nilfs2: B-tree based block mapping

This adds declarations and functions of NILFS2 B-tree.

Two variants are integrated in the NILFS2 B-tree.  The B-tree for the most
files points to the child nodes or data blocks with virtual block
addresses, whereas the B-tree of the DAT uses actual block addresses.

Signed-off-by: Koji Sato <sato.koji@lab.ntt.co.jp>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 2393 insertions, 0 deletions

diff --git a/fs/nilfs2/btree.c b/fs/nilfs2/btree.c
new file mode 100644
index 000000000000..893f0190a61f
--- /dev/null
+++ b/fs/nilfs2/btree.c
@@ -0,0 +1,2276 @@
+/*
+ * 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"
+
+/**
+ * struct nilfs_btree_path - A path on which B-tree operations are executed
+ * @bp_bh: buffer head of node block
+ * @bp_sib_bh: buffer head of sibling node block
+ * @bp_index: index of child node
+ * @bp_oldreq: ptr end request for old ptr
+ * @bp_newreq: ptr alloc request for new ptr
+ * @bp_op: rebalance operation
+ */
+struct nilfs_btree_path {
+        struct buffer_head *bp_bh;
+        struct buffer_head *bp_sib_bh;
+        int bp_index;
+        union nilfs_bmap_ptr_req bp_oldreq;
+        union nilfs_bmap_ptr_req bp_newreq;
+        struct nilfs_btnode_chkey_ctxt bp_ctxt;
+        void (*bp_op)(struct nilfs_btree *, struct nilfs_btree_path *,
+                      int, __u64 *, __u64 *);
+};
+
+/*
+ * B-tree path operations
+ */
+
+static struct kmem_cache *nilfs_btree_path_cache;
+
+int __init nilfs_btree_path_cache_init(void)
+{
+        nilfs_btree_path_cache =
+                kmem_cache_create("nilfs2_btree_path_cache",
+                                  sizeof(struct nilfs_btree_path) *
+                                  NILFS_BTREE_LEVEL_MAX, 0, 0, NULL);
+        return (nilfs_btree_path_cache != NULL) ? 0 : -ENOMEM;
+}
+
+void nilfs_btree_path_cache_destroy(void)
+{
+        kmem_cache_destroy(nilfs_btree_path_cache);
+}
+
+static inline struct nilfs_btree_path *
+nilfs_btree_alloc_path(const struct nilfs_btree *btree)
+{
+        return (struct nilfs_btree_path *)
+                kmem_cache_alloc(nilfs_btree_path_cache, GFP_NOFS);
+}
+
+static inline void nilfs_btree_free_path(const struct nilfs_btree *btree,
+                                         struct nilfs_btree_path *path)
+{
+        kmem_cache_free(nilfs_btree_path_cache, path);
+}
+
+static void nilfs_btree_init_path(const struct nilfs_btree *btree,
+                                  struct nilfs_btree_path *path)
+{
+        int level;
+
+        for (level = NILFS_BTREE_LEVEL_DATA;
+             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;
+        }
+}
+
+static void nilfs_btree_clear_path(const struct nilfs_btree *btree,
+                                   struct nilfs_btree_path *path)
+{
+        int level;
+
+        for (level = NILFS_BTREE_LEVEL_DATA;
+             level < NILFS_BTREE_LEVEL_MAX;
+             level++) {
+                if (path[level].bp_bh != NULL) {
+                        nilfs_bmap_put_block(&btree->bt_bmap,
+                                             path[level].bp_bh);
+                        path[level].bp_bh = NULL;
+                }
+                /* sib_bh is released or deleted by prepare or commit
+                 * operations. */
+                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;
+        }
+}
+
+
+/*
+ * B-tree node operations
+ */
+
+static inline int
+nilfs_btree_node_get_flags(const struct nilfs_btree *btree,
+                           const struct nilfs_btree_node *node)
+{
+        return node->bn_flags;
+}
+
+static inline void
+nilfs_btree_node_set_flags(struct nilfs_btree *btree,
+                           struct nilfs_btree_node *node,
+                           int flags)
+{
+        node->bn_flags = flags;
+}
+
+static inline int nilfs_btree_node_root(const struct nilfs_btree *btree,
+                                        const struct nilfs_btree_node *node)
+{
+        return nilfs_btree_node_get_flags(btree, node) & NILFS_BTREE_NODE_ROOT;
+}
+
+static inline int
+nilfs_btree_node_get_level(const struct nilfs_btree *btree,
+                           const struct nilfs_btree_node *node)
+{
+        return node->bn_level;
+}
+
+static inline void
+nilfs_btree_node_set_level(struct nilfs_btree *btree,
+                           struct nilfs_btree_node *node,
+                           int level)
+{
+        node->bn_level = level;
+}
+
+static inline int
+nilfs_btree_node_get_nchildren(const struct nilfs_btree *btree,
+                               const struct nilfs_btree_node *node)
+{
+        return le16_to_cpu(node->bn_nchildren);
+}
+
+static inline void
+nilfs_btree_node_set_nchildren(struct nilfs_btree *btree,
+                               struct nilfs_btree_node *node,
+                               int nchildren)
+{
+        node->bn_nchildren = cpu_to_le16(nchildren);
+}
+
+static inline int
+nilfs_btree_node_size(const struct nilfs_btree *btree)
+{
+        return 1 << btree->bt_bmap.b_inode->i_blkbits;
+}
+
+static inline int
+nilfs_btree_node_nchildren_min(const struct nilfs_btree *btree,
+                               const struct nilfs_btree_node *node)
+{
+        return nilfs_btree_node_root(btree, node) ?
+                NILFS_BTREE_ROOT_NCHILDREN_MIN :
+                NILFS_BTREE_NODE_NCHILDREN_MIN(nilfs_btree_node_size(btree));
+}
+
+static inline int
+nilfs_btree_node_nchildren_max(const struct nilfs_btree *btree,
+                               const struct nilfs_btree_node *node)
+{
+        return nilfs_btree_node_root(btree, node) ?
+                NILFS_BTREE_ROOT_NCHILDREN_MAX :
+                NILFS_BTREE_NODE_NCHILDREN_MAX(nilfs_btree_node_size(btree));
+}
+
+static inline __le64 *
+nilfs_btree_node_dkeys(const struct nilfs_btree *btree,
+                       const struct nilfs_btree_node *node)
+{
+        return (__le64 *)((char *)(node + 1) +
+                          (nilfs_btree_node_root(btree, node) ?
