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xfs_da_btree.c

/*
 * 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_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_da_btree.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_inode_item.h"
#include "xfs_alloc.h"
#include "xfs_btree.h"
#include "xfs_bmap.h"
#include "xfs_attr.h"
#include "xfs_attr_leaf.h"
#include "xfs_dir2_data.h"
#include "xfs_dir2_leaf.h"
#include "xfs_dir2_block.h"
#include "xfs_dir2_node.h"
#include "xfs_error.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(xfs_dabuf_t *bp, int *count);
STATIC int  xfs_da_node_order(xfs_dabuf_t *node1_bp, xfs_dabuf_t *node2_bp);
STATIC xfs_dabuf_t *xfs_da_buf_make(int nbuf, xfs_buf_t **bps, inst_t *ra);
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,
                         xfs_dabuf_t **bpp, int whichfork)
{
      xfs_da_intnode_t *node;
      xfs_dabuf_t *bp;
      int error;
      xfs_trans_t *tp;

      tp = args->trans;
      error = xfs_da_get_buf(tp, args->dp, blkno, -1, &bp, whichfork);
      if (error)
            return(error);
      ASSERT(bp != NULL);
      node = bp->data;
      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_da_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;
      xfs_dabuf_t *bp;
      int max, action, error, i;

      /*
       * 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 */
                        error = xfs_attr_leaf_split(state, oldblk,
                                              &state->extrablk);
                  } else {
                        state->extraafter = 1;  /* after newblk */
                        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);
                  xfs_da_buf_done(addblk->bp);
                  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 we won't need this block again, it's getting dropped
             * from the active path by the loop control, so we need
             * to mark it done now.
             */
            if (i > 0 || !addblk)
                  xfs_da_buf_done(oldblk->bp);
      }
      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) {
            xfs_da_buf_done(oldblk->bp);
            xfs_da_buf_done(addblk->bp);
            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->data;
      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->data;
            node->hdr.info.back = cpu_to_be32(oldblk->blkno);
            xfs_da_log_buf(state->args->trans, bp,
                XFS_DA_LOGRANGE(node, &node->hdr.info,
                sizeof(node->hdr.info)));
      }
      node = oldblk->bp->data;
      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->data;
            node->hdr.info.forw = cpu_to_be32(oldblk->blkno);
            xfs_da_log_buf(state->args->trans, bp,
                XFS_DA_LOGRANGE(node, &node->hdr.info,
                sizeof(node->hdr.info)));
      }
      xfs_da_buf_done(oldblk->bp);
      xfs_da_buf_done(addblk->bp);
      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;
      xfs_dabuf_t *bp;
      int error, size;
      xfs_inode_t *dp;
      xfs_trans_t *tp;
      xfs_mount_t *mp;
      xfs_dir2_leaf_t *leaf;

      /*
       * 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->data;
      oldroot = blk1->bp->data;
      if (be16_to_cpu(oldroot->hdr.info.magic) == XFS_DA_NODE_MAGIC) {
            size = (int)((char *)&oldroot->btree[be16_to_cpu(oldroot->hdr.count)] -
                       (char *)oldroot);
      } else {
            ASSERT(be16_to_cpu(oldroot->hdr.info.magic) == 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_da_log_buf(tp, bp, 0, size - 1);
      xfs_da_buf_done(blk1->bp);
      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->data;
      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 (be16_to_cpu(oldroot->hdr.info.magic) == 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_da_log_buf(tp, bp,
            XFS_DA_LOGRANGE(node, node->btree,
                  sizeof(xfs_da_node_entry_t) * 2));
      xfs_da_buf_done(bp);

      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;

      node = oldblk->bp->data;
      ASSERT(be16_to_cpu(node->hdr.info.magic) == 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->data;
      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;

      node1 = blk1->bp->data;
      node2 = blk2->bp->data;
      /*
       * 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(be16_to_cpu(node1->hdr.info.magic) == XFS_DA_NODE_MAGIC);
      ASSERT(be16_to_cpu(node2->hdr.info.magic) == 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(&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(&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(&node1->hdr.count, count);
            xfs_da_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(&node2->hdr.count, -count);
      }

