->altpath.blk[i].bp = NULL;
        state->altpath.active = 0;
}

/*
 * Free a da-state structure.
 */
void
xfs_da_state_free(xfs_da_state_t *state)
{
        xfs_da_state_kill_altpath(state);
#ifdef DEBUG
        memset((char *)state, 0, sizeof(*state));
#endif /* DEBUG */
        kmem_zone_free(xfs_da_state_zone, state);
}