+                           0 : NILFS_BTREE_NODE_EXTRA_PAD_SIZE));
+}
+
+static inline __le64 *
+nilfs_btree_node_dptrs(const struct nilfs_btree *btree,
+                       const struct nilfs_btree_node *node)
+{
+        return (__le64 *)(nilfs_btree_node_dkeys(btree, node) +
+                          nilfs_btree_node_nchildren_max(btree, node));
+}
+
+static inline __u64
+nilfs_btree_node_get_key(const struct nilfs_btree *btree,
+                         const struct nilfs_btree_node *node, int index)
+{
+        return nilfs_bmap_dkey_to_key(*(nilfs_btree_node_dkeys(btree, node) +
+                                        index));
+}
+
+static inline void
+nilfs_btree_node_set_key(struct nilfs_btree *btree,
+                         struct nilfs_btree_node *node, int index, __u64 key)
+{
+        *(nilfs_btree_node_dkeys(btree, node) + index) =
+                nilfs_bmap_key_to_dkey(key);
+}
+
+static inline __u64
+nilfs_btree_node_get_ptr(const struct nilfs_btree *btree,
+                         const struct nilfs_btree_node *node,
+                         int index)
+{
+        return nilfs_bmap_dptr_to_ptr(*(nilfs_btree_node_dptrs(btree, node) +
+                                        index));
+}
+
+static inline void
+nilfs_btree_node_set_ptr(struct nilfs_btree *btree,
+                         struct nilfs_btree_node *node,
+                         int index,
+                         __u64 ptr)
+{
+        *(nilfs_btree_node_dptrs(btree, node) + index) =
+                nilfs_bmap_ptr_to_dptr(ptr);
+}
+
+static void nilfs_btree_node_init(struct nilfs_btree *btree,
+                                  struct nilfs_btree_node *node,
+                                  int flags, int level, int nchildren,
+                                  const __u64 *keys, const __u64 *ptrs)
+{
+        __le64 *dkeys;
+        __le64 *dptrs;
+        int i;
+
+        nilfs_btree_node_set_flags(btree, node, flags);
+        nilfs_btree_node_set_level(btree, node, level);
+        nilfs_btree_node_set_nchildren(btree, node, nchildren);
+
+        dkeys = nilfs_btree_node_dkeys(btree, node);
+        dptrs = nilfs_btree_node_dptrs(btree, node);
+        for (i = 0; i < nchildren; i++) {
+                dkeys[i] = nilfs_bmap_key_to_dkey(keys[i]);
+                dptrs[i] = nilfs_bmap_ptr_to_dptr(ptrs[i]);
+        }
+}
+
+/* Assume the buffer heads corresponding to left and right are locked. */
+static void nilfs_btree_node_move_left(struct nilfs_btree *btree,
+                                       struct nilfs_btree_node *left,
+                                       struct nilfs_btree_node *right,
+                                       int n)
+{
+        __le64 *ldkeys, *rdkeys;
+        __le64 *ldptrs, *rdptrs;
+        int lnchildren, rnchildren;
+
+        ldkeys = nilfs_btree_node_dkeys(btree, left);
+        ldptrs = nilfs_btree_node_dptrs(btree, left);
+        lnchildren = nilfs_btree_node_get_nchildren(btree, left);
+
+        rdkeys = nilfs_btree_node_dkeys(btree, right);
+        rdptrs = nilfs_btree_node_dptrs(btree, right);
+        rnchildren = nilfs_btree_node_get_nchildren(btree, 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(btree, left, lnchildren);
+        nilfs_btree_node_set_nchildren(btree, right, rnchildren);
+}
+
+/* Assume that the buffer heads corresponding to left and right are locked. */
+static void nilfs_btree_node_move_right(struct nilfs_btree *btree,
+                                        struct nilfs_btree_node *left,
+                                        struct nilfs_btree_node *right,
+                                        int n)
+{
+        __le64 *ldkeys, *rdkeys;
+        __le64 *ldptrs, *rdptrs;
+        int lnchildren, rnchildren;
+
+        ldkeys = nilfs_btree_node_dkeys(btree, left);
+        ldptrs = nilfs_btree_node_dptrs(btree, left);
+        lnchildren = nilfs_btree_node_get_nchildren(btree, left);
+
+        rdkeys = nilfs_btree_node_dkeys(btree, right);
+        rdptrs = nilfs_btree_node_dptrs(btree, right);
+        rnchildren = nilfs_btree_node_get_nchildren(btree, 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(btree, left, lnchildren);
+        nilfs_btree_node_set_nchildren(btree, right, rnchildren);
+}
+
+/* Assume that the buffer head corresponding to node is locked. */
+static void nilfs_btree_node_insert(struct nilfs_btree *btree,
+                                    struct nilfs_btree_node *node,
+                                    __u64 key, __u64 ptr, int index)
+{
+        __le64 *dkeys;
+        __le64 *dptrs;
+        int nchildren;
+
+        dkeys = nilfs_btree_node_dkeys(btree, node);
+        dptrs = nilfs_btree_node_dptrs(btree, node);
+        nchildren = nilfs_btree_node_get_nchildren(btree, 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] = nilfs_bmap_key_to_dkey(key);
+        dptrs[index] = nilfs_bmap_ptr_to_dptr(ptr);
+        nchildren++;
+        nilfs_btree_node_set_nchildren(btree, node, nchildren);
+}
+
+/* Assume that the buffer head corresponding to node is locked. */
+static void nilfs_btree_node_delete(struct nilfs_btree *btree,
+                                    struct nilfs_btree_node *node,
+                                    __u64 *keyp, __u64 *ptrp, int index)
+{
+        __u64 key;
+        __u64 ptr;
+        __le64 *dkeys;
+        __le64 *dptrs;
+        int nchildren;
+
+        dkeys = nilfs_btree_node_dkeys(btree, node);
+        dptrs = nilfs_btree_node_dptrs(btree, node);
+        key = nilfs_bmap_dkey_to_key(dkeys[index]);
+        ptr = nilfs_bmap_dptr_to_ptr(dptrs[index]);
+        nchildren = nilfs_btree_node_get_nchildren(btree, 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(btree, node, nchildren);
+}
+
+static int nilfs_btree_node_lookup(const struct nilfs_btree *btree,
+                                   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(btree, node) - 1;
+        index = 0;
+        s = 0;
+        while (low <= high) {
+                index = (low + high) / 2;
+                nkey = nilfs_btree_node_get_key(btree, 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(btree, node) >
+            NILFS_BTREE_LEVEL_NODE_MIN) {
+                if ((s > 0) && (index > 0))
+                        index--;
+        } else if (s < 0)
+                index++;
+
+ out:
+        BUG_ON(indexp == NULL);
+        *indexp = index;
+
+        return s == 0;
+}
+
+static inline struct nilfs_btree_node *
+nilfs_btree_get_root(const struct nilfs_btree *btree)
+{
+        return (struct nilfs_btree_node *)btree->bt_bmap.b_u.u_data;
+}
+
+static inline struct nilfs_btree_node *
+nilfs_btree_get_nonroot_node(const struct nilfs_btree *btree,
+                             const struct nilfs_btree_path *path,
+                             int level)
+{
+        return (struct nilfs_btree_node *)path[level].bp_bh->b_data;
+}
+
+static inline struct nilfs_btree_node *
+nilfs_btree_get_sib_node(const struct nilfs_btree *btree,
+                         const struct nilfs_btree_path *path,
+                         int level)
+{
+        return (struct nilfs_btree_node *)path[level].bp_sib_bh->b_data;
+}
+
+static inline int nilfs_btree_height(const struct nilfs_btree *btree)
+{
+        return nilfs_btree_node_get_level(btree, nilfs_btree_get_root(btree))
+                + 1;
+}
+
+static inline struct nilfs_btree_node *
+nilfs_btree_get_node(const struct nilfs_btree *btree,
+                     const struct nilfs_btree_path *path,
+                     int level)
+{
+        return (level == nilfs_btree_height(btree) - 1) ?
+                nilfs_btree_get_root(btree) :
+                nilfs_btree_get_nonroot_node(btree, path, level);
+}
+
+static int nilfs_btree_do_lookup(const struct nilfs_btree *btree,
+                                 struct nilfs_btree_path *path,
+                                 __u64 key, __u64 *ptrp, int minlevel)
+{
+        struct nilfs_btree_node *node;
+        __u64 ptr;
+        int level, index, found, ret;
+
+        BUG_ON(minlevel <= NILFS_BTREE_LEVEL_DATA);
+
+        node = nilfs_btree_get_root(btree);
+        level = nilfs_btree_node_get_level(btree, node);
+        if ((level < minlevel) ||
+            (nilfs_btree_node_get_nchildren(btree, node) <= 0))
+                return -ENOENT;
+
+        found = nilfs_btree_node_lookup(btree, node, key, &index);
+        ptr = nilfs_btree_node_get_ptr(btree, node, index);
+        path[level].bp_bh = NULL;
+        path[level].bp_index = index;
+
+        for (level--; level >= minlevel; level--) {
+                ret = nilfs_bmap_get_block(&btree->bt_bmap, ptr,
+                                           &path[level].bp_bh);
+                if (ret < 0)
+                        return ret;
+                node = nilfs_btree_get_nonroot_node(btree, path, level);
