/*
   * btree.c - NILFS B-tree.
   *
   * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
   *
   * 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; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will 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 to the Free Software
   * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
   *
   * Written by Koji Sato <koji@osrg.net>.
   */
  
  #include <linux/slab.h>
  #include <linux/string.h>
  #include <linux/errno.h>
  #include <linux/pagevec.h>
  #include "nilfs.h"
  #include "page.h"
  #include "btnode.h"
  #include "btree.h"
  #include "alloc.h"

  #include "dat.h"

  static struct nilfs_btree_path *nilfs_btree_alloc_path(void)

  {

  	struct nilfs_btree_path *path;
  	int level = NILFS_BTREE_LEVEL_DATA;

  	path = kmem_cache_alloc(nilfs_btree_path_cache, GFP_NOFS);
  	if (path == NULL)
  		goto out;

  	for (; level < NILFS_BTREE_LEVEL_MAX; level++) {

  		path[level].bp_bh = NULL;
  		path[level].bp_sib_bh = NULL;
  		path[level].bp_index = 0;
  		path[level].bp_oldreq.bpr_ptr = NILFS_BMAP_INVALID_PTR;
  		path[level].bp_newreq.bpr_ptr = NILFS_BMAP_INVALID_PTR;
  		path[level].bp_op = NULL;
  	}

  
  out:
  	return path;
  }

  static void nilfs_btree_free_path(struct nilfs_btree_path *path)

  {

  	int level = NILFS_BTREE_LEVEL_DATA;

  	for (; level < NILFS_BTREE_LEVEL_MAX; level++)

  		brelse(path[level].bp_bh);

  
  	kmem_cache_free(nilfs_btree_path_cache, path);

  }

  /*
   * B-tree node operations
   */

  static int nilfs_btree_get_new_block(const struct nilfs_bmap *btree,

  				     __u64 ptr, struct buffer_head **bhp)
  {

  	struct address_space *btnc = &NILFS_BMAP_I(btree)->i_btnode_cache;

  	struct buffer_head *bh;

  	bh = nilfs_btnode_create_block(btnc, ptr);
  	if (!bh)
  		return -ENOMEM;
  
  	set_buffer_nilfs_volatile(bh);
  	*bhp = bh;
  	return 0;

  }

  static int nilfs_btree_node_get_flags(const struct nilfs_btree_node *node)

  {
  	return node->bn_flags;
  }

  static void

  nilfs_btree_node_set_flags(struct nilfs_btree_node *node, int flags)

  {
  	node->bn_flags = flags;
  }

  static int nilfs_btree_node_root(const struct nilfs_btree_node *node)

  {

  	return nilfs_btree_node_get_flags(node) & NILFS_BTREE_NODE_ROOT;

  }

  static int nilfs_btree_node_get_level(const struct nilfs_btree_node *node)

  {
  	return node->bn_level;
  }

  static void

  nilfs_btree_node_set_level(struct nilfs_btree_node *node, int level)

  {
  	node->bn_level = level;
  }

  static int nilfs_btree_node_get_nchildren(const struct nilfs_btree_node *node)

  {
  	return le16_to_cpu(node->bn_nchildren);
  }

  static void

  nilfs_btree_node_set_nchildren(struct nilfs_btree_node *node, int nchildren)

  {
  	node->bn_nchildren = cpu_to_le16(nchildren);
  }

  static int nilfs_btree_node_size(const struct nilfs_bmap *btree)

  {

  	return 1 << btree->b_inode->i_blkbits;

  }

  static int nilfs_btree_nchildren_per_block(const struct nilfs_bmap *btree)

  {

  	return btree->b_nchildren_per_block;

  }

  static __le64 *

  nilfs_btree_node_dkeys(const struct nilfs_btree_node *node)

  {
  	return (__le64 *)((char *)(node + 1) +

  			  (nilfs_btree_node_root(node) ?

  			   0 : NILFS_BTREE_NODE_EXTRA_PAD_SIZE));
  }

  static __le64 *

  nilfs_btree_node_dptrs(const struct nilfs_btree_node *node, int ncmax)

  {

  	return (__le64 *)(nilfs_btree_node_dkeys(node) + ncmax);

  }

  static __u64

  nilfs_btree_node_get_key(const struct nilfs_btree_node *node, int index)

  {

  	return le64_to_cpu(*(nilfs_btree_node_dkeys(node) + index));

  }

  static void

  nilfs_btree_node_set_key(struct nilfs_btree_node *node, int index, __u64 key)

  {

  	*(nilfs_btree_node_dkeys(node) + index) = cpu_to_le64(key);

  }

  static __u64

  nilfs_btree_node_get_ptr(const struct nilfs_btree_node *node, int index,
  			 int ncmax)

  {

  	return le64_to_cpu(*(nilfs_btree_node_dptrs(node, ncmax) + index));

  }

  static void

  nilfs_btree_node_set_ptr(struct nilfs_btree_node *node, int index, __u64 ptr,
  			 int ncmax)

  {

  	*(nilfs_btree_node_dptrs(node, ncmax) + index) = cpu_to_le64(ptr);

  }

  static void nilfs_btree_node_init(struct nilfs_btree_node *node, int flags,
  				  int level, int nchildren, int ncmax,

  				  const __u64 *keys, const __u64 *ptrs)
  {
  	__le64 *dkeys;
  	__le64 *dptrs;
  	int i;

  	nilfs_btree_node_set_flags(node, flags);
  	nilfs_btree_node_set_level(node, level);
  	nilfs_btree_node_set_nchildren(node, nchildren);

  	dkeys = nilfs_btree_node_dkeys(node);

  	dptrs = nilfs_btree_node_dptrs(node, ncmax);

  	for (i = 0; i < nchildren; i++) {

  		dkeys[i] = cpu_to_le64(keys[i]);
  		dptrs[i] = cpu_to_le64(ptrs[i]);

  	}
  }
  
  /* Assume the buffer heads corresponding to left and right are locked. */

  static void nilfs_btree_node_move_left(struct nilfs_btree_node *left,

  				       struct nilfs_btree_node *right,

  				       int n, int lncmax, int rncmax)

  {
  	__le64 *ldkeys, *rdkeys;
  	__le64 *ldptrs, *rdptrs;
  	int lnchildren, rnchildren;

  	ldkeys = nilfs_btree_node_dkeys(left);

  	ldptrs = nilfs_btree_node_dptrs(left, lncmax);

  	lnchildren = nilfs_btree_node_get_nchildren(left);

  	rdkeys = nilfs_btree_node_dkeys(right);

  	rdptrs = nilfs_btree_node_dptrs(right, rncmax);

  	rnchildren = nilfs_btree_node_get_nchildren(right);

  
  	memcpy(ldkeys + lnchildren, rdkeys, n * sizeof(*rdkeys));
  	memcpy(ldptrs + lnchildren, rdptrs, n * sizeof(*rdptrs));
  	memmove(rdkeys, rdkeys + n, (rnchildren - n) * sizeof(*rdkeys));
  	memmove(rdptrs, rdptrs + n, (rnchildren - n) * sizeof(*rdptrs));
  
  	lnchildren += n;
  	rnchildren -= n;

  	nilfs_btree_node_set_nchildren(left, lnchildren);
  	nilfs_btree_node_set_nchildren(right, rnchildren);