      /*
       * Log header of node 1 and all current bits of node 2.
       */
      xfs_da_log_buf(tp, blk1->bp,
            XFS_DA_LOGRANGE(node1, &node1->hdr, sizeof(node1->hdr)));
      xfs_da_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->data;
      node2 = blk2->bp->data;
      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;
      xfs_mount_t *mp;

      node = oldblk->bp->data;
      mp = state->mp;
      ASSERT(be16_to_cpu(node->hdr.info.magic) == 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 >= mp->m_dirleafblk &&
                   newblk->blkno < 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_da_log_buf(state->args->trans, oldblk->bp,
            XFS_DA_LOGRANGE(node, btree, tmp + sizeof(*btree)));
      be16_add(&node->hdr.count, 1);
      xfs_da_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;

      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);
}

/*
 * 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;
      /* REFERENCED */
      xfs_da_blkinfo_t *blkinfo;
      xfs_da_args_t *args;
      xfs_dablk_t child;
      xfs_dabuf_t *bp;
      int error;

      args = state->args;
      ASSERT(args != NULL);
      ASSERT(root_blk->magic == XFS_DA_NODE_MAGIC);
      oldroot = root_blk->bp->data;
      ASSERT(be16_to_cpu(oldroot->hdr.info.magic) == 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);
      blkinfo = bp->data;
      if (be16_to_cpu(oldroot->hdr.level) == 1) {
            ASSERT(be16_to_cpu(blkinfo->magic) == XFS_DIR2_LEAFN_MAGIC ||
                   be16_to_cpu(blkinfo->magic) == XFS_ATTR_LEAF_MAGIC);
      } else {
            ASSERT(be16_to_cpu(blkinfo->magic) == XFS_DA_NODE_MAGIC);
      }
      ASSERT(!blkinfo->forw);
      ASSERT(!blkinfo->back);
      memcpy(root_blk->bp->data, bp->data, state->blocksize);
      xfs_da_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;
      xfs_dabuf_t *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->data;
      ASSERT(be16_to_cpu(info->magic) == 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->data;
            ASSERT(be16_to_cpu(node->hdr.info.magic) == XFS_DA_NODE_MAGIC);
            count -= be16_to_cpu(node->hdr.count);
            xfs_da_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->data;
            ASSERT(be16_to_cpu(node->hdr.info.magic) == 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_da_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;

      node = drop_blk->bp->data;
      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_da_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_da_log_buf(state->args->trans, drop_blk->bp,
          XFS_DA_LOGRANGE(node, btree, sizeof(*btree)));
      be16_add(&node->hdr.count, -1);
      xfs_da_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;

      drop_node = drop_blk->bp->data;
      save_node = save_blk->bp->data;
      ASSERT(be16_to_cpu(drop_node->hdr.info.magic) == XFS_DA_NODE_MAGIC);
      ASSERT(be16_to_cpu(save_node->hdr.info.magic) == 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_da_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_da_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(&save_node->hdr.count, be16_to_cpu(drop_node->hdr.count));

      xfs_da_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;
      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->data;
            ASSERT(be16_to_cpu(curr->magic) == XFS_DA_NODE_MAGIC ||
                   be16_to_cpu(curr->magic) == XFS_DIR2_LEAFN_MAGIC ||
                   be16_to_cpu(curr->magic) == XFS_ATTR_LEAF_MAGIC);

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

                  /*
                   * Binary search.  (note: small blocks will skip loop)
                   */
                  max = be16_to_cpu(node->hdr.count);
                  probe = span = max / 2;
                  hashval = args->hashval;
                  for (btree = &node->btree[probe]; span > 4;
                           btree = &node->btree[probe]) {
                        span /= 2;
                        if (be32_to_cpu(btree->hashval) < hashval)
                              probe += span;
                        else if (be32_to_cpu(btree->hashval) > 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 (be16_to_cpu(curr->magic) == XFS_ATTR_LEAF_MAGIC) {
                  blk->hashval = xfs_attr_leaf_lasthash(blk->bp, NULL);
                  break;
            } else if (be16_to_cpu(curr->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;
            }
            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;
      xfs_dabuf_t *bp;