+                BUG_ON(level != nilfs_btree_node_get_level(btree, node));
+                if (!found)
+                        found = nilfs_btree_node_lookup(btree, node, key,
+                                                        &index);
+                else
+                        index = 0;
+                if (index < nilfs_btree_node_nchildren_max(btree, node))
+                        ptr = nilfs_btree_node_get_ptr(btree, node, index);
+                else {
+                        BUG_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_btree *btree,
+                                      struct nilfs_btree_path *path,
+                                      __u64 *keyp, __u64 *ptrp)
+{
+        struct nilfs_btree_node *node;
+        __u64 ptr;
+        int index, level, ret;
+
+        node = nilfs_btree_get_root(btree);
+        index = nilfs_btree_node_get_nchildren(btree, node) - 1;
+        if (index < 0)
+                return -ENOENT;
+        level = nilfs_btree_node_get_level(btree, node);
+        ptr = nilfs_btree_node_get_ptr(btree, node, index);
+        path[level].bp_bh = NULL;
+        path[level].bp_index = index;
+
+        for (level--; level > 0; level--) {
+                ret = nilfs_bmap_get_block(&btree->bt_bmap, ptr,
+                                           &path[level].bp_bh);
+                if (ret < 0)
+                        return ret;
+                node = nilfs_btree_get_nonroot_node(btree, path, level);
+                BUG_ON(level != nilfs_btree_node_get_level(btree, node));
+                index = nilfs_btree_node_get_nchildren(btree, node) - 1;
+                ptr = nilfs_btree_node_get_ptr(btree, node, index);
+                path[level].bp_index = index;
+        }
+
+        if (keyp != NULL)
+                *keyp = nilfs_btree_node_get_key(btree, node, index);
+        if (ptrp != NULL)
+                *ptrp = ptr;
+
+        return 0;
+}
+
+static int nilfs_btree_lookup(const struct nilfs_bmap *bmap,
+                              __u64 key, int level, __u64 *ptrp)
+{
+        struct nilfs_btree *btree;
+        struct nilfs_btree_path *path;
+        __u64 ptr;
+        int ret;
+
+        btree = (struct nilfs_btree *)bmap;
+        path = nilfs_btree_alloc_path(btree);
+        if (path == NULL)
+                return -ENOMEM;
+        nilfs_btree_init_path(btree, path);
+
+        ret = nilfs_btree_do_lookup(btree, path, key, &ptr, level);
+
+        if (ptrp != NULL)
+                *ptrp = ptr;
+
+        nilfs_btree_clear_path(btree, path);
+        nilfs_btree_free_path(btree, path);
+
+        return ret;
+}
+
+static void nilfs_btree_promote_key(struct nilfs_btree *btree,
+                                    struct nilfs_btree_path *path,
+                                    int level, __u64 key)
+{
+        if (level < nilfs_btree_height(btree) - 1) {
+                do {
+                        lock_buffer(path[level].bp_bh);
+                        nilfs_btree_node_set_key(
+                                btree,
+                                nilfs_btree_get_nonroot_node(
+                                        btree, path, level),
+                                path[level].bp_index, key);
+                        if (!buffer_dirty(path[level].bp_bh))
+                                nilfs_btnode_mark_dirty(path[level].bp_bh);
+                        unlock_buffer(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(btree,
+                                         nilfs_btree_get_root(btree),
+                                         path[level].bp_index, key);
+        }
+}
+
+static void nilfs_btree_do_insert(struct nilfs_btree *btree,
+                                  struct nilfs_btree_path *path,
+                                  int level, __u64 *keyp, __u64 *ptrp)
+{
+        struct nilfs_btree_node *node;
+
+        if (level < nilfs_btree_height(btree) - 1) {
+                lock_buffer(path[level].bp_bh);
+                node = nilfs_btree_get_nonroot_node(btree, path, level);
+                nilfs_btree_node_insert(btree, node, *keyp, *ptrp,
+                                        path[level].bp_index);
+                if (!buffer_dirty(path[level].bp_bh))
+                        nilfs_btnode_mark_dirty(path[level].bp_bh);
+                unlock_buffer(path[level].bp_bh);
+
+                if (path[level].bp_index == 0)
+                        nilfs_btree_promote_key(btree, path, level + 1,
+                                                nilfs_btree_node_get_key(
+                                                        btree, node, 0));
+        } else {
+                node = nilfs_btree_get_root(btree);
+                nilfs_btree_node_insert(btree, node, *keyp, *ptrp,
+                                        path[level].bp_index);
+        }
+}
+
+static void nilfs_btree_carry_left(struct nilfs_btree *btree,
+                                   struct nilfs_btree_path *path,
+                                   int level, __u64 *keyp, __u64 *ptrp)
+{
+        struct nilfs_btree_node *node, *left;
+        int nchildren, lnchildren, n, move;
+
+        lock_buffer(path[level].bp_bh);
+        lock_buffer(path[level].bp_sib_bh);
+
+        node = nilfs_btree_get_nonroot_node(btree, path, level);
+        left = nilfs_btree_get_sib_node(btree, path, level);
+        nchildren = nilfs_btree_node_get_nchildren(btree, node);
+        lnchildren = nilfs_btree_node_get_nchildren(btree, left);
+        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(btree, left, node, n);
+
+        if (!buffer_dirty(path[level].bp_bh))
+                nilfs_btnode_mark_dirty(path[level].bp_bh);
+        if (!buffer_dirty(path[level].bp_sib_bh))
+                nilfs_btnode_mark_dirty(path[level].bp_sib_bh);
+
+        unlock_buffer(path[level].bp_bh);
+        unlock_buffer(path[level].bp_sib_bh);
+
+        nilfs_btree_promote_key(btree, path, level + 1,
+                                nilfs_btree_node_get_key(btree, node, 0));
+
+        if (move) {
+                nilfs_bmap_put_block(&btree->bt_bmap, 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 {
+                nilfs_bmap_put_block(&btree->bt_bmap, 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_btree *btree,
+                                    struct nilfs_btree_path *path,
+                                    int level, __u64 *keyp, __u64 *ptrp)
+{
+        struct nilfs_btree_node *node, *right;
+        int nchildren, rnchildren, n, move;
+
+        lock_buffer(path[level].bp_bh);
+        lock_buffer(path[level].bp_sib_bh);
+
+        node = nilfs_btree_get_nonroot_node(btree, path, level);
+        right = nilfs_btree_get_sib_node(btree, path, level);
+        nchildren = nilfs_btree_node_get_nchildren(btree, node);
+        rnchildren = nilfs_btree_node_get_nchildren(btree, right);
+        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(btree, node, right, n);
+
+        if (!buffer_dirty(path[level].bp_bh))
+                nilfs_btnode_mark_dirty(path[level].bp_bh);
+        if (!buffer_dirty(path[level].bp_sib_bh))
+                nilfs_btnode_mark_dirty(path[level].bp_sib_bh);
+
+        unlock_buffer(path[level].bp_bh);
+        unlock_buffer(path[level].bp_sib_bh);
+
+        path[level + 1].bp_index++;
+        nilfs_btree_promote_key(btree, path, level + 1,
+                                nilfs_btree_node_get_key(btree, right, 0));
+        path[level + 1].bp_index--;
+
+        if (move) {
+                nilfs_bmap_put_block(&btree->bt_bmap, 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(btree, node);
+                path[level + 1].bp_index++;
+        } else {
+                nilfs_bmap_put_block(&btree->bt_bmap, 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_btree *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;
+
+        lock_buffer(path[level].bp_bh);
+        lock_buffer(path[level].bp_sib_bh);
+
+        node = nilfs_btree_get_nonroot_node(btree, path, level);
+        right = nilfs_btree_get_sib_node(btree, path, level);
+        nchildren = nilfs_btree_node_get_nchildren(btree, node);
+        move = 0;
+
+        n = (nchildren + 1) / 2;
+        if (n > nchildren - path[level].bp_index) {
+                n--;
+                move = 1;
+        }
+
+        nilfs_btree_node_move_right(btree, node, right, n);
+
+        if (!buffer_dirty(path[level].bp_bh))
+                nilfs_btnode_mark_dirty(path[level].bp_bh);
+        if (!buffer_dirty(path[level].bp_sib_bh))
+                nilfs_btnode_mark_dirty(path[level].bp_sib_bh);
+
+        unlock_buffer(path[level].bp_bh);
+        unlock_buffer(path[level].bp_sib_bh);
+
+        newkey = nilfs_btree_node_get_key(btree, right, 0);