  }
  
  /* Assume that the buffer heads corresponding to left and right are locked. */

  static void nilfs_btree_node_move_right(struct nilfs_btree_node *left,

  					struct nilfs_btree_node *right,

  					int n, int lncmax, int rncmax)

  {
  	__le64 *ldkeys, *rdkeys;
  	__le64 *ldptrs, *rdptrs;
  	int lnchildren, rnchildren;

  	ldkeys = nilfs_btree_node_dkeys(left);

  	ldptrs = nilfs_btree_node_dptrs(left, lncmax);

  	lnchildren = nilfs_btree_node_get_nchildren(left);

  	rdkeys = nilfs_btree_node_dkeys(right);

  	rdptrs = nilfs_btree_node_dptrs(right, rncmax);

  	rnchildren = nilfs_btree_node_get_nchildren(right);

  
  	memmove(rdkeys + n, rdkeys, rnchildren * sizeof(*rdkeys));
  	memmove(rdptrs + n, rdptrs, rnchildren * sizeof(*rdptrs));
  	memcpy(rdkeys, ldkeys + lnchildren - n, n * sizeof(*rdkeys));
  	memcpy(rdptrs, ldptrs + lnchildren - n, n * sizeof(*rdptrs));
  
  	lnchildren -= n;
  	rnchildren += n;

  	nilfs_btree_node_set_nchildren(left, lnchildren);
  	nilfs_btree_node_set_nchildren(right, rnchildren);

  }
  
  /* Assume that the buffer head corresponding to node is locked. */

  static void nilfs_btree_node_insert(struct nilfs_btree_node *node, int index,
  				    __u64 key, __u64 ptr, int ncmax)

  {
  	__le64 *dkeys;
  	__le64 *dptrs;
  	int nchildren;

  	dkeys = nilfs_btree_node_dkeys(node);

  	dptrs = nilfs_btree_node_dptrs(node, ncmax);

  	nchildren = nilfs_btree_node_get_nchildren(node);

  	if (index < nchildren) {
  		memmove(dkeys + index + 1, dkeys + index,
  			(nchildren - index) * sizeof(*dkeys));
  		memmove(dptrs + index + 1, dptrs + index,
  			(nchildren - index) * sizeof(*dptrs));
  	}

  	dkeys[index] = cpu_to_le64(key);
  	dptrs[index] = cpu_to_le64(ptr);

  	nchildren++;

  	nilfs_btree_node_set_nchildren(node, nchildren);

  }
  
  /* Assume that the buffer head corresponding to node is locked. */

  static void nilfs_btree_node_delete(struct nilfs_btree_node *node, int index,
  				    __u64 *keyp, __u64 *ptrp, int ncmax)

  {
  	__u64 key;
  	__u64 ptr;
  	__le64 *dkeys;
  	__le64 *dptrs;
  	int nchildren;

  	dkeys = nilfs_btree_node_dkeys(node);

  	dptrs = nilfs_btree_node_dptrs(node, ncmax);

  	key = le64_to_cpu(dkeys[index]);
  	ptr = le64_to_cpu(dptrs[index]);

  	nchildren = nilfs_btree_node_get_nchildren(node);

  	if (keyp != NULL)
  		*keyp = key;
  	if (ptrp != NULL)
  		*ptrp = ptr;
  
  	if (index < nchildren - 1) {
  		memmove(dkeys + index, dkeys + index + 1,
  			(nchildren - index - 1) * sizeof(*dkeys));
  		memmove(dptrs + index, dptrs + index + 1,
  			(nchildren - index - 1) * sizeof(*dptrs));
  	}
  	nchildren--;

  	nilfs_btree_node_set_nchildren(node, nchildren);

  }

  static int nilfs_btree_node_lookup(const struct nilfs_btree_node *node,

  				   __u64 key, int *indexp)
  {
  	__u64 nkey;
  	int index, low, high, s;
  
  	/* binary search */
  	low = 0;

  	high = nilfs_btree_node_get_nchildren(node) - 1;

  	index = 0;
  	s = 0;
  	while (low <= high) {
  		index = (low + high) / 2;

  		nkey = nilfs_btree_node_get_key(node, index);

  		if (nkey == key) {
  			s = 0;
  			goto out;
  		} else if (nkey < key) {
  			low = index + 1;
  			s = -1;
  		} else {
  			high = index - 1;
  			s = 1;
  		}
  	}
  
  	/* adjust index */

  	if (nilfs_btree_node_get_level(node) > NILFS_BTREE_LEVEL_NODE_MIN) {
  		if (s > 0 && index > 0)

  			index--;
  	} else if (s < 0)
  		index++;
  
   out:

  	*indexp = index;
  
  	return s == 0;
  }

  /**
   * nilfs_btree_node_broken - verify consistency of btree node
   * @node: btree node block to be examined
   * @size: node size (in bytes)
   * @blocknr: block number
   *
   * Return Value: If node is broken, 1 is returned. Otherwise, 0 is returned.
   */
  static int nilfs_btree_node_broken(const struct nilfs_btree_node *node,
  				   size_t size, sector_t blocknr)
  {
  	int level, flags, nchildren;
  	int ret = 0;
  
  	level = nilfs_btree_node_get_level(node);
  	flags = nilfs_btree_node_get_flags(node);
  	nchildren = nilfs_btree_node_get_nchildren(node);
  
  	if (unlikely(level < NILFS_BTREE_LEVEL_NODE_MIN ||
  		     level >= NILFS_BTREE_LEVEL_MAX ||
  		     (flags & NILFS_BTREE_NODE_ROOT) ||
  		     nchildren < 0 ||
  		     nchildren > NILFS_BTREE_NODE_NCHILDREN_MAX(size))) {
  		printk(KERN_CRIT "NILFS: bad btree node (blocknr=%llu): "
  		       "level = %d, flags = 0x%x, nchildren = %d
  ",
  		       (unsigned long long)blocknr, level, flags, nchildren);
  		ret = 1;
  	}
  	return ret;
  }
  
  int nilfs_btree_broken_node_block(struct buffer_head *bh)
  {

  	int ret;
  
  	if (buffer_nilfs_checked(bh))
  		return 0;
  
  	ret = nilfs_btree_node_broken((struct nilfs_btree_node *)bh->b_data,

  				       bh->b_size, bh->b_blocknr);

  	if (likely(!ret))
  		set_buffer_nilfs_checked(bh);
  	return ret;

  }

  static struct nilfs_btree_node *

  nilfs_btree_get_root(const struct nilfs_bmap *btree)

  {

  	return (struct nilfs_btree_node *)btree->b_u.u_data;

  }

  static struct nilfs_btree_node *

  nilfs_btree_get_nonroot_node(const struct nilfs_btree_path *path, int level)

  {
  	return (struct nilfs_btree_node *)path[level].bp_bh->b_data;
  }

  static struct nilfs_btree_node *

  nilfs_btree_get_sib_node(const struct nilfs_btree_path *path, int level)

  {
  	return (struct nilfs_btree_node *)path[level].bp_sib_bh->b_data;
  }

  static int nilfs_btree_height(const struct nilfs_bmap *btree)

  {

  	return nilfs_btree_node_get_level(nilfs_btree_get_root(btree)) + 1;