      /*
       * Set up environment.
       */
      args = state->args;
      ASSERT(args != NULL);
      old_info = old_blk->bp->data;
      new_info = new_blk->bp->data;
      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.
             */
            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->data;
                  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_da_log_buf(args->trans, bp, 0, sizeof(*tmp_info)-1);
                  xfs_da_buf_done(bp);
            }
            old_info->back = cpu_to_be32(new_blk->blkno);
      } else {
            /*
             * Link new block in after existing block.
             */
            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->data;
                  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_da_log_buf(args->trans, bp, 0, sizeof(*tmp_info)-1);
                  xfs_da_buf_done(bp);
            }
            old_info->forw = cpu_to_be32(new_blk->blkno);
      }

      xfs_da_log_buf(args->trans, old_blk->bp, 0, sizeof(*tmp_info) - 1);
      xfs_da_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(xfs_dabuf_t *node1_bp, xfs_dabuf_t *node2_bp)
{
      xfs_da_intnode_t *node1, *node2;

      node1 = node1_bp->data;
      node2 = node2_bp->data;
      ASSERT((be16_to_cpu(node1->hdr.info.magic) == XFS_DA_NODE_MAGIC) &&
             (be16_to_cpu(node2->hdr.info.magic) == 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(xfs_dabuf_t *bp, int *count)
{
      xfs_da_intnode_t *node;

      node = bp->data;
      ASSERT(be16_to_cpu(node->hdr.info.magic) == 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;
      xfs_dabuf_t *bp;
      int error;

      /*
       * Set up environment.
       */
      args = state->args;
      ASSERT(args != NULL);
      save_info = save_blk->bp->data;
      drop_info = drop_blk->bp->data;
      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) {
            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->data;
                  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_da_log_buf(args->trans, bp, 0,
                                        sizeof(*tmp_info) - 1);
                  xfs_da_buf_done(bp);
            }
      } else {
            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->data;
                  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_da_log_buf(args->trans, bp, 0,
                                        sizeof(*tmp_info) - 1);
                  xfs_da_buf_done(bp);
            }
      }

      xfs_da_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->data;
            ASSERT(be16_to_cpu(node->hdr.info.magic) == 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->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_da_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->data;
            ASSERT(be16_to_cpu(info->magic) == XFS_DA_NODE_MAGIC ||
                   be16_to_cpu(info->magic) == XFS_DIR2_LEAFN_MAGIC ||
                   be16_to_cpu(info->magic) == 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 uchar_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;
      }
}

/*
 * Add a block to the btree ahead of the file.
 * Return the new block number to the caller.
 */
int
xfs_da_grow_inode(xfs_da_args_t *args, xfs_dablk_t *new_blkno)
{
      xfs_fileoff_t bno, b;
      xfs_bmbt_irec_t map;
      xfs_bmbt_irec_t   *mapp;
      xfs_inode_t *dp;
      int nmap, error, w, count, c, got, i, mapi;
      xfs_trans_t *tp;
      xfs_mount_t *mp;

      dp = args->dp;
      mp = dp->i_mount;
      w = args->whichfork;
      tp = args->trans;
      /*
       * For new directories adjust the file offset and block count.
       */
      if (w == XFS_DATA_FORK) {
            bno = mp->m_dirleafblk;
            count = mp->m_dirblkfsbs;
      } else {
            bno = 0;
            count = 1;
      }
      /*
       * Find a spot in the file space to put the new block.
       */
      if ((error = xfs_bmap_first_unused(tp, dp, count, &bno, w)))
            return error;
      if (w == XFS_DATA_FORK)
            ASSERT(bno >= mp->m_dirleafblk && bno < mp->m_dirfreeblk);
      /*
       * Try mapping it in one filesystem block.
       */
      nmap = 1;
      ASSERT(args->firstblock != NULL);
      if ((error = xfs_bmapi(tp, dp, bno, count,
                  XFS_BMAPI_AFLAG(w)|XFS_BMAPI_WRITE|XFS_BMAPI_METADATA|
                  XFS_BMAPI_CONTIG,
                  args->firstblock, args->total, &map, &nmap,
                  args->flist, NULL))) {
            return error;
      }
      ASSERT(nmap <= 1);
      if (nmap == 1) {
            mapp = &map;
            mapi = 1;
      }
      /*
       * If we didn't get it and the block might work if fragmented,
       * try without the CONTIG flag.  Loop until we get it all.
       */
      else if (nmap == 0 && count > 1) {
            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);
                  if ((error = xfs_bmapi(tp, dp, b, c,
                              XFS_BMAPI_AFLAG(w)|XFS_BMAPI_WRITE|
                              XFS_BMAPI_METADATA,
                              args->firstblock, args->total,
                              &mapp[mapi], &nmap, args->flist,
                              NULL))) {
                        kmem_free(mapp, sizeof(*mapp) * count);
                        return error;
                  }
                  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) {
            if (mapp != &map)
                  kmem_free(mapp, sizeof(*mapp) * count);
            return XFS_ERROR(ENOSPC);
      }
      if (mapp != &map)
            kmem_free(mapp, sizeof(*mapp) * count);
      *new_blkno = (xfs_dablk_t)bno;
      return 0;
}