+        newptr = path[level].bp_newreq.bpr_ptr;
+
+        if (move) {
+                path[level].bp_index -=
+                        nilfs_btree_node_get_nchildren(btree, node);
+                nilfs_btree_node_insert(btree, right, *keyp, *ptrp,
+                                        path[level].bp_index);
+
+                *keyp = nilfs_btree_node_get_key(btree, right, 0);
+                *ptrp = path[level].bp_newreq.bpr_ptr;
+
+                nilfs_bmap_put_block(&btree->bt_bmap, 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(btree, right, 0);
+                *ptrp = path[level].bp_newreq.bpr_ptr;
+
+                nilfs_bmap_put_block(&btree->bt_bmap, path[level].bp_sib_bh);
+                path[level].bp_sib_bh = NULL;
+        }
+
+        path[level + 1].bp_index++;
+}
+
+static void nilfs_btree_grow(struct nilfs_btree *btree,
+                             struct nilfs_btree_path *path,
+                             int level, __u64 *keyp, __u64 *ptrp)
+{
+        struct nilfs_btree_node *root, *child;
+        int n;
+
+        lock_buffer(path[level].bp_sib_bh);
+
+        root = nilfs_btree_get_root(btree);
+        child = nilfs_btree_get_sib_node(btree, path, level);
+
+        n = nilfs_btree_node_get_nchildren(btree, root);
+
+        nilfs_btree_node_move_right(btree, root, child, n);
+        nilfs_btree_node_set_level(btree, root, level + 1);
+
+        if (!buffer_dirty(path[level].bp_sib_bh))
+                nilfs_btnode_mark_dirty(path[level].bp_sib_bh);
+
+        unlock_buffer(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(btree, child, 0);
+        *ptrp = path[level].bp_newreq.bpr_ptr;
+}
+
+static __u64 nilfs_btree_find_near(const struct nilfs_btree *btree,
+                                   const struct nilfs_btree_path *path)
+{
+        struct nilfs_btree_node *node;
+        int level;
+
+        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);
+                return nilfs_btree_node_get_ptr(btree, node,
+                                                path[level].bp_index - 1);
+        }
+
+        /* parent */
+        level = NILFS_BTREE_LEVEL_NODE_MIN + 1;
+        if (level <= nilfs_btree_height(btree) - 1) {
+                node = nilfs_btree_get_node(btree, path, level);
+                return nilfs_btree_node_get_ptr(btree, node,
+                                                path[level].bp_index);
+        }
+
+        return NILFS_BMAP_INVALID_PTR;
+}
+
+static __u64 nilfs_btree_find_target_v(const struct nilfs_btree *btree,
+                                       const struct nilfs_btree_path *path,
+                                       __u64 key)
+{
+        __u64 ptr;
+
+        ptr = nilfs_bmap_find_target_seq(&btree->bt_bmap, 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->bt_bmap);
+}
+
+static void nilfs_btree_set_target_v(struct nilfs_btree *btree, __u64 key,
+                                     __u64 ptr)
+{
+        btree->bt_bmap.b_last_allocated_key = key;
+        btree->bt_bmap.b_last_allocated_ptr = ptr;
+}
+
+static int nilfs_btree_prepare_insert(struct nilfs_btree *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, ret;
+
+        stats->bs_nblocks = 0;
+        level = NILFS_BTREE_LEVEL_DATA;
+
+        /* allocate a new ptr for data block */
+        if (btree->bt_ops->btop_find_target != NULL)
+                path[level].bp_newreq.bpr_ptr =
+                        (*btree->bt_ops->btop_find_target)(btree, path, key);
+
+        ret = (*btree->bt_bmap.b_pops->bpop_prepare_alloc_ptr)(
+                &btree->bt_bmap, &path[level].bp_newreq);
+        if (ret < 0)
+                goto err_out_data;
+
+        for (level = NILFS_BTREE_LEVEL_NODE_MIN;
+             level < nilfs_btree_height(btree) - 1;
+             level++) {
+                node = nilfs_btree_get_nonroot_node(btree, path, level);
+                if (nilfs_btree_node_get_nchildren(btree, node) <
+                    nilfs_btree_node_nchildren_max(btree, node)) {
+                        path[level].bp_op = nilfs_btree_do_insert;
+                        stats->bs_nblocks++;
+                        goto out;
+                }
+
+                parent = nilfs_btree_get_node(btree, path, level + 1);
+                pindex = path[level + 1].bp_index;
+
+                /* left sibling */
+                if (pindex > 0) {
+                        sibptr = nilfs_btree_node_get_ptr(btree, parent,
+                                                          pindex - 1);
+                        ret = nilfs_bmap_get_block(&btree->bt_bmap, sibptr,
+                                                   &bh);
+                        if (ret < 0)
+                                goto err_out_child_node;
+                        sib = (struct nilfs_btree_node *)bh->b_data;
+                        if (nilfs_btree_node_get_nchildren(btree, sib) <
+                            nilfs_btree_node_nchildren_max(btree, sib)) {
+                                path[level].bp_sib_bh = bh;
+                                path[level].bp_op = nilfs_btree_carry_left;
+                                stats->bs_nblocks++;
+                                goto out;
+                        } else
+                                nilfs_bmap_put_block(&btree->bt_bmap, bh);
+                }
+
+                /* right sibling */
+                if (pindex <
+                    nilfs_btree_node_get_nchildren(btree, parent) - 1) {
+                        sibptr = nilfs_btree_node_get_ptr(btree, parent,
+                                                          pindex + 1);
+                        ret = nilfs_bmap_get_block(&btree->bt_bmap, sibptr,
+                                                   &bh);
+                        if (ret < 0)
+                                goto err_out_child_node;
+                        sib = (struct nilfs_btree_node *)bh->b_data;
+                        if (nilfs_btree_node_get_nchildren(btree, sib) <
+                            nilfs_btree_node_nchildren_max(btree, sib)) {
+                                path[level].bp_sib_bh = bh;
+                                path[level].bp_op = nilfs_btree_carry_right;
+                                stats->bs_nblocks++;
+                                goto out;
+                        } else
+                                nilfs_bmap_put_block(&btree->bt_bmap, bh);
+                }
+
+                /* split */
+                path[level].bp_newreq.bpr_ptr =
+                        path[level - 1].bp_newreq.bpr_ptr + 1;
+                ret = (*btree->bt_bmap.b_pops->bpop_prepare_alloc_ptr)(
+                        &btree->bt_bmap, &path[level].bp_newreq);
+                if (ret < 0)
+                        goto err_out_child_node;
+                ret = nilfs_bmap_get_new_block(&btree->bt_bmap,
+                                               path[level].bp_newreq.bpr_ptr,
+                                               &bh);
+                if (ret < 0)
+                        goto err_out_curr_node;
+
+                stats->bs_nblocks++;
+
+                lock_buffer(bh);
+                nilfs_btree_node_init(btree,
+                                      (struct nilfs_btree_node *)bh->b_data,
+                                      0, level, 0, NULL, NULL);
+                unlock_buffer(bh);
+                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(btree, node) <
+            nilfs_btree_node_nchildren_max(btree, node)) {
+                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 = (*btree->bt_bmap.b_pops->bpop_prepare_alloc_ptr)(
+                &btree->bt_bmap, &path[level].bp_newreq);
+        if (ret < 0)
+                goto err_out_child_node;
+        ret = nilfs_bmap_get_new_block(&btree->bt_bmap,
+                                       path[level].bp_newreq.bpr_ptr, &bh);
+        if (ret < 0)
+                goto err_out_curr_node;
+
+        lock_buffer(bh);
+        nilfs_btree_node_init(btree, (struct nilfs_btree_node *)bh->b_data,
+                              0, level, 0, NULL, NULL);
+        unlock_buffer(bh);
+        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:
+        (*btree->bt_bmap.b_pops->bpop_abort_alloc_ptr)(&btree->bt_bmap,
+                                                       &path[level].bp_newreq);
+ err_out_child_node:
+        for (level--; level > NILFS_BTREE_LEVEL_DATA; level--) {
+                nilfs_bmap_delete_block(&btree->bt_bmap, path[level].bp_sib_bh);
+                (*btree->bt_bmap.b_pops->bpop_abort_alloc_ptr)(
+                        &btree->bt_bmap, &path[level].bp_newreq);
+
+        }
+
+        (*btree->bt_bmap.b_pops->bpop_abort_alloc_ptr)(&btree->bt_bmap,
+                                                       &path[level].bp_newreq);