  }

  static struct nilfs_btree_node *

  nilfs_btree_get_node(const struct nilfs_bmap *btree,

  		     const struct nilfs_btree_path *path,

  		     int level, int *ncmaxp)

  {

  	struct nilfs_btree_node *node;
  
  	if (level == nilfs_btree_height(btree) - 1) {
  		node = nilfs_btree_get_root(btree);
  		*ncmaxp = NILFS_BTREE_ROOT_NCHILDREN_MAX;
  	} else {
  		node = nilfs_btree_get_nonroot_node(path, level);
  		*ncmaxp = nilfs_btree_nchildren_per_block(btree);
  	}
  	return node;

  }

  static int

  nilfs_btree_bad_node(struct nilfs_btree_node *node, int level)
  {
  	if (unlikely(nilfs_btree_node_get_level(node) != level)) {
  		dump_stack();
  		printk(KERN_CRIT "NILFS: btree level mismatch: %d != %d
  ",
  		       nilfs_btree_node_get_level(node), level);
  		return 1;
  	}
  	return 0;
  }

  struct nilfs_btree_readahead_info {
  	struct nilfs_btree_node *node;	/* parent node */
  	int max_ra_blocks;		/* max nof blocks to read ahead */
  	int index;			/* current index on the parent node */
  	int ncmax;			/* nof children in the parent node */
  };
  
  static int __nilfs_btree_get_block(const struct nilfs_bmap *btree, __u64 ptr,
  				   struct buffer_head **bhp,
  				   const struct nilfs_btree_readahead_info *ra)
  {
  	struct address_space *btnc = &NILFS_BMAP_I(btree)->i_btnode_cache;
  	struct buffer_head *bh, *ra_bh;
  	sector_t submit_ptr = 0;
  	int ret;
  
  	ret = nilfs_btnode_submit_block(btnc, ptr, 0, READ, &bh, &submit_ptr);
  	if (ret) {
  		if (ret != -EEXIST)
  			return ret;
  		goto out_check;
  	}
  
  	if (ra) {
  		int i, n;
  		__u64 ptr2;
  
  		/* read ahead sibling nodes */
  		for (n = ra->max_ra_blocks, i = ra->index + 1;
  		     n > 0 && i < ra->ncmax; n--, i++) {
  			ptr2 = nilfs_btree_node_get_ptr(ra->node, i, ra->ncmax);
  
  			ret = nilfs_btnode_submit_block(btnc, ptr2, 0, READA,
  							&ra_bh, &submit_ptr);
  			if (likely(!ret || ret == -EEXIST))
  				brelse(ra_bh);
  			else if (ret != -EBUSY)
  				break;
  			if (!buffer_locked(bh))
  				goto out_no_wait;
  		}
  	}
  
  	wait_on_buffer(bh);
  
   out_no_wait:
  	if (!buffer_uptodate(bh)) {
  		brelse(bh);
  		return -EIO;
  	}
  
   out_check:
  	if (nilfs_btree_broken_node_block(bh)) {
  		clear_buffer_uptodate(bh);
  		brelse(bh);
  		return -EINVAL;
  	}
  
  	*bhp = bh;
  	return 0;
  }
  
  static int nilfs_btree_get_block(const struct nilfs_bmap *btree, __u64 ptr,
  				   struct buffer_head **bhp)
  {
  	return __nilfs_btree_get_block(btree, ptr, bhp, NULL);
  }

  static int nilfs_btree_do_lookup(const struct nilfs_bmap *btree,

  				 struct nilfs_btree_path *path,

  				 __u64 key, __u64 *ptrp, int minlevel,
  				 int readahead)

  {
  	struct nilfs_btree_node *node;

  	struct nilfs_btree_readahead_info p, *ra;

  	__u64 ptr;

  	int level, index, found, ncmax, ret;

  	node = nilfs_btree_get_root(btree);

  	level = nilfs_btree_node_get_level(node);
  	if (level < minlevel || nilfs_btree_node_get_nchildren(node) <= 0)

  		return -ENOENT;

  	found = nilfs_btree_node_lookup(node, key, &index);

  	ptr = nilfs_btree_node_get_ptr(node, index,
  				       NILFS_BTREE_ROOT_NCHILDREN_MAX);

  	path[level].bp_bh = NULL;
  	path[level].bp_index = index;

  	ncmax = nilfs_btree_nchildren_per_block(btree);

  	while (--level >= minlevel) {
  		ra = NULL;
  		if (level == NILFS_BTREE_LEVEL_NODE_MIN && readahead) {
  			p.node = nilfs_btree_get_node(btree, path, level + 1,
  						      &p.ncmax);
  			p.index = index;
  			p.max_ra_blocks = 7;
  			ra = &p;
  		}
  		ret = __nilfs_btree_get_block(btree, ptr, &path[level].bp_bh,
  					      ra);

  		if (ret < 0)
  			return ret;

  		node = nilfs_btree_get_nonroot_node(path, level);

  		if (nilfs_btree_bad_node(node, level))
  			return -EINVAL;

  		if (!found)

  			found = nilfs_btree_node_lookup(node, key, &index);

  		else
  			index = 0;

  		if (index < ncmax) {

  			ptr = nilfs_btree_node_get_ptr(node, index, ncmax);

  		} else {

  			WARN_ON(found || level != NILFS_BTREE_LEVEL_NODE_MIN);

  			/* insert */
  			ptr = NILFS_BMAP_INVALID_PTR;
  		}
  		path[level].bp_index = index;
  	}
  	if (!found)
  		return -ENOENT;
  
  	if (ptrp != NULL)
  		*ptrp = ptr;
  
  	return 0;
  }

  static int nilfs_btree_do_lookup_last(const struct nilfs_bmap *btree,

  				      struct nilfs_btree_path *path,
  				      __u64 *keyp, __u64 *ptrp)
  {
  	struct nilfs_btree_node *node;
  	__u64 ptr;

  	int index, level, ncmax, ret;

  
  	node = nilfs_btree_get_root(btree);

  	index = nilfs_btree_node_get_nchildren(node) - 1;

  	if (index < 0)
  		return -ENOENT;

  	level = nilfs_btree_node_get_level(node);

  	ptr = nilfs_btree_node_get_ptr(node, index,
  				       NILFS_BTREE_ROOT_NCHILDREN_MAX);

  	path[level].bp_bh = NULL;
  	path[level].bp_index = index;

  	ncmax = nilfs_btree_nchildren_per_block(btree);

  
  	for (level--; level > 0; level--) {

  		ret = nilfs_btree_get_block(btree, ptr, &path[level].bp_bh);

  		if (ret < 0)
  			return ret;

  		node = nilfs_btree_get_nonroot_node(path, level);

  		if (nilfs_btree_bad_node(node, level))
  			return -EINVAL;

  		index = nilfs_btree_node_get_nchildren(node) - 1;

  		ptr = nilfs_btree_node_get_ptr(node, index, ncmax);

  		path[level].bp_index = index;
  	}
  
  	if (keyp != NULL)