/*
 * 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,
                  xfs_dabuf_t **dead_bufp)
{
      xfs_dablk_t dead_blkno, last_blkno, sib_blkno, par_blkno;
      xfs_dabuf_t *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;

      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->data, last_buf->data, mp->m_dirblksize);
      xfs_da_log_buf(tp, dead_buf, 0, mp->m_dirblksize - 1);
      dead_info = dead_buf->data;
      /*
       * Get values from the moved block.
       */
      if (be16_to_cpu(dead_info->magic) == 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(be16_to_cpu(dead_info->magic) == 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->data;
            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_da_log_buf(tp, sib_buf,
                  XFS_DA_LOGRANGE(sib_info, &sib_info->forw,
                              sizeof(sib_info->forw)));
            xfs_da_buf_done(sib_buf);
            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->data;
            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_da_log_buf(tp, sib_buf,
                  XFS_DA_LOGRANGE(sib_info, &sib_info->back,
                              sizeof(sib_info->back)));
            xfs_da_buf_done(sib_buf);
            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->data;
            if (unlikely(
                be16_to_cpu(par_node->hdr.info.magic) != 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_da_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_da_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->data;
            if (unlikely(
                be16_to_cpu(par_node->hdr.level) != level ||
                be16_to_cpu(par_node->hdr.info.magic) != 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_da_log_buf(tp, par_buf,
            XFS_DA_LOGRANGE(par_node, &par_node->btree[entno].before,
                        sizeof(par_node->btree[entno].before)));
      xfs_da_buf_done(par_buf);
      xfs_da_buf_done(dead_buf);
      *dead_blknop = last_blkno;
      *dead_bufp = last_buf;
      return 0;
done:
      if (par_buf)
            xfs_da_brelse(tp, par_buf);
      if (sib_buf)
            xfs_da_brelse(tp, sib_buf);
      xfs_da_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,
                xfs_dabuf_t *dead_buf)
{
      xfs_inode_t *dp;
      int done, error, w, count;
      xfs_trans_t *tp;
      xfs_mount_t *mp;

      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, NULL,
                        &done)) == ENOSPC) {
                  if (w != XFS_DATA_FORK)
                        break;
                  if ((error = xfs_da_swap_lastblock(args, &dead_blkno,
                              &dead_buf)))
                        break;
            } else {
                  break;
            }
      }
      xfs_da_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;
}

/*
 * Make a dabuf.
 * Used for get_buf, read_buf, read_bufr, and reada_buf.
 */
STATIC int
xfs_da_do_buf(
      xfs_trans_t *trans,
      xfs_inode_t *dp,
      xfs_dablk_t bno,
      xfs_daddr_t *mappedbnop,
      xfs_dabuf_t **bpp,
      int         whichfork,
      int         caller,
      inst_t            *ra)
{
      xfs_buf_t   *bp = NULL;
      xfs_buf_t   **bplist;
      int         error=0;
      int         i;
      xfs_bmbt_irec_t   map;
      xfs_bmbt_irec_t   *mapp;
      xfs_daddr_t mappedbno;
      xfs_mount_t *mp;
      int         nbplist=0;
      int         nfsb;
      int         nmap;
      xfs_dabuf_t *rbp;

      mp = dp->i_mount;
      nfsb = (whichfork == XFS_DATA_FORK) ? mp->m_dirblkfsbs : 1;
      mappedbno = *mappedbnop;
      /*
       * 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) {
                  xfs_fsblock_t     fsb;