+ err_out_data:
+        *levelp = level;
+        stats->bs_nblocks = 0;
+        return ret;
+}
+
+static void nilfs_btree_commit_insert(struct nilfs_btree *btree,
+                                      struct nilfs_btree_path *path,
+                                      int maxlevel, __u64 key, __u64 ptr)
+{
+        int level;
+
+        set_buffer_nilfs_volatile((struct buffer_head *)((unsigned long)ptr));
+        ptr = path[NILFS_BTREE_LEVEL_DATA].bp_newreq.bpr_ptr;
+        if (btree->bt_ops->btop_set_target != NULL)
+                (*btree->bt_ops->btop_set_target)(btree, key, ptr);
+
+        for (level = NILFS_BTREE_LEVEL_NODE_MIN; level <= maxlevel; level++) {
+                if (btree->bt_bmap.b_pops->bpop_commit_alloc_ptr != NULL) {
+                        (*btree->bt_bmap.b_pops->bpop_commit_alloc_ptr)(
+                                &btree->bt_bmap, &path[level - 1].bp_newreq);
+                }
+                (*path[level].bp_op)(btree, path, level, &key, &ptr);
+        }
+
+        if (!nilfs_bmap_dirty(&btree->bt_bmap))
+                nilfs_bmap_set_dirty(&btree->bt_bmap);
+}
+
+static int nilfs_btree_insert(struct nilfs_bmap *bmap, __u64 key, __u64 ptr)
+{
+        struct nilfs_btree *btree;
+        struct nilfs_btree_path *path;
+        struct nilfs_bmap_stats stats;
+        int level, ret;
+
+        btree = (struct nilfs_btree *)bmap;
+        path = nilfs_btree_alloc_path(btree);
+        if (path == NULL)
+                return -ENOMEM;
+        nilfs_btree_init_path(btree, path);
+
+        ret = nilfs_btree_do_lookup(btree, path, key, NULL,
+                                    NILFS_BTREE_LEVEL_NODE_MIN);
+        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_bmap_add_blocks(bmap, stats.bs_nblocks);
+
+ out:
+        nilfs_btree_clear_path(btree, path);
+        nilfs_btree_free_path(btree, path);
+        return ret;
+}
+
+static void nilfs_btree_do_delete(struct nilfs_btree *btree,
+                                  struct nilfs_btree_path *path,
+                                  int level, __u64 *keyp, __u64 *ptrp)
+{
+        struct nilfs_btree_node *node;
+
+        if (level < nilfs_btree_height(btree) - 1) {
+                lock_buffer(path[level].bp_bh);
+                node = nilfs_btree_get_nonroot_node(btree, path, level);
+                nilfs_btree_node_delete(btree, node, keyp, ptrp,
+                                        path[level].bp_index);
+                if (!buffer_dirty(path[level].bp_bh))
+                        nilfs_btnode_mark_dirty(path[level].bp_bh);
+                unlock_buffer(path[level].bp_bh);
+                if (path[level].bp_index == 0)
+                        nilfs_btree_promote_key(btree, path, level + 1,
+                                nilfs_btree_node_get_key(btree, node, 0));
+        } else {
+                node = nilfs_btree_get_root(btree);
+                nilfs_btree_node_delete(btree, node, keyp, ptrp,
+                                        path[level].bp_index);
+        }
+}
+
+static void nilfs_btree_borrow_left(struct nilfs_btree *btree,
+                                    struct nilfs_btree_path *path,
+                                    int level, __u64 *keyp, __u64 *ptrp)
+{
+        struct nilfs_btree_node *node, *left;
+        int nchildren, lnchildren, n;
+
+        nilfs_btree_do_delete(btree, path, level, keyp, ptrp);
+
+        lock_buffer(path[level].bp_bh);
+        lock_buffer(path[level].bp_sib_bh);
+
+        node = nilfs_btree_get_nonroot_node(btree, path, level);
+        left = nilfs_btree_get_sib_node(btree, path, level);
+        nchildren = nilfs_btree_node_get_nchildren(btree, node);
+        lnchildren = nilfs_btree_node_get_nchildren(btree, left);
+
+        n = (nchildren + lnchildren) / 2 - nchildren;
+
+        nilfs_btree_node_move_right(btree, left, node, n);
+
+        if (!buffer_dirty(path[level].bp_bh))
+                nilfs_btnode_mark_dirty(path[level].bp_bh);
+        if (!buffer_dirty(path[level].bp_sib_bh))
+                nilfs_btnode_mark_dirty(path[level].bp_sib_bh);
+
+        unlock_buffer(path[level].bp_bh);
+        unlock_buffer(path[level].bp_sib_bh);
+
+        nilfs_btree_promote_key(btree, path, level + 1,
+                                nilfs_btree_node_get_key(btree, node, 0));
+
+        nilfs_bmap_put_block(&btree->bt_bmap, path[level].bp_sib_bh);
+        path[level].bp_sib_bh = NULL;
+        path[level].bp_index += n;
+}
+
+static void nilfs_btree_borrow_right(struct nilfs_btree *btree,
+                                     struct nilfs_btree_path *path,
+                                     int level, __u64 *keyp, __u64 *ptrp)
+{
+        struct nilfs_btree_node *node, *right;
+        int nchildren, rnchildren, n;
+
+        nilfs_btree_do_delete(btree, path, level, keyp, ptrp);
+
+        lock_buffer(path[level].bp_bh);
+        lock_buffer(path[level].bp_sib_bh);
+
+        node = nilfs_btree_get_nonroot_node(btree, path, level);
+        right = nilfs_btree_get_sib_node(btree, path, level);
+        nchildren = nilfs_btree_node_get_nchildren(btree, node);
+        rnchildren = nilfs_btree_node_get_nchildren(btree, right);
+
+        n = (nchildren + rnchildren) / 2 - nchildren;
+
+        nilfs_btree_node_move_left(btree, node, right, n);
+
+        if (!buffer_dirty(path[level].bp_bh))
+                nilfs_btnode_mark_dirty(path[level].bp_bh);
+        if (!buffer_dirty(path[level].bp_sib_bh))
+                nilfs_btnode_mark_dirty(path[level].bp_sib_bh);
+
+        unlock_buffer(path[level].bp_bh);
+        unlock_buffer(path[level].bp_sib_bh);
+
+        path[level + 1].bp_index++;
+        nilfs_btree_promote_key(btree, path, level + 1,
+                                nilfs_btree_node_get_key(btree, right, 0));
+        path[level + 1].bp_index--;
+
+        nilfs_bmap_put_block(&btree->bt_bmap, path[level].bp_sib_bh);
+        path[level].bp_sib_bh = NULL;
+}
+
+static void nilfs_btree_concat_left(struct nilfs_btree *btree,
+                                    struct nilfs_btree_path *path,
+                                    int level, __u64 *keyp, __u64 *ptrp)
+{
+        struct nilfs_btree_node *node, *left;
+        int n;
+
+        nilfs_btree_do_delete(btree, path, level, keyp, ptrp);
+
+        lock_buffer(path[level].bp_bh);
+        lock_buffer(path[level].bp_sib_bh);
+
+        node = nilfs_btree_get_nonroot_node(btree, path, level);
+        left = nilfs_btree_get_sib_node(btree, path, level);
+
+        n = nilfs_btree_node_get_nchildren(btree, node);
+
+        nilfs_btree_node_move_left(btree, left, node, n);
+
+        if (!buffer_dirty(path[level].bp_sib_bh))
+                nilfs_btnode_mark_dirty(path[level].bp_sib_bh);
+
+        unlock_buffer(path[level].bp_bh);
+        unlock_buffer(path[level].bp_sib_bh);
+
+        nilfs_bmap_delete_block(&btree->bt_bmap, 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(btree, left);
+}
+
+static void nilfs_btree_concat_right(struct nilfs_btree *btree,
+                                     struct nilfs_btree_path *path,
+                                     int level, __u64 *keyp, __u64 *ptrp)
+{
+        struct nilfs_btree_node *node, *right;
+        int n;
+
+        nilfs_btree_do_delete(btree, path, level, keyp, ptrp);
+
+        lock_buffer(path[level].bp_bh);
+        lock_buffer(path[level].bp_sib_bh);
+
+        node = nilfs_btree_get_nonroot_node(btree, path, level);
+        right = nilfs_btree_get_sib_node(btree, path, level);
+
+        n = nilfs_btree_node_get_nchildren(btree, right);
+
+        nilfs_btree_node_move_left(btree, node, right, n);
+
+        if (!buffer_dirty(path[level].bp_bh))
+                nilfs_btnode_mark_dirty(path[level].bp_bh);
+
+        unlock_buffer(path[level].bp_bh);
+        unlock_buffer(path[level].bp_sib_bh);
+
+        nilfs_bmap_delete_block(&btree->bt_bmap, path[level].bp_sib_bh);
+        path[level].bp_sib_bh = NULL;
+        path[level + 1].bp_index++;
+}
+
+static void nilfs_btree_shrink(struct nilfs_btree *btree,
+                               struct nilfs_btree_path *path,
+                               int level, __u64 *keyp, __u64 *ptrp)
+{
+        struct nilfs_btree_node *root, *child;
+        int n;
+
+        nilfs_btree_do_delete(btree, path, level, keyp, ptrp);
+
+        lock_buffer(path[level].bp_bh);
+        root = nilfs_btree_get_root(btree);
+        child = nilfs_btree_get_nonroot_node(btree, path, level);
+
+        nilfs_btree_node_delete(btree, root, NULL, NULL, 0);
+        nilfs_btree_node_set_level(btree, root, level);
+        n = nilfs_btree_node_get_nchildren(btree, child);
+        nilfs_btree_node_move_left(btree, root, child, n);
+        unlock_buffer(path[level].bp_bh);
+
+        nilfs_bmap_delete_block(&btree->bt_bmap, path[level].bp_bh);