  		*keyp = nilfs_btree_node_get_key(node, index);

  	if (ptrp != NULL)
  		*ptrp = ptr;
  
  	return 0;
  }

  static int nilfs_btree_lookup(const struct nilfs_bmap *btree,

  			      __u64 key, int level, __u64 *ptrp)
  {

  	struct nilfs_btree_path *path;

  	int ret;

  	path = nilfs_btree_alloc_path();

  	if (path == NULL)
  		return -ENOMEM;

  	ret = nilfs_btree_do_lookup(btree, path, key, ptrp, level, 0);

  	nilfs_btree_free_path(path);

  
  	return ret;
  }

  static int nilfs_btree_lookup_contig(const struct nilfs_bmap *btree,

  				     __u64 key, __u64 *ptrp, unsigned maxblocks)
  {

  	struct nilfs_btree_path *path;
  	struct nilfs_btree_node *node;
  	struct inode *dat = NULL;
  	__u64 ptr, ptr2;
  	sector_t blocknr;
  	int level = NILFS_BTREE_LEVEL_NODE_MIN;

  	int ret, cnt, index, maxlevel, ncmax;

  	struct nilfs_btree_readahead_info p;

  	path = nilfs_btree_alloc_path();

  	if (path == NULL)
  		return -ENOMEM;

  	ret = nilfs_btree_do_lookup(btree, path, key, &ptr, level, 1);

  	if (ret < 0)
  		goto out;

  	if (NILFS_BMAP_USE_VBN(btree)) {
  		dat = nilfs_bmap_get_dat(btree);

  		ret = nilfs_dat_translate(dat, ptr, &blocknr);
  		if (ret < 0)
  			goto out;
  		ptr = blocknr;
  	}
  	cnt = 1;
  	if (cnt == maxblocks)
  		goto end;
  
  	maxlevel = nilfs_btree_height(btree) - 1;

  	node = nilfs_btree_get_node(btree, path, level, &ncmax);

  	index = path[level].bp_index + 1;
  	for (;;) {

  		while (index < nilfs_btree_node_get_nchildren(node)) {
  			if (nilfs_btree_node_get_key(node, index) !=

  			    key + cnt)
  				goto end;

  			ptr2 = nilfs_btree_node_get_ptr(node, index, ncmax);

  			if (dat) {
  				ret = nilfs_dat_translate(dat, ptr2, &blocknr);
  				if (ret < 0)
  					goto out;
  				ptr2 = blocknr;
  			}
  			if (ptr2 != ptr + cnt || ++cnt == maxblocks)
  				goto end;
  			index++;
  			continue;
  		}
  		if (level == maxlevel)
  			break;
  
  		/* look-up right sibling node */

  		p.node = nilfs_btree_get_node(btree, path, level + 1, &p.ncmax);
  		p.index = path[level + 1].bp_index + 1;
  		p.max_ra_blocks = 7;
  		if (p.index >= nilfs_btree_node_get_nchildren(p.node) ||
  		    nilfs_btree_node_get_key(p.node, p.index) != key + cnt)

  			break;

  		ptr2 = nilfs_btree_node_get_ptr(p.node, p.index, p.ncmax);
  		path[level + 1].bp_index = p.index;

  
  		brelse(path[level].bp_bh);
  		path[level].bp_bh = NULL;

  
  		ret = __nilfs_btree_get_block(btree, ptr2, &path[level].bp_bh,
  					      &p);

  		if (ret < 0)
  			goto out;

  		node = nilfs_btree_get_nonroot_node(path, level);

  		ncmax = nilfs_btree_nchildren_per_block(btree);

  		index = 0;
  		path[level].bp_index = index;
  	}
   end:
  	*ptrp = ptr;
  	ret = cnt;
   out:

  	nilfs_btree_free_path(path);

  	return ret;
  }

  static void nilfs_btree_promote_key(struct nilfs_bmap *btree,

  				    struct nilfs_btree_path *path,
  				    int level, __u64 key)
  {
  	if (level < nilfs_btree_height(btree) - 1) {
  		do {

  			nilfs_btree_node_set_key(

  				nilfs_btree_get_nonroot_node(path, level),

  				path[level].bp_index, key);
  			if (!buffer_dirty(path[level].bp_bh))

  				mark_buffer_dirty(path[level].bp_bh);

  		} while ((path[level].bp_index == 0) &&
  			 (++level < nilfs_btree_height(btree) - 1));
  	}
  
  	/* root */
  	if (level == nilfs_btree_height(btree) - 1) {

  		nilfs_btree_node_set_key(nilfs_btree_get_root(btree),

  					 path[level].bp_index, key);
  	}
  }

  static void nilfs_btree_do_insert(struct nilfs_bmap *btree,

  				  struct nilfs_btree_path *path,
  				  int level, __u64 *keyp, __u64 *ptrp)
  {
  	struct nilfs_btree_node *node;

  	int ncblk;

  
  	if (level < nilfs_btree_height(btree) - 1) {

  		node = nilfs_btree_get_nonroot_node(path, level);

  		ncblk = nilfs_btree_nchildren_per_block(btree);
  		nilfs_btree_node_insert(node, path[level].bp_index,
  					*keyp, *ptrp, ncblk);

  		if (!buffer_dirty(path[level].bp_bh))

  			mark_buffer_dirty(path[level].bp_bh);

  
  		if (path[level].bp_index == 0)
  			nilfs_btree_promote_key(btree, path, level + 1,

  						nilfs_btree_node_get_key(node,
  									 0));

  	} else {
  		node = nilfs_btree_get_root(btree);

  		nilfs_btree_node_insert(node, path[level].bp_index,
  					*keyp, *ptrp,
  					NILFS_BTREE_ROOT_NCHILDREN_MAX);

  	}
  }

  static void nilfs_btree_carry_left(struct nilfs_bmap *btree,

  				   struct nilfs_btree_path *path,
  				   int level, __u64 *keyp, __u64 *ptrp)
  {
  	struct nilfs_btree_node *node, *left;

  	int nchildren, lnchildren, n, move, ncblk;

  	node = nilfs_btree_get_nonroot_node(path, level);
  	left = nilfs_btree_get_sib_node(path, level);
  	nchildren = nilfs_btree_node_get_nchildren(node);
  	lnchildren = nilfs_btree_node_get_nchildren(left);

  	ncblk = nilfs_btree_nchildren_per_block(btree);

  	move = 0;
  
  	n = (nchildren + lnchildren + 1) / 2 - lnchildren;
  	if (n > path[level].bp_index) {
  		/* move insert point */
  		n--;
  		move = 1;
  	}

  	nilfs_btree_node_move_left(left, node, n, ncblk, ncblk);

  
  	if (!buffer_dirty(path[level].bp_bh))

  		mark_buffer_dirty(path[level].bp_bh);

  	if (!buffer_dirty(path[level].bp_sib_bh))

  		mark_buffer_dirty(path[level].bp_sib_bh);

  	nilfs_btree_promote_key(btree, path, level + 1,

  				nilfs_btree_node_get_key(node, 0));

  
  	if (move) {

  		brelse(path[level].bp_bh);

  		path[level].bp_bh = path[level].bp_sib_bh;
  		path[level].bp_sib_bh = NULL;
  		path[level].bp_index += lnchildren;
  		path[level + 1].bp_index--;
  	} else {

  		brelse(path[level].bp_sib_bh);