                  if ((error =
                      xfs_bmapi_single(trans, dp, whichfork, &fsb,
                            (xfs_fileoff_t)bno))) {
                        return error;
                  }
                  mapp = &map;
                  if (fsb == NULLFSBLOCK) {
                        nmap = 0;
                  } else {
                        map.br_startblock = fsb;
                        map.br_startoff = (xfs_fileoff_t)bno;
                        map.br_blockcount = 1;
                        nmap = 1;
                  }
            } else {
                  mapp = kmem_alloc(sizeof(*mapp) * nfsb, KM_SLEEP);
                  nmap = nfsb;
                  if ((error = xfs_bmapi(trans, dp, (xfs_fileoff_t)bno,
                              nfsb,
                              XFS_BMAPI_METADATA |
                                    XFS_BMAPI_AFLAG(whichfork),
                              NULL, 0, mapp, &nmap, NULL, NULL)))
                        goto exit0;
            }
      } else {
            map.br_startblock = XFS_DADDR_TO_FSB(mp, mappedbno);
            map.br_startoff = (xfs_fileoff_t)bno;
            map.br_blockcount = nfsb;
            mapp = &map;
            nmap = 1;
      }
      if (!xfs_da_map_covers_blocks(nmap, mapp, bno, nfsb)) {
            error = mappedbno == -2 ? 0 : XFS_ERROR(EFSCORRUPTED);
            if (unlikely(error == EFSCORRUPTED)) {
                  if (xfs_error_level >= XFS_ERRLEVEL_LOW) {
                        int   i;
                        cmn_err(CE_ALERT, "xfs_da_do_buf: bno %lld\n",
                              (long long)bno);
                        cmn_err(CE_ALERT, "dir: inode %lld\n",
                              (long long)dp->i_ino);
                        for (i = 0; i < nmap; i++) {
                              cmn_err(CE_ALERT,
                                    "[%02d] br_startoff %lld br_startblock %lld br_blockcount %lld br_state %d\n",
                                    i,
                                    (long long)mapp[i].br_startoff,
                                    (long long)mapp[i].br_startblock,
                                    (long long)mapp[i].br_blockcount,
                                    mapp[i].br_state);
                        }
                  }
                  XFS_ERROR_REPORT("xfs_da_do_buf(1)",
                               XFS_ERRLEVEL_LOW, mp);
            }
            goto exit0;
      }
      if (caller != 3 && nmap > 1) {
            bplist = kmem_alloc(sizeof(*bplist) * nmap, KM_SLEEP);
            nbplist = 0;
      } else
            bplist = NULL;
      /*
       * Turn the mapping(s) into buffer(s).
       */
      for (i = 0; i < nmap; i++) {
            int   nmapped;

            mappedbno = XFS_FSB_TO_DADDR(mp, mapp[i].br_startblock);
            if (i == 0)
                  *mappedbnop = mappedbno;
            nmapped = (int)XFS_FSB_TO_BB(mp, mapp[i].br_blockcount);
            switch (caller) {
            case 0:
                  bp = xfs_trans_get_buf(trans, mp->m_ddev_targp,
                        mappedbno, nmapped, 0);
                  error = bp ? XFS_BUF_GETERROR(bp) : XFS_ERROR(EIO);
                  break;
            case 1:
            case 2:
                  bp = NULL;
                  error = xfs_trans_read_buf(mp, trans, mp->m_ddev_targp,
                        mappedbno, nmapped, 0, &bp);
                  break;
            case 3:
                  xfs_baread(mp->m_ddev_targp, mappedbno, nmapped);
                  error = 0;
                  bp = NULL;
                  break;
            }
            if (error) {
                  if (bp)
                        xfs_trans_brelse(trans, bp);
                  goto exit1;
            }
            if (!bp)
                  continue;
            if (caller == 1) {
                  if (whichfork == XFS_ATTR_FORK) {
                        XFS_BUF_SET_VTYPE_REF(bp, B_FS_ATTR_BTREE,
                                    XFS_ATTR_BTREE_REF);
                  } else {
                        XFS_BUF_SET_VTYPE_REF(bp, B_FS_DIR_BTREE,
                                    XFS_DIR_BTREE_REF);
                  }
            }
            if (bplist) {
                  bplist[nbplist++] = bp;
            }
      }
      /*
       * Build a dabuf structure.
       */
      if (bplist) {
            rbp = xfs_da_buf_make(nbplist, bplist, ra);
      } else if (bp)
            rbp = xfs_da_buf_make(1, &bp, ra);
      else
            rbp = NULL;
      /*
       * For read_buf, check the magic number.
       */
      if (caller == 1) {
            xfs_dir2_data_t         *data;
            xfs_dir2_free_t         *free;
            xfs_da_blkinfo_t  *info;
            uint              magic, magic1;