+        path[level].bp_bh = NULL;
+}
+
+
+static int nilfs_btree_prepare_delete(struct nilfs_btree *btree,
+                                      struct nilfs_btree_path *path,
+                                      int *levelp,
+                                      struct nilfs_bmap_stats *stats)
+{
+        struct buffer_head *bh;
+        struct nilfs_btree_node *node, *parent, *sib;
+        __u64 sibptr;
+        int pindex, level, ret;
+
+        ret = 0;
+        stats->bs_nblocks = 0;
+        for (level = NILFS_BTREE_LEVEL_NODE_MIN;
+             level < nilfs_btree_height(btree) - 1;
+             level++) {
+                node = nilfs_btree_get_nonroot_node(btree, path, level);
+                path[level].bp_oldreq.bpr_ptr =
+                        nilfs_btree_node_get_ptr(btree, node,
+                                                 path[level].bp_index);
+                if (btree->bt_bmap.b_pops->bpop_prepare_end_ptr != NULL) {
+                        ret = (*btree->bt_bmap.b_pops->bpop_prepare_end_ptr)(
+                                &btree->bt_bmap, &path[level].bp_oldreq);
+                        if (ret < 0)
+                                goto err_out_child_node;
+                }
+
+                if (nilfs_btree_node_get_nchildren(btree, node) >
+                    nilfs_btree_node_nchildren_min(btree, node)) {
+                        path[level].bp_op = nilfs_btree_do_delete;
+                        stats->bs_nblocks++;
+                        goto out;
+                }
+
+                parent = nilfs_btree_get_node(btree, path, level + 1);
+                pindex = path[level + 1].bp_index;
+
+                if (pindex > 0) {
+                        /* left sibling */
+                        sibptr = nilfs_btree_node_get_ptr(btree, parent,
+                                                          pindex - 1);
+                        ret = nilfs_bmap_get_block(&btree->bt_bmap, sibptr,
+                                                   &bh);
+                        if (ret < 0)
+                                goto err_out_curr_node;
+                        sib = (struct nilfs_btree_node *)bh->b_data;
+                        if (nilfs_btree_node_get_nchildren(btree, sib) >
+                            nilfs_btree_node_nchildren_min(btree, sib)) {
+                                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(btree, parent) - 1) {
+                        /* right sibling */
+                        sibptr = nilfs_btree_node_get_ptr(btree, parent,
+                                                          pindex + 1);
+                        ret = nilfs_bmap_get_block(&btree->bt_bmap, sibptr,
+                                                   &bh);
+                        if (ret < 0)
+                                goto err_out_curr_node;
+                        sib = (struct nilfs_btree_node *)bh->b_data;
+                        if (nilfs_btree_node_get_nchildren(btree, sib) >
+                            nilfs_btree_node_nchildren_min(btree, sib)) {
+                                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++;
+                                /* continue; */
+                        }
+                } else {
+                        /* no siblings */
+                        /* the only child of the root node */
+                        BUG_ON(level != nilfs_btree_height(btree) - 2);
+                        if (nilfs_btree_node_get_nchildren(btree, node) - 1 <=
+                            NILFS_BTREE_ROOT_NCHILDREN_MAX) {
+                                path[level].bp_op = nilfs_btree_shrink;
+                                stats->bs_nblocks += 2;
+                        } else {
+                                path[level].bp_op = nilfs_btree_do_delete;
+                                stats->bs_nblocks++;
+                        }
+
+                        goto out;
+
+                }
+        }
+
+        node = nilfs_btree_get_root(btree);
+        path[level].bp_oldreq.bpr_ptr =
+                nilfs_btree_node_get_ptr(btree, node, path[level].bp_index);
+        if (btree->bt_bmap.b_pops->bpop_prepare_end_ptr != NULL) {
+                ret = (*btree->bt_bmap.b_pops->bpop_prepare_end_ptr)(
+                        &btree->bt_bmap, &path[level].bp_oldreq);
+                if (ret < 0)
+                        goto err_out_child_node;
+        }
+        /* child of the root node is deleted */
+        path[level].bp_op = nilfs_btree_do_delete;
+        stats->bs_nblocks++;
+
+        /* success */
+ out:
+        *levelp = level;
+        return ret;
+
+        /* error */
+ err_out_curr_node:
+        if (btree->bt_bmap.b_pops->bpop_abort_end_ptr != NULL)
+                (*btree->bt_bmap.b_pops->bpop_abort_end_ptr)(
+                        &btree->bt_bmap, &path[level].bp_oldreq);
+ err_out_child_node:
+        for (level--; level >= NILFS_BTREE_LEVEL_NODE_MIN; level--) {
+                nilfs_bmap_put_block(&btree->bt_bmap, path[level].bp_sib_bh);
+                if (btree->bt_bmap.b_pops->bpop_abort_end_ptr != NULL)
+                        (*btree->bt_bmap.b_pops->bpop_abort_end_ptr)(
+                                &btree->bt_bmap, &path[level].bp_oldreq);
+        }
+        *levelp = level;
+        stats->bs_nblocks = 0;
+        return ret;
+}
+
+static void nilfs_btree_commit_delete(struct nilfs_btree *btree,
+                                      struct nilfs_btree_path *path,
+                                      int maxlevel)
+{
+        int level;
+
+        for (level = NILFS_BTREE_LEVEL_NODE_MIN; level <= maxlevel; level++) {
+                if (btree->bt_bmap.b_pops->bpop_commit_end_ptr != NULL)
+                        (*btree->bt_bmap.b_pops->bpop_commit_end_ptr)(
+                                &btree->bt_bmap, &path[level].bp_oldreq);
+                (*path[level].bp_op)(btree, path, level, NULL, NULL);
+        }
+
+        if (!nilfs_bmap_dirty(&btree->bt_bmap))
+                nilfs_bmap_set_dirty(&btree->bt_bmap);
+}
+
+static int nilfs_btree_delete(struct nilfs_bmap *bmap, __u64 key)
+
+{
+        struct nilfs_btree *btree;
+        struct nilfs_btree_path *path;
+        struct nilfs_bmap_stats stats;
+        int level, ret;
+
+        btree = (struct nilfs_btree *)bmap;
+        path = nilfs_btree_alloc_path(btree);
+        if (path == NULL)
+                return -ENOMEM;
+        nilfs_btree_init_path(btree, path);
+        ret = nilfs_btree_do_lookup(btree, path, key, NULL,
+                                    NILFS_BTREE_LEVEL_NODE_MIN);
+        if (ret < 0)
+                goto out;
+
+        ret = nilfs_btree_prepare_delete(btree, path, &level, &stats);
+        if (ret < 0)
+                goto out;
+        nilfs_btree_commit_delete(btree, path, level);
+        nilfs_bmap_sub_blocks(bmap, stats.bs_nblocks);
+
+out:
+        nilfs_btree_clear_path(btree, path);
+        nilfs_btree_free_path(btree, path);
+        return ret;
+}
+
+static int nilfs_btree_last_key(const struct nilfs_bmap *bmap, __u64 *keyp)
+{
+        struct nilfs_btree *btree;
+        struct nilfs_btree_path *path;
+        int ret;
+
+        btree = (struct nilfs_btree *)bmap;
+        path = nilfs_btree_alloc_path(btree);
+        if (path == NULL)
+                return -ENOMEM;
+        nilfs_btree_init_path(btree, path);
+
+        ret = nilfs_btree_do_lookup_last(btree, path, keyp, NULL);
+
+        nilfs_btree_clear_path(btree, path);
+        nilfs_btree_free_path(btree, path);
+
+        return ret;
+}
+
+static int nilfs_btree_check_delete(struct nilfs_bmap *bmap, __u64 key)
+{
+        struct buffer_head *bh;
+        struct nilfs_btree *btree;
+        struct nilfs_btree_node *root, *node;
+        __u64 maxkey, nextmaxkey;
+        __u64 ptr;
+        int nchildren, ret;
+
+        btree = (struct nilfs_btree *)bmap;
+        root = nilfs_btree_get_root(btree);
+        switch (nilfs_btree_height(btree)) {
+        case 2:
+                bh = NULL;
+                node = root;
+                break;
+        case 3:
+                nchildren = nilfs_btree_node_get_nchildren(btree, root);
+                if (nchildren > 1)
+                        return 0;
+                ptr = nilfs_btree_node_get_ptr(btree, root, nchildren - 1);
+                ret = nilfs_bmap_get_block(bmap, ptr, &bh);
+                if (ret < 0)
+                        return ret;
+                node = (struct nilfs_btree_node *)bh->b_data;
+                break;
+        default:
+                return 0;
+        }
+
+        nchildren = nilfs_btree_node_get_nchildren(btree, node);
+        maxkey = nilfs_btree_node_get_key(btree, node, nchildren - 1);
+        nextmaxkey = (nchildren > 1) ?