  		path[level].bp_sib_bh = NULL;
  		path[level].bp_index -= n;
  	}
  
  	nilfs_btree_do_insert(btree, path, level, keyp, ptrp);
  }

  static void nilfs_btree_carry_right(struct nilfs_bmap *btree,

  				    struct nilfs_btree_path *path,
  				    int level, __u64 *keyp, __u64 *ptrp)
  {
  	struct nilfs_btree_node *node, *right;

  	int nchildren, rnchildren, n, move, ncblk;

  	node = nilfs_btree_get_nonroot_node(path, level);
  	right = nilfs_btree_get_sib_node(path, level);
  	nchildren = nilfs_btree_node_get_nchildren(node);
  	rnchildren = nilfs_btree_node_get_nchildren(right);

  	ncblk = nilfs_btree_nchildren_per_block(btree);

  	move = 0;
  
  	n = (nchildren + rnchildren + 1) / 2 - rnchildren;
  	if (n > nchildren - path[level].bp_index) {
  		/* move insert point */
  		n--;
  		move = 1;
  	}

  	nilfs_btree_node_move_right(node, right, n, ncblk, ncblk);

  
  	if (!buffer_dirty(path[level].bp_bh))

  		mark_buffer_dirty(path[level].bp_bh);

  	if (!buffer_dirty(path[level].bp_sib_bh))

  		mark_buffer_dirty(path[level].bp_sib_bh);

  	path[level + 1].bp_index++;
  	nilfs_btree_promote_key(btree, path, level + 1,

  				nilfs_btree_node_get_key(right, 0));

  	path[level + 1].bp_index--;
  
  	if (move) {

  		brelse(path[level].bp_bh);

  		path[level].bp_bh = path[level].bp_sib_bh;
  		path[level].bp_sib_bh = NULL;

  		path[level].bp_index -= nilfs_btree_node_get_nchildren(node);

  		path[level + 1].bp_index++;
  	} else {

  		brelse(path[level].bp_sib_bh);

  		path[level].bp_sib_bh = NULL;
  	}
  
  	nilfs_btree_do_insert(btree, path, level, keyp, ptrp);
  }

  static void nilfs_btree_split(struct nilfs_bmap *btree,

  			      struct nilfs_btree_path *path,
  			      int level, __u64 *keyp, __u64 *ptrp)
  {
  	struct nilfs_btree_node *node, *right;
  	__u64 newkey;
  	__u64 newptr;

  	int nchildren, n, move, ncblk;

  	node = nilfs_btree_get_nonroot_node(path, level);
  	right = nilfs_btree_get_sib_node(path, level);
  	nchildren = nilfs_btree_node_get_nchildren(node);

  	ncblk = nilfs_btree_nchildren_per_block(btree);

  	move = 0;
  
  	n = (nchildren + 1) / 2;
  	if (n > nchildren - path[level].bp_index) {
  		n--;
  		move = 1;
  	}

  	nilfs_btree_node_move_right(node, right, n, ncblk, ncblk);

  
  	if (!buffer_dirty(path[level].bp_bh))

  		mark_buffer_dirty(path[level].bp_bh);

  	if (!buffer_dirty(path[level].bp_sib_bh))

  		mark_buffer_dirty(path[level].bp_sib_bh);

  	newkey = nilfs_btree_node_get_key(right, 0);

  	newptr = path[level].bp_newreq.bpr_ptr;
  
  	if (move) {

  		path[level].bp_index -= nilfs_btree_node_get_nchildren(node);

  		nilfs_btree_node_insert(right, path[level].bp_index,
  					*keyp, *ptrp, ncblk);

  		*keyp = nilfs_btree_node_get_key(right, 0);

  		*ptrp = path[level].bp_newreq.bpr_ptr;

  		brelse(path[level].bp_bh);

  		path[level].bp_bh = path[level].bp_sib_bh;
  		path[level].bp_sib_bh = NULL;
  	} else {
  		nilfs_btree_do_insert(btree, path, level, keyp, ptrp);

  		*keyp = nilfs_btree_node_get_key(right, 0);

  		*ptrp = path[level].bp_newreq.bpr_ptr;

  		brelse(path[level].bp_sib_bh);

  		path[level].bp_sib_bh = NULL;
  	}
  
  	path[level + 1].bp_index++;
  }

  static void nilfs_btree_grow(struct nilfs_bmap *btree,

  			     struct nilfs_btree_path *path,
  			     int level, __u64 *keyp, __u64 *ptrp)
  {
  	struct nilfs_btree_node *root, *child;

  	int n, ncblk;

  	root = nilfs_btree_get_root(btree);

  	child = nilfs_btree_get_sib_node(path, level);

  	ncblk = nilfs_btree_nchildren_per_block(btree);

  	n = nilfs_btree_node_get_nchildren(root);

  	nilfs_btree_node_move_right(root, child, n,
  				    NILFS_BTREE_ROOT_NCHILDREN_MAX, ncblk);

  	nilfs_btree_node_set_level(root, level + 1);

  
  	if (!buffer_dirty(path[level].bp_sib_bh))

  		mark_buffer_dirty(path[level].bp_sib_bh);

  	path[level].bp_bh = path[level].bp_sib_bh;
  	path[level].bp_sib_bh = NULL;
  
  	nilfs_btree_do_insert(btree, path, level, keyp, ptrp);

  	*keyp = nilfs_btree_node_get_key(child, 0);

  	*ptrp = path[level].bp_newreq.bpr_ptr;
  }

  static __u64 nilfs_btree_find_near(const struct nilfs_bmap *btree,

  				   const struct nilfs_btree_path *path)
  {
  	struct nilfs_btree_node *node;

  	int level, ncmax;

  
  	if (path == NULL)
  		return NILFS_BMAP_INVALID_PTR;
  
  	/* left sibling */
  	level = NILFS_BTREE_LEVEL_NODE_MIN;
  	if (path[level].bp_index > 0) {

  		node = nilfs_btree_get_node(btree, path, level, &ncmax);
  		return nilfs_btree_node_get_ptr(node,
  						path[level].bp_index - 1,
  						ncmax);

  	}
  
  	/* parent */
  	level = NILFS_BTREE_LEVEL_NODE_MIN + 1;
  	if (level <= nilfs_btree_height(btree) - 1) {

  		node = nilfs_btree_get_node(btree, path, level, &ncmax);
  		return nilfs_btree_node_get_ptr(node, path[level].bp_index,
  						ncmax);

  	}
  
  	return NILFS_BMAP_INVALID_PTR;
  }

  static __u64 nilfs_btree_find_target_v(const struct nilfs_bmap *btree,

  				       const struct nilfs_btree_path *path,
  				       __u64 key)
  {
  	__u64 ptr;

  	ptr = nilfs_bmap_find_target_seq(btree, key);

  	if (ptr != NILFS_BMAP_INVALID_PTR)
  		/* sequential access */
  		return ptr;
  	else {
  		ptr = nilfs_btree_find_near(btree, path);
  		if (ptr != NILFS_BMAP_INVALID_PTR)
  			/* near */
  			return ptr;
  	}
  	/* block group */

  	return nilfs_bmap_find_target_in_group(btree);