            info = rbp->data;
            data = rbp->data;
            free = rbp->data;
            magic = be16_to_cpu(info->magic);
            magic1 = be32_to_cpu(data->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) &&
                           (be32_to_cpu(free->hdr.magic) != XFS_DIR2_FREE_MAGIC),
                        mp, XFS_ERRTAG_DA_READ_BUF,
                        XFS_RANDOM_DA_READ_BUF))) {
                  xfs_buftrace("DA READ ERROR", rbp->bps[0]);
                  XFS_CORRUPTION_ERROR("xfs_da_do_buf(2)",
                                   XFS_ERRLEVEL_LOW, mp, info);
                  error = XFS_ERROR(EFSCORRUPTED);
                  xfs_da_brelse(trans, rbp);
                  nbplist = 0;
                  goto exit1;
            }
      }
      if (bplist) {
            kmem_free(bplist, sizeof(*bplist) * nmap);
      }
      if (mapp != &map) {
            kmem_free(mapp, sizeof(*mapp) * nfsb);
      }
      if (bpp)
            *bpp = rbp;
      return 0;
exit1:
      if (bplist) {
            for (i = 0; i < nbplist; i++)
                  xfs_trans_brelse(trans, bplist[i]);
            kmem_free(bplist, sizeof(*bplist) * nmap);
      }
exit0:
      if (mapp != &map)
            kmem_free(mapp, sizeof(*mapp) * nfsb);
      if (bpp)
            *bpp = NULL;
      return error;
}

/*
 * Get a buffer for the dir/attr block.
 */
int
xfs_da_get_buf(
      xfs_trans_t *trans,
      xfs_inode_t *dp,
      xfs_dablk_t bno,
      xfs_daddr_t       mappedbno,
      xfs_dabuf_t **bpp,
      int         whichfork)
{
      return xfs_da_do_buf(trans, dp, bno, &mappedbno, bpp, whichfork, 0,
                                     (inst_t *)__return_address);
}

/*
 * Get a buffer for the dir/attr block, fill in the contents.
 */
int
xfs_da_read_buf(
      xfs_trans_t *trans,
      xfs_inode_t *dp,
      xfs_dablk_t bno,
      xfs_daddr_t       mappedbno,
      xfs_dabuf_t **bpp,
      int         whichfork)
{
      return xfs_da_do_buf(trans, dp, bno, &mappedbno, bpp, whichfork, 1,
            (inst_t *)__return_address);
}

/*
 * Readahead the dir/attr block.
 */
xfs_daddr_t
xfs_da_reada_buf(
      xfs_trans_t *trans,
      xfs_inode_t *dp,
      xfs_dablk_t bno,
      int         whichfork)
{
      xfs_daddr_t       rval;

      rval = -1;
      if (xfs_da_do_buf(trans, dp, bno, &rval, NULL, whichfork, 3,
                  (inst_t *)__return_address))
            return -1;
      else
            return rval;
}

/*
 * Calculate the number of bits needed to hold i different values.
 */
uint
xfs_da_log2_roundup(uint i)
{
      uint rval;

      for (rval = 0; rval < NBBY * sizeof(i); rval++) {
            if ((1 << rval) >= i)
                  break;
      }
      return(rval);
}

kmem_zone_t *xfs_da_state_zone;     /* anchor for state struct zone */
kmem_zone_t *xfs_dabuf_zone;        /* dabuf 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_SLEEP);
}

/*
 * 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++) {
            if (state->altpath.blk[i].bp) {
                  if (state->altpath.blk[i].bp != state->path.blk[i].bp)
                        xfs_da_buf_done(state->altpath.blk[i].bp);
                  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)
{
      int   i;

      xfs_da_state_kill_altpath(state);
      for (i = 0; i < state->path.active; i++) {
            if (state->path.blk[i].bp)
                  xfs_da_buf_done(state->path.blk[i].bp);
      }
      if (state->extravalid && state->extrablk.bp)
            xfs_da_buf_done(state->extrablk.bp);
#ifdef DEBUG
      memset((char *)state, 0, sizeof(*state));
#endif /* DEBUG */
      kmem_zone_free(xfs_da_state_zone, state);
}