+                nilfs_btree_node_get_key(btree, node, nchildren - 2) : 0;
+        if (bh != NULL)
+                nilfs_bmap_put_block(bmap, bh);
+
+        return (maxkey == key) && (nextmaxkey < bmap->b_low);
+}
+
+static int nilfs_btree_gather_data(struct nilfs_bmap *bmap,
+                                   __u64 *keys, __u64 *ptrs, int nitems)
+{
+        struct buffer_head *bh;
+        struct nilfs_btree *btree;
+        struct nilfs_btree_node *node, *root;
+        __le64 *dkeys;
+        __le64 *dptrs;
+        __u64 ptr;
+        int nchildren, i, ret;
+
+        btree = (struct nilfs_btree *)bmap;
+        root = nilfs_btree_get_root(btree);
+        switch (nilfs_btree_height(btree)) {
+        case 2:
+                bh = NULL;
+                node = root;
+                break;
+        case 3:
+                nchildren = nilfs_btree_node_get_nchildren(btree, root);
+                BUG_ON(nchildren > 1);
+                ptr = nilfs_btree_node_get_ptr(btree, root, nchildren - 1);
+                ret = nilfs_bmap_get_block(bmap, ptr, &bh);
+                if (ret < 0)
+                        return ret;
+                node = (struct nilfs_btree_node *)bh->b_data;
+                break;
+        default:
+                node = NULL;
+                BUG();
+        }
+
+        nchildren = nilfs_btree_node_get_nchildren(btree, node);
+        if (nchildren < nitems)
+                nitems = nchildren;
+        dkeys = nilfs_btree_node_dkeys(btree, node);
+        dptrs = nilfs_btree_node_dptrs(btree, node);
+        for (i = 0; i < nitems; i++) {
+                keys[i] = nilfs_bmap_dkey_to_key(dkeys[i]);
+                ptrs[i] = nilfs_bmap_dptr_to_ptr(dptrs[i]);
+        }
+
+        if (bh != NULL)
+                nilfs_bmap_put_block(bmap, bh);
+
+        return nitems;
+}
+
+static int
+nilfs_btree_prepare_convert_and_insert(struct nilfs_bmap *bmap, __u64 key,
+                                       union nilfs_bmap_ptr_req *dreq,
+                                       union nilfs_bmap_ptr_req *nreq,
+                                       struct buffer_head **bhp,
+                                       struct nilfs_bmap_stats *stats)
+{
+        struct buffer_head *bh;
+        struct nilfs_btree *btree;
+        int ret;
+
+        btree = (struct nilfs_btree *)bmap;
+        stats->bs_nblocks = 0;
+
+        /* for data */
+        /* cannot find near ptr */
+        if (btree->bt_ops->btop_find_target != NULL)
+                dreq->bpr_ptr
+                        = (*btree->bt_ops->btop_find_target)(btree, NULL, key);
+        ret = (*bmap->b_pops->bpop_prepare_alloc_ptr)(bmap, dreq);
+        if (ret < 0)
+                return ret;
+
+        *bhp = NULL;
+        stats->bs_nblocks++;
+        if (nreq != NULL) {
+                nreq->bpr_ptr = dreq->bpr_ptr + 1;
+                ret = (*bmap->b_pops->bpop_prepare_alloc_ptr)(bmap, nreq);
+                if (ret < 0)
+                        goto err_out_dreq;
+
+                ret = nilfs_bmap_get_new_block(bmap, nreq->bpr_ptr, &bh);
+                if (ret < 0)
+                        goto err_out_nreq;
+
+                *bhp = bh;
+                stats->bs_nblocks++;
+        }
+
+        /* success */
+        return 0;
+
+        /* error */
+ err_out_nreq:
+        (*bmap->b_pops->bpop_abort_alloc_ptr)(bmap, nreq);
+ err_out_dreq:
+        (*bmap->b_pops->bpop_abort_alloc_ptr)(bmap, dreq);
+        stats->bs_nblocks = 0;
+        return ret;
+
+}
+
+static void
+nilfs_btree_commit_convert_and_insert(struct nilfs_bmap *bmap,
+                                      __u64 key, __u64 ptr,
+                                      const __u64 *keys, const __u64 *ptrs,
+                                      int n, __u64 low, __u64 high,
+                                      union nilfs_bmap_ptr_req *dreq,
+                                      union nilfs_bmap_ptr_req *nreq,
+                                      struct buffer_head *bh)
+{
+        struct nilfs_btree *btree;
+        struct nilfs_btree_node *node;
+        __u64 tmpptr;
+
+        /* free resources */
+        if (bmap->b_ops->bop_clear != NULL)
+                (*bmap->b_ops->bop_clear)(bmap);
+
+        /* ptr must be a pointer to a buffer head. */
+        set_buffer_nilfs_volatile((struct buffer_head *)((unsigned long)ptr));
+
+        /* convert and insert */
+        btree = (struct nilfs_btree *)bmap;
+        nilfs_btree_init(bmap, low, high);
+        if (nreq != NULL) {
+                if (bmap->b_pops->bpop_commit_alloc_ptr != NULL) {
+                        (*bmap->b_pops->bpop_commit_alloc_ptr)(bmap, dreq);
+                        (*bmap->b_pops->bpop_commit_alloc_ptr)(bmap, nreq);
+                }
+
+                /* create child node at level 1 */
+                lock_buffer(bh);
+                node = (struct nilfs_btree_node *)bh->b_data;
+                nilfs_btree_node_init(btree, node, 0, 1, n, keys, ptrs);
+                nilfs_btree_node_insert(btree, node,
+                                        key, dreq->bpr_ptr, n);
+                if (!buffer_dirty(bh))
+                        nilfs_btnode_mark_dirty(bh);
+                if (!nilfs_bmap_dirty(bmap))
+                        nilfs_bmap_set_dirty(bmap);
+
+                unlock_buffer(bh);
+                nilfs_bmap_put_block(bmap, bh);
+
+                /* create root node at level 2 */
+                node = nilfs_btree_get_root(btree);
+                tmpptr = nreq->bpr_ptr;
+                nilfs_btree_node_init(btree, node, NILFS_BTREE_NODE_ROOT,
+                                      2, 1, &keys[0], &tmpptr);
+        } else {
+                if (bmap->b_pops->bpop_commit_alloc_ptr != NULL)
+                        (*bmap->b_pops->bpop_commit_alloc_ptr)(bmap, dreq);
+
+                /* create root node at level 1 */
+                node = nilfs_btree_get_root(btree);
+                nilfs_btree_node_init(btree, node, NILFS_BTREE_NODE_ROOT,
+                                      1, n, keys, ptrs);
+                nilfs_btree_node_insert(btree, node,
+                                        key, dreq->bpr_ptr, n);
+                if (!nilfs_bmap_dirty(bmap))
+                        nilfs_bmap_set_dirty(bmap);
+        }
+
+        if (btree->bt_ops->btop_set_target != NULL)
+                (*btree->bt_ops->btop_set_target)(btree, key, dreq->bpr_ptr);
+}
+
+/**
+ * nilfs_btree_convert_and_insert -
+ * @bmap:
+ * @key:
+ * @ptr:
+ * @keys:
+ * @ptrs:
+ * @n:
+ * @low:
+ * @high:
+ */
+int nilfs_btree_convert_and_insert(struct nilfs_bmap *bmap,
+                                   __u64 key, __u64 ptr,
+                                   const __u64 *keys, const __u64 *ptrs,
+                                   int n, __u64 low, __u64 high)
+{
+        struct buffer_head *bh;
+        union nilfs_bmap_ptr_req dreq, nreq, *di, *ni;
+        struct nilfs_bmap_stats stats;
+        int ret;
+
+        if (n + 1 <= NILFS_BTREE_ROOT_NCHILDREN_MAX) {
+                di = &dreq;
+                ni = NULL;
+        } else if ((n + 1) <= NILFS_BTREE_NODE_NCHILDREN_MAX(
+                           1 << bmap->b_inode->i_blkbits)) {
+                di = &dreq;
+                ni = &nreq;
+        } else {
+                di = NULL;
+                ni = NULL;
+                BUG();
+        }
+
+        ret = nilfs_btree_prepare_convert_and_insert(bmap, key, di, ni, &bh,
+                                                     &stats);
+        if (ret < 0)
+                return ret;
+        nilfs_btree_commit_convert_and_insert(bmap, key, ptr, keys, ptrs, n,
+                                              low, high, di, ni, bh);
+        nilfs_bmap_add_blocks(bmap, stats.bs_nblocks);
+        return 0;
+}
+
+static int nilfs_btree_propagate_p(struct nilfs_btree *btree,
+                                   struct nilfs_btree_path *path,
+                                   int level,
+                                   struct buffer_head *bh)
+{
+        while ((++level < nilfs_btree_height(btree) - 1) &&
+               !buffer_dirty(path[level].bp_bh))
+                nilfs_btnode_mark_dirty(path[level].bp_bh);
+
+        return 0;
+}
+
+static int nilfs_btree_prepare_update_v(struct nilfs_btree *btree,
+                                        struct nilfs_btree_path *path,
+                                        int level)
+{
+        struct nilfs_btree_node *parent;
+        int ret;
+
+        parent = nilfs_btree_get_node(btree, path, level + 1);
+        path[level].bp_oldreq.bpr_ptr =
+                nilfs_btree_node_get_ptr(btree, parent,
+                                         path[level + 1].bp_index);
+        path[level].bp_newreq.bpr_ptr = path[level].bp_oldreq.bpr_ptr + 1;
+        ret = nilfs_bmap_prepare_update(&btree->bt_bmap,
+                                        &path[level].bp_oldreq,