  }

  static int nilfs_btree_prepare_insert(struct nilfs_bmap *btree,

  				      struct nilfs_btree_path *path,
  				      int *levelp, __u64 key, __u64 ptr,
  				      struct nilfs_bmap_stats *stats)
  {
  	struct buffer_head *bh;
  	struct nilfs_btree_node *node, *parent, *sib;
  	__u64 sibptr;

  	int pindex, level, ncmax, ncblk, ret;

  	struct inode *dat = NULL;

  
  	stats->bs_nblocks = 0;
  	level = NILFS_BTREE_LEVEL_DATA;
  
  	/* allocate a new ptr for data block */

  	if (NILFS_BMAP_USE_VBN(btree)) {

  		path[level].bp_newreq.bpr_ptr =

  			nilfs_btree_find_target_v(btree, path, key);

  		dat = nilfs_bmap_get_dat(btree);

  	}

  	ret = nilfs_bmap_prepare_alloc_ptr(btree, &path[level].bp_newreq, dat);

  	if (ret < 0)
  		goto err_out_data;

  	ncblk = nilfs_btree_nchildren_per_block(btree);

  	for (level = NILFS_BTREE_LEVEL_NODE_MIN;
  	     level < nilfs_btree_height(btree) - 1;
  	     level++) {

  		node = nilfs_btree_get_nonroot_node(path, level);

  		if (nilfs_btree_node_get_nchildren(node) < ncblk) {

  			path[level].bp_op = nilfs_btree_do_insert;
  			stats->bs_nblocks++;
  			goto out;
  		}

  		parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);

  		pindex = path[level + 1].bp_index;
  
  		/* left sibling */
  		if (pindex > 0) {

  			sibptr = nilfs_btree_node_get_ptr(parent, pindex - 1,
  							  ncmax);

  			ret = nilfs_btree_get_block(btree, sibptr, &bh);

  			if (ret < 0)
  				goto err_out_child_node;
  			sib = (struct nilfs_btree_node *)bh->b_data;

  			if (nilfs_btree_node_get_nchildren(sib) < ncblk) {

  				path[level].bp_sib_bh = bh;
  				path[level].bp_op = nilfs_btree_carry_left;
  				stats->bs_nblocks++;
  				goto out;

  			} else {

  				brelse(bh);

  			}

  		}
  
  		/* right sibling */

  		if (pindex < nilfs_btree_node_get_nchildren(parent) - 1) {
  			sibptr = nilfs_btree_node_get_ptr(parent, pindex + 1,
  							  ncmax);

  			ret = nilfs_btree_get_block(btree, sibptr, &bh);

  			if (ret < 0)
  				goto err_out_child_node;
  			sib = (struct nilfs_btree_node *)bh->b_data;

  			if (nilfs_btree_node_get_nchildren(sib) < ncblk) {

  				path[level].bp_sib_bh = bh;
  				path[level].bp_op = nilfs_btree_carry_right;
  				stats->bs_nblocks++;
  				goto out;

  			} else {

  				brelse(bh);

  			}

  		}
  
  		/* split */
  		path[level].bp_newreq.bpr_ptr =
  			path[level - 1].bp_newreq.bpr_ptr + 1;

  		ret = nilfs_bmap_prepare_alloc_ptr(btree,

  						   &path[level].bp_newreq, dat);

  		if (ret < 0)
  			goto err_out_child_node;

  		ret = nilfs_btree_get_new_block(btree,
  						path[level].bp_newreq.bpr_ptr,
  						&bh);

  		if (ret < 0)
  			goto err_out_curr_node;
  
  		stats->bs_nblocks++;

  		sib = (struct nilfs_btree_node *)bh->b_data;
  		nilfs_btree_node_init(sib, 0, level, 0, ncblk, NULL, NULL);

  		path[level].bp_sib_bh = bh;
  		path[level].bp_op = nilfs_btree_split;
  	}
  
  	/* root */
  	node = nilfs_btree_get_root(btree);

  	if (nilfs_btree_node_get_nchildren(node) <

  	    NILFS_BTREE_ROOT_NCHILDREN_MAX) {

  		path[level].bp_op = nilfs_btree_do_insert;
  		stats->bs_nblocks++;
  		goto out;
  	}
  
  	/* grow */
  	path[level].bp_newreq.bpr_ptr = path[level - 1].bp_newreq.bpr_ptr + 1;

  	ret = nilfs_bmap_prepare_alloc_ptr(btree, &path[level].bp_newreq, dat);

  	if (ret < 0)
  		goto err_out_child_node;

  	ret = nilfs_btree_get_new_block(btree, path[level].bp_newreq.bpr_ptr,
  					&bh);

  	if (ret < 0)
  		goto err_out_curr_node;

  	nilfs_btree_node_init((struct nilfs_btree_node *)bh->b_data,
  			      0, level, 0, ncblk, NULL, NULL);

  	path[level].bp_sib_bh = bh;
  	path[level].bp_op = nilfs_btree_grow;
  
  	level++;
  	path[level].bp_op = nilfs_btree_do_insert;
  
  	/* a newly-created node block and a data block are added */
  	stats->bs_nblocks += 2;
  
  	/* success */
   out:
  	*levelp = level;
  	return ret;
  
  	/* error */
   err_out_curr_node:

  	nilfs_bmap_abort_alloc_ptr(btree, &path[level].bp_newreq, dat);

   err_out_child_node:
  	for (level--; level > NILFS_BTREE_LEVEL_DATA; level--) {

  		nilfs_btnode_delete(path[level].bp_sib_bh);

  		nilfs_bmap_abort_alloc_ptr(btree, &path[level].bp_newreq, dat);

  
  	}

  	nilfs_bmap_abort_alloc_ptr(btree, &path[level].bp_newreq, dat);

   err_out_data:
  	*levelp = level;
  	stats->bs_nblocks = 0;
  	return ret;
  }

  static void nilfs_btree_commit_insert(struct nilfs_bmap *btree,

  				      struct nilfs_btree_path *path,
  				      int maxlevel, __u64 key, __u64 ptr)
  {

  	struct inode *dat = NULL;

  	int level;
  
  	set_buffer_nilfs_volatile((struct buffer_head *)((unsigned long)ptr));
  	ptr = path[NILFS_BTREE_LEVEL_DATA].bp_newreq.bpr_ptr;

  	if (NILFS_BMAP_USE_VBN(btree)) {

  		nilfs_bmap_set_target_v(btree, key, ptr);

  		dat = nilfs_bmap_get_dat(btree);

  	}

  
  	for (level = NILFS_BTREE_LEVEL_NODE_MIN; level <= maxlevel; level++) {

  		nilfs_bmap_commit_alloc_ptr(btree,

  					    &path[level - 1].bp_newreq, dat);

  		path[level].bp_op(btree, path, level, &key, &ptr);

  	}

  	if (!nilfs_bmap_dirty(btree))
  		nilfs_bmap_set_dirty(btree);

  }

  static int nilfs_btree_insert(struct nilfs_bmap *btree, __u64 key, __u64 ptr)