#ifdef XFS_DABUF_DEBUG
xfs_dabuf_t *xfs_dabuf_global_list;
lock_t            xfs_dabuf_global_lock;
#endif

/*
 * Create a dabuf.
 */
/* ARGSUSED */
STATIC xfs_dabuf_t *
xfs_da_buf_make(int nbuf, xfs_buf_t **bps, inst_t *ra)
{
      xfs_buf_t   *bp;
      xfs_dabuf_t *dabuf;
      int         i;
      int         off;

      if (nbuf == 1)
            dabuf = kmem_zone_alloc(xfs_dabuf_zone, KM_SLEEP);
      else
            dabuf = kmem_alloc(XFS_DA_BUF_SIZE(nbuf), KM_SLEEP);
      dabuf->dirty = 0;
#ifdef XFS_DABUF_DEBUG
      dabuf->ra = ra;
      dabuf->target = XFS_BUF_TARGET(bps[0]);
      dabuf->blkno = XFS_BUF_ADDR(bps[0]);
#endif
      if (nbuf == 1) {
            dabuf->nbuf = 1;
            bp = bps[0];
            dabuf->bbcount = (short)BTOBB(XFS_BUF_COUNT(bp));
            dabuf->data = XFS_BUF_PTR(bp);
            dabuf->bps[0] = bp;
      } else {
            dabuf->nbuf = nbuf;
            for (i = 0, dabuf->bbcount = 0; i < nbuf; i++) {
                  dabuf->bps[i] = bp = bps[i];
                  dabuf->bbcount += BTOBB(XFS_BUF_COUNT(bp));
            }
            dabuf->data = kmem_alloc(BBTOB(dabuf->bbcount), KM_SLEEP);
            for (i = off = 0; i < nbuf; i++, off += XFS_BUF_COUNT(bp)) {
                  bp = bps[i];
                  memcpy((char *)dabuf->data + off, XFS_BUF_PTR(bp),
                        XFS_BUF_COUNT(bp));
            }
      }
#ifdef XFS_DABUF_DEBUG
      {
            SPLDECL(s);
            xfs_dabuf_t *p;

            s = mutex_spinlock(&xfs_dabuf_global_lock);
            for (p = xfs_dabuf_global_list; p; p = p->next) {
                  ASSERT(p->blkno != dabuf->blkno ||
                         p->target != dabuf->target);
            }
            dabuf->prev = NULL;
            if (xfs_dabuf_global_list)
                  xfs_dabuf_global_list->prev = dabuf;
            dabuf->next = xfs_dabuf_global_list;
            xfs_dabuf_global_list = dabuf;
            mutex_spinunlock(&xfs_dabuf_global_lock, s);
      }
#endif
      return dabuf;
}

/*
 * Un-dirty a dabuf.
 */
STATIC void
xfs_da_buf_clean(xfs_dabuf_t *dabuf)
{
      xfs_buf_t   *bp;
      int         i;
      int         off;

      if (dabuf->dirty) {
            ASSERT(dabuf->nbuf > 1);
            dabuf->dirty = 0;
            for (i = off = 0; i < dabuf->nbuf;
                        i++, off += XFS_BUF_COUNT(bp)) {
                  bp = dabuf->bps[i];
                  memcpy(XFS_BUF_PTR(bp), (char *)dabuf->data + off,
                        XFS_BUF_COUNT(bp));
            }
      }
}

/*
 * Release a dabuf.
 */
void
xfs_da_buf_done(xfs_dabuf_t *dabuf)
{
      ASSERT(dabuf);
      ASSERT(dabuf->nbuf && dabuf->data && dabuf->bbcount && dabuf->bps[0]);
      if (dabuf->dirty)
            xfs_da_buf_clean(dabuf);
      if (dabuf->nbuf > 1)
            kmem_free(dabuf->data, BBTOB(dabuf->bbcount));
#ifdef XFS_DABUF_DEBUG
      {
            SPLDECL(s);

            s = mutex_spinlock(&xfs_dabuf_global_lock);
            if (dabuf->prev)
                  dabuf->prev->next = dabuf->next;
            else
                  xfs_dabuf_global_list = dabuf->next;
            if (dabuf->next)
                  dabuf->next->prev = dabuf->prev;
            mutex_spinunlock(&xfs_dabuf_global_lock, s);
      }
      memset(dabuf, 0, XFS_DA_BUF_SIZE(dabuf->nbuf));
#endif
      if (dabuf->nbuf == 1)
            kmem_zone_free(xfs_dabuf_zone, dabuf);
      else
            kmem_free(dabuf, XFS_DA_BUF_SIZE(dabuf->nbuf));
}