  {

  	struct nilfs_btree_path *path;
  	struct nilfs_bmap_stats stats;
  	int level, ret;

  	path = nilfs_btree_alloc_path();

  	if (path == NULL)
  		return -ENOMEM;

  
  	ret = nilfs_btree_do_lookup(btree, path, key, NULL,

  				    NILFS_BTREE_LEVEL_NODE_MIN, 0);

  	if (ret != -ENOENT) {
  		if (ret == 0)
  			ret = -EEXIST;
  		goto out;
  	}
  
  	ret = nilfs_btree_prepare_insert(btree, path, &level, key, ptr, &stats);
  	if (ret < 0)
  		goto out;
  	nilfs_btree_commit_insert(btree, path, level, key, ptr);

  	nilfs_inode_add_blocks(btree->b_inode, stats.bs_nblocks);

  
   out:

  	nilfs_btree_free_path(path);

  	return ret;
  }

  static void nilfs_btree_do_delete(struct nilfs_bmap *btree,

  				  struct nilfs_btree_path *path,
  				  int level, __u64 *keyp, __u64 *ptrp)
  {
  	struct nilfs_btree_node *node;

  	int ncblk;

  
  	if (level < nilfs_btree_height(btree) - 1) {

  		node = nilfs_btree_get_nonroot_node(path, level);

  		ncblk = nilfs_btree_nchildren_per_block(btree);
  		nilfs_btree_node_delete(node, path[level].bp_index,
  					keyp, ptrp, ncblk);

  		if (!buffer_dirty(path[level].bp_bh))

  			mark_buffer_dirty(path[level].bp_bh);

  		if (path[level].bp_index == 0)
  			nilfs_btree_promote_key(btree, path, level + 1,

  				nilfs_btree_node_get_key(node, 0));

  	} else {
  		node = nilfs_btree_get_root(btree);

  		nilfs_btree_node_delete(node, path[level].bp_index,
  					keyp, ptrp,
  					NILFS_BTREE_ROOT_NCHILDREN_MAX);

  	}
  }

  static void nilfs_btree_borrow_left(struct nilfs_bmap *btree,

  				    struct nilfs_btree_path *path,
  				    int level, __u64 *keyp, __u64 *ptrp)
  {
  	struct nilfs_btree_node *node, *left;

  	int nchildren, lnchildren, n, ncblk;

  
  	nilfs_btree_do_delete(btree, path, level, keyp, ptrp);

  	node = nilfs_btree_get_nonroot_node(path, level);
  	left = nilfs_btree_get_sib_node(path, level);
  	nchildren = nilfs_btree_node_get_nchildren(node);
  	lnchildren = nilfs_btree_node_get_nchildren(left);

  	ncblk = nilfs_btree_nchildren_per_block(btree);

  
  	n = (nchildren + lnchildren) / 2 - nchildren;

  	nilfs_btree_node_move_right(left, node, n, ncblk, ncblk);

  
  	if (!buffer_dirty(path[level].bp_bh))

  		mark_buffer_dirty(path[level].bp_bh);

  	if (!buffer_dirty(path[level].bp_sib_bh))

  		mark_buffer_dirty(path[level].bp_sib_bh);

  	nilfs_btree_promote_key(btree, path, level + 1,

  				nilfs_btree_node_get_key(node, 0));

  	brelse(path[level].bp_sib_bh);

  	path[level].bp_sib_bh = NULL;
  	path[level].bp_index += n;
  }

  static void nilfs_btree_borrow_right(struct nilfs_bmap *btree,

  				     struct nilfs_btree_path *path,
  				     int level, __u64 *keyp, __u64 *ptrp)
  {
  	struct nilfs_btree_node *node, *right;

  	int nchildren, rnchildren, n, ncblk;

  
  	nilfs_btree_do_delete(btree, path, level, keyp, ptrp);

  	node = nilfs_btree_get_nonroot_node(path, level);
  	right = nilfs_btree_get_sib_node(path, level);
  	nchildren = nilfs_btree_node_get_nchildren(node);
  	rnchildren = nilfs_btree_node_get_nchildren(right);

  	ncblk = nilfs_btree_nchildren_per_block(btree);

  
  	n = (nchildren + rnchildren) / 2 - nchildren;

  	nilfs_btree_node_move_left(node, right, n, ncblk, ncblk);

  
  	if (!buffer_dirty(path[level].bp_bh))

  		mark_buffer_dirty(path[level].bp_bh);

  	if (!buffer_dirty(path[level].bp_sib_bh))

  		mark_buffer_dirty(path[level].bp_sib_bh);

  	path[level + 1].bp_index++;
  	nilfs_btree_promote_key(btree, path, level + 1,

  				nilfs_btree_node_get_key(right, 0));

  	path[level + 1].bp_index--;

  	brelse(path[level].bp_sib_bh);

  	path[level].bp_sib_bh = NULL;
  }

  static void nilfs_btree_concat_left(struct nilfs_bmap *btree,

  				    struct nilfs_btree_path *path,
  				    int level, __u64 *keyp, __u64 *ptrp)
  {
  	struct nilfs_btree_node *node, *left;

  	int n, ncblk;

  
  	nilfs_btree_do_delete(btree, path, level, keyp, ptrp);

  	node = nilfs_btree_get_nonroot_node(path, level);
  	left = nilfs_btree_get_sib_node(path, level);

  	ncblk = nilfs_btree_nchildren_per_block(btree);

  	n = nilfs_btree_node_get_nchildren(node);

  	nilfs_btree_node_move_left(left, node, n, ncblk, ncblk);

  
  	if (!buffer_dirty(path[level].bp_sib_bh))

  		mark_buffer_dirty(path[level].bp_sib_bh);

  	nilfs_btnode_delete(path[level].bp_bh);

  	path[level].bp_bh = path[level].bp_sib_bh;
  	path[level].bp_sib_bh = NULL;

  	path[level].bp_index += nilfs_btree_node_get_nchildren(left);

  }

  static void nilfs_btree_concat_right(struct nilfs_bmap *btree,

  				     struct nilfs_btree_path *path,
  				     int level, __u64 *keyp, __u64 *ptrp)
  {
  	struct nilfs_btree_node *node, *right;

  	int n, ncblk;

  
  	nilfs_btree_do_delete(btree, path, level, keyp, ptrp);

  	node = nilfs_btree_get_nonroot_node(path, level);
  	right = nilfs_btree_get_sib_node(path, level);

  	ncblk = nilfs_btree_nchildren_per_block(btree);

  	n = nilfs_btree_node_get_nchildren(right);

  	nilfs_btree_node_move_left(node, right, n, ncblk, ncblk);

  
  	if (!buffer_dirty(path[level].bp_bh))

  		mark_buffer_dirty(path[level].bp_bh);

  	nilfs_btnode_delete(path[level].bp_sib_bh);

  	path[level].bp_sib_bh = NULL;
  	path[level + 1].bp_index++;
  }

  static void nilfs_btree_shrink(struct nilfs_bmap *btree,

  			       struct nilfs_btree_path *path,
  			       int level, __u64 *keyp, __u64 *ptrp)
  {
  	struct nilfs_btree_node *root, *child;

  	int n, ncblk;

  
  	nilfs_btree_do_delete(btree, path, level, keyp, ptrp);

  	root = nilfs_btree_get_root(btree);

  	child = nilfs_btree_get_nonroot_node(path, level);

  	ncblk = nilfs_btree_nchildren_per_block(btree);

  	nilfs_btree_node_delete(root, 0, NULL, NULL,
  				NILFS_BTREE_ROOT_NCHILDREN_MAX);

  	nilfs_btree_node_set_level(root, level);
  	n = nilfs_btree_node_get_nchildren(child);

  	nilfs_btree_node_move_left(root, child, n,
  				   NILFS_BTREE_ROOT_NCHILDREN_MAX, ncblk);

  	nilfs_btnode_delete(path[level].bp_bh);

  	path[level].bp_bh = NULL;
  }

  static void nilfs_btree_nop(struct nilfs_bmap *btree,
  			    struct nilfs_btree_path *path,
  			    int level, __u64 *keyp, __u64 *ptrp)
  {
  }

  static int nilfs_btree_prepare_delete(struct nilfs_bmap *btree,

  				      struct nilfs_btree_path *path,
  				      int *levelp,

  				      struct nilfs_bmap_stats *stats,
  				      struct inode *dat)