/*
 * Log transaction from a dabuf.
 */
void
xfs_da_log_buf(xfs_trans_t *tp, xfs_dabuf_t *dabuf, uint first, uint last)
{
      xfs_buf_t   *bp;
      uint        f;
      int         i;
      uint        l;
      int         off;

      ASSERT(dabuf->nbuf && dabuf->data && dabuf->bbcount && dabuf->bps[0]);
      if (dabuf->nbuf == 1) {
            ASSERT(dabuf->data == (void *)XFS_BUF_PTR(dabuf->bps[0]));
            xfs_trans_log_buf(tp, dabuf->bps[0], first, last);
            return;
      }
      dabuf->dirty = 1;
      ASSERT(first <= last);
      for (i = off = 0; i < dabuf->nbuf; i++, off += XFS_BUF_COUNT(bp)) {
            bp = dabuf->bps[i];
            f = off;
            l = f + XFS_BUF_COUNT(bp) - 1;
            if (f < first)
                  f = first;
            if (l > last)
                  l = last;
            if (f <= l)
                  xfs_trans_log_buf(tp, bp, f - off, l - off);
            /*
             * B_DONE is set by xfs_trans_log buf.
             * If we don't set it on a new buffer (get not read)
             * then if we don't put anything in the buffer it won't
             * be set, and at commit it it released into the cache,
             * and then a read will fail.
             */
            else if (!(XFS_BUF_ISDONE(bp)))
              XFS_BUF_DONE(bp);
      }
      ASSERT(last < off);
}

/*
 * Release dabuf from a transaction.
 * Have to free up the dabuf before the buffers are released,
 * since the synchronization on the dabuf is really the lock on the buffer.
 */
void
xfs_da_brelse(xfs_trans_t *tp, xfs_dabuf_t *dabuf)
{
      xfs_buf_t   *bp;
      xfs_buf_t   **bplist;
      int         i;
      int         nbuf;

      ASSERT(dabuf->nbuf && dabuf->data && dabuf->bbcount && dabuf->bps[0]);
      if ((nbuf = dabuf->nbuf) == 1) {
            bplist = &bp;
            bp = dabuf->bps[0];
      } else {
            bplist = kmem_alloc(nbuf * sizeof(*bplist), KM_SLEEP);
            memcpy(bplist, dabuf->bps, nbuf * sizeof(*bplist));
      }
      xfs_da_buf_done(dabuf);
      for (i = 0; i < nbuf; i++)
            xfs_trans_brelse(tp, bplist[i]);
      if (bplist != &bp)
            kmem_free(bplist, nbuf * sizeof(*bplist));
}

/*
 * Invalidate dabuf from a transaction.
 */
void
xfs_da_binval(xfs_trans_t *tp, xfs_dabuf_t *dabuf)
{
      xfs_buf_t   *bp;
      xfs_buf_t   **bplist;
      int         i;
      int         nbuf;

      ASSERT(dabuf->nbuf && dabuf->data && dabuf->bbcount && dabuf->bps[0]);
      if ((nbuf = dabuf->nbuf) == 1) {
            bplist = &bp;
            bp = dabuf->bps[0];
      } else {
            bplist = kmem_alloc(nbuf * sizeof(*bplist), KM_SLEEP);
            memcpy(bplist, dabuf->bps, nbuf * sizeof(*bplist));
      }
      xfs_da_buf_done(dabuf);
      for (i = 0; i < nbuf; i++)
            xfs_trans_binval(tp, bplist[i]);
      if (bplist != &bp)
            kmem_free(bplist, nbuf * sizeof(*bplist));
}

/*
 * Get the first daddr from a dabuf.
 */
xfs_daddr_t
xfs_da_blkno(xfs_dabuf_t *dabuf)
{
      ASSERT(dabuf->nbuf);
      ASSERT(dabuf->data);
      return XFS_BUF_ADDR(dabuf->bps[0]);
}

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