  {
  	struct buffer_head *bh;
  	struct nilfs_btree_node *node, *parent, *sib;
  	__u64 sibptr;

  	int pindex, dindex, level, ncmin, ncmax, ncblk, ret;

  
  	ret = 0;
  	stats->bs_nblocks = 0;

  	ncmin = NILFS_BTREE_NODE_NCHILDREN_MIN(nilfs_btree_node_size(btree));

  	ncblk = nilfs_btree_nchildren_per_block(btree);

  	for (level = NILFS_BTREE_LEVEL_NODE_MIN, dindex = path[level].bp_index;

  	     level < nilfs_btree_height(btree) - 1;
  	     level++) {

  		node = nilfs_btree_get_nonroot_node(path, level);

  		path[level].bp_oldreq.bpr_ptr =

  			nilfs_btree_node_get_ptr(node, dindex, ncblk);

  		ret = nilfs_bmap_prepare_end_ptr(btree,

  						 &path[level].bp_oldreq, dat);

  		if (ret < 0)
  			goto err_out_child_node;

  		if (nilfs_btree_node_get_nchildren(node) > ncmin) {

  			path[level].bp_op = nilfs_btree_do_delete;
  			stats->bs_nblocks++;
  			goto out;
  		}

  		parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);

  		pindex = path[level + 1].bp_index;

  		dindex = pindex;

  
  		if (pindex > 0) {
  			/* left sibling */

  			sibptr = nilfs_btree_node_get_ptr(parent, pindex - 1,
  							  ncmax);

  			ret = nilfs_btree_get_block(btree, sibptr, &bh);

  			if (ret < 0)
  				goto err_out_curr_node;
  			sib = (struct nilfs_btree_node *)bh->b_data;

  			if (nilfs_btree_node_get_nchildren(sib) > ncmin) {

  				path[level].bp_sib_bh = bh;
  				path[level].bp_op = nilfs_btree_borrow_left;
  				stats->bs_nblocks++;
  				goto out;
  			} else {
  				path[level].bp_sib_bh = bh;
  				path[level].bp_op = nilfs_btree_concat_left;
  				stats->bs_nblocks++;
  				/* continue; */
  			}
  		} else if (pindex <

  			   nilfs_btree_node_get_nchildren(parent) - 1) {

  			/* right sibling */

  			sibptr = nilfs_btree_node_get_ptr(parent, pindex + 1,
  							  ncmax);

  			ret = nilfs_btree_get_block(btree, sibptr, &bh);

  			if (ret < 0)
  				goto err_out_curr_node;
  			sib = (struct nilfs_btree_node *)bh->b_data;

  			if (nilfs_btree_node_get_nchildren(sib) > ncmin) {

  				path[level].bp_sib_bh = bh;
  				path[level].bp_op = nilfs_btree_borrow_right;
  				stats->bs_nblocks++;
  				goto out;
  			} else {
  				path[level].bp_sib_bh = bh;
  				path[level].bp_op = nilfs_btree_concat_right;
  				stats->bs_nblocks++;

  				/*
  				 * When merging right sibling node
  				 * into the current node, pointer to
  				 * the right sibling node must be
  				 * terminated instead.  The adjustment
  				 * below is required for that.
  				 */
  				dindex = pindex + 1;

  				/* continue; */
  			}
  		} else {
  			/* no siblings */
  			/* the only child of the root node */

  			WARN_ON(level != nilfs_btree_height(btree) - 2);

  			if (nilfs_btree_node_get_nchildren(node) - 1 <=

  			    NILFS_BTREE_ROOT_NCHILDREN_MAX) {
  				path[level].bp_op = nilfs_btree_shrink;
  				stats->bs_nblocks += 2;

  				level++;
  				path[level].bp_op = nilfs_btree_nop;
  				goto shrink_root_child;

  			} else {
  				path[level].bp_op = nilfs_btree_do_delete;
  				stats->bs_nblocks++;

  				goto out;

  			}

  		}
  	}

  	/* child of the root node is deleted */
  	path[level].bp_op = nilfs_btree_do_delete;
  	stats->bs_nblocks++;
  
  shrink_root_child:

  	node = nilfs_btree_get_root(btree);
  	path[level].bp_oldreq.bpr_ptr =

  		nilfs_btree_node_get_ptr(node, dindex,

  					 NILFS_BTREE_ROOT_NCHILDREN_MAX);

  	ret = nilfs_bmap_prepare_end_ptr(btree, &path[level].bp_oldreq, dat);

  	if (ret < 0)
  		goto err_out_child_node;

  	/* success */
   out:
  	*levelp = level;
  	return ret;
  
  	/* error */
   err_out_curr_node:

  	nilfs_bmap_abort_end_ptr(btree, &path[level].bp_oldreq, dat);

   err_out_child_node:
  	for (level--; level >= NILFS_BTREE_LEVEL_NODE_MIN; level--) {

  		brelse(path[level].bp_sib_bh);

  		nilfs_bmap_abort_end_ptr(btree, &path[level].bp_oldreq, dat);

  	}
  	*levelp = level;
  	stats->bs_nblocks = 0;
  	return ret;
  }

  static void nilfs_btree_commit_delete(struct nilfs_bmap *btree,

  				      struct nilfs_btree_path *path,

  				      int maxlevel, struct inode *dat)

  {
  	int level;
  
  	for (level = NILFS_BTREE_LEVEL_NODE_MIN; level <= maxlevel; level++) {

  		nilfs_bmap_commit_end_ptr(btree, &path[level].bp_oldreq, dat);

  		path[level].bp_op(btree, path, level, NULL, NULL);

  	}

  	if (!nilfs_bmap_dirty(btree))
  		nilfs_bmap_set_dirty(btree);

  }

  static int nilfs_btree_delete(struct nilfs_bmap *btree, __u64 key)

  
  {

  	struct nilfs_btree_path *path;
  	struct nilfs_bmap_stats stats;

  	struct inode *dat;

  	int level, ret;

  	path = nilfs_btree_alloc_path();

  	if (path == NULL)
  		return -ENOMEM;

  	ret = nilfs_btree_do_lookup(btree, path, key, NULL,

  				    NILFS_BTREE_LEVEL_NODE_MIN, 0);

  	if (ret < 0)
  		goto out;

  	dat = NILFS_BMAP_USE_VBN(btree) ? nilfs_bmap_get_dat(btree) : NULL;

  
  	ret = nilfs_btree_prepare_delete(btree, path, &level, &stats, dat);

  	if (ret < 0)
  		goto out;

  	nilfs_btree_commit_delete(btree, path, level, dat);