+                                        &path[level].bp_newreq);
+        if (ret < 0)
+                return ret;
+
+        if (buffer_nilfs_node(path[level].bp_bh)) {
+                path[level].bp_ctxt.oldkey = path[level].bp_oldreq.bpr_ptr;
+                path[level].bp_ctxt.newkey = path[level].bp_newreq.bpr_ptr;
+                path[level].bp_ctxt.bh = path[level].bp_bh;
+                ret = nilfs_btnode_prepare_change_key(
+                        &NILFS_BMAP_I(&btree->bt_bmap)->i_btnode_cache,
+                        &path[level].bp_ctxt);
+                if (ret < 0) {
+                        nilfs_bmap_abort_update(&btree->bt_bmap,
+                                                &path[level].bp_oldreq,
+                                                &path[level].bp_newreq);
+                        return ret;
+                }
+        }
+
+        return 0;
+}
+
+static void nilfs_btree_commit_update_v(struct nilfs_btree *btree,
+                                        struct nilfs_btree_path *path,
+                                        int level)
+{
+        struct nilfs_btree_node *parent;
+
+        nilfs_bmap_commit_update(&btree->bt_bmap,
+                                 &path[level].bp_oldreq,
+                                 &path[level].bp_newreq);
+
+        if (buffer_nilfs_node(path[level].bp_bh)) {
+                nilfs_btnode_commit_change_key(
+                        &NILFS_BMAP_I(&btree->bt_bmap)->i_btnode_cache,
+                        &path[level].bp_ctxt);
+                path[level].bp_bh = path[level].bp_ctxt.bh;
+        }
+        set_buffer_nilfs_volatile(path[level].bp_bh);
+
+        parent = nilfs_btree_get_node(btree, path, level + 1);
+        nilfs_btree_node_set_ptr(btree, parent, path[level + 1].bp_index,
+                                 path[level].bp_newreq.bpr_ptr);
+}
+
+static void nilfs_btree_abort_update_v(struct nilfs_btree *btree,
+                                       struct nilfs_btree_path *path,
+                                       int level)
+{
+        nilfs_bmap_abort_update(&btree->bt_bmap,
+                                &path[level].bp_oldreq,
+                                &path[level].bp_newreq);
+        if (buffer_nilfs_node(path[level].bp_bh))
+                nilfs_btnode_abort_change_key(
+                        &NILFS_BMAP_I(&btree->bt_bmap)->i_btnode_cache,
+                        &path[level].bp_ctxt);
+}
+
+static int nilfs_btree_prepare_propagate_v(struct nilfs_btree *btree,
+                                           struct nilfs_btree_path *path,
+                                           int minlevel,
+                                           int *maxlevelp)
+{
+        int level, ret;
+
+        level = minlevel;
+        if (!buffer_nilfs_volatile(path[level].bp_bh)) {
+                ret = nilfs_btree_prepare_update_v(btree, path, level);
+                if (ret < 0)
+                        return ret;
+        }
+        while ((++level < nilfs_btree_height(btree) - 1) &&
+               !buffer_dirty(path[level].bp_bh)) {
+
+                BUG_ON(buffer_nilfs_volatile(path[level].bp_bh));
+                ret = nilfs_btree_prepare_update_v(btree, path, level);
+                if (ret < 0)
+                        goto out;
+        }
+
+        /* success */
+        BUG_ON(maxlevelp == NULL);
+        *maxlevelp = level - 1;
+        return 0;
+
+        /* error */
+ out:
+        while (--level > minlevel)
+                nilfs_btree_abort_update_v(btree, path, level);
+        if (!buffer_nilfs_volatile(path[level].bp_bh))
+                nilfs_btree_abort_update_v(btree, path, level);
+        return ret;
+}
+
+static void nilfs_btree_commit_propagate_v(struct nilfs_btree *btree,
+                                           struct nilfs_btree_path *path,
+                                           int minlevel,
+                                           int maxlevel,
+                                           struct buffer_head *bh)
+{
+        int level;
+
+        if (!buffer_nilfs_volatile(path[minlevel].bp_bh))
+                nilfs_btree_commit_update_v(btree, path, minlevel);
+
+        for (level = minlevel + 1; level <= maxlevel; level++)
+                nilfs_btree_commit_update_v(btree, path, level);
+}
+
+static int nilfs_btree_propagate_v(struct nilfs_btree *btree,
+                                   struct nilfs_btree_path *path,
+                                   int level,
+                                   struct buffer_head *bh)
+{
+        int maxlevel, ret;
+        struct nilfs_btree_node *parent;
+        __u64 ptr;
+
+        get_bh(bh);
+        path[level].bp_bh = bh;
+        ret = nilfs_btree_prepare_propagate_v(btree, path, level, &maxlevel);
+        if (ret < 0)
+                goto out;
+
+        if (buffer_nilfs_volatile(path[level].bp_bh)) {
+                parent = nilfs_btree_get_node(btree, path, level + 1);
+                ptr = nilfs_btree_node_get_ptr(btree, parent,
+                                               path[level + 1].bp_index);
+                ret = nilfs_bmap_mark_dirty(&btree->bt_bmap, ptr);
+                if (ret < 0)
+                        goto out;
+        }
+
+        nilfs_btree_commit_propagate_v(btree, path, level, maxlevel, bh);
+
+ out:
+        brelse(path[level].bp_bh);
+        path[level].bp_bh = NULL;
+        return ret;
+}
+
+static int nilfs_btree_propagate(const struct nilfs_bmap *bmap,
+                                 struct buffer_head *bh)
+{
+        struct nilfs_btree *btree;
+        struct nilfs_btree_path *path;
+        struct nilfs_btree_node *node;
+        __u64 key;
+        int level, ret;
+
+        BUG_ON(!buffer_dirty(bh));
+
+        btree = (struct nilfs_btree *)bmap;
+        path = nilfs_btree_alloc_path(btree);
+        if (path == NULL)
+                return -ENOMEM;
+        nilfs_btree_init_path(btree, path);
+
+        if (buffer_nilfs_node(bh)) {
+                node = (struct nilfs_btree_node *)bh->b_data;
+                key = nilfs_btree_node_get_key(btree, node, 0);
+                level = nilfs_btree_node_get_level(btree, node);
+        } else {
+                key = nilfs_bmap_data_get_key(bmap, bh);
+                level = NILFS_BTREE_LEVEL_DATA;
+        }
+
+        ret = nilfs_btree_do_lookup(btree, path, key, NULL, level + 1);
+        if (ret < 0) {
+                /* BUG_ON(ret == -ENOENT); */
+                if (ret == -ENOENT) {
+                        printk(KERN_CRIT "%s: key = %llu, level == %d\n",
+                               __func__, (unsigned long long)key, level);
+                        BUG();
+                }
+                goto out;
+        }
+
+        ret = (*btree->bt_ops->btop_propagate)(btree, path, level, bh);
+
+ out:
+        nilfs_btree_clear_path(btree, path);
+        nilfs_btree_free_path(btree, path);
+
+        return ret;
+}
+
+static int nilfs_btree_propagate_gc(const struct nilfs_bmap *bmap,
+                                    struct buffer_head *bh)
+{
+        return nilfs_bmap_mark_dirty(bmap, bh->b_blocknr);
+}
+
+static void nilfs_btree_add_dirty_buffer(struct nilfs_btree *btree,
+                                         struct list_head *lists,
+                                         struct buffer_head *bh)
+{
+        struct list_head *head;
+        struct buffer_head *cbh;
+        struct nilfs_btree_node *node, *cnode;
+        __u64 key, ckey;
+        int level;
+
+        get_bh(bh);
+        node = (struct nilfs_btree_node *)bh->b_data;
+        key = nilfs_btree_node_get_key(btree, node, 0);
+        level = nilfs_btree_node_get_level(btree, node);
+        list_for_each(head, &lists[level]) {
+                cbh = list_entry(head, struct buffer_head, b_assoc_buffers);
+                cnode = (struct nilfs_btree_node *)cbh->b_data;
+                ckey = nilfs_btree_node_get_key(btree, cnode, 0);
+                if (key < ckey)
+                        break;
+        }
+        list_add_tail(&bh->b_assoc_buffers, head);
+}
+
+static void nilfs_btree_lookup_dirty_buffers(struct nilfs_bmap *bmap,
+                                             struct list_head *listp)
+{
+        struct nilfs_btree *btree = (struct nilfs_btree *)bmap;
+        struct address_space *btcache = &NILFS_BMAP_I(bmap)->i_btnode_cache;
+        struct list_head lists[NILFS_BTREE_LEVEL_MAX];
+        struct pagevec pvec;
+        struct buffer_head *bh, *head;
+        pgoff_t index = 0;
+        int level, i;
+
+        for (level = NILFS_BTREE_LEVEL_NODE_MIN;
+             level < NILFS_BTREE_LEVEL_MAX;
+             level++)
+                INIT_LIST_HEAD(&lists[level]);
+
+        pagevec_init(&pvec, 0);
+
+        while (pagevec_lookup_tag(&pvec, btcache, &index, PAGECACHE_TAG_DIRTY,
+                                  PAGEVEC_SIZE)) {
+                for (i = 0; i < pagevec_count(&pvec); i++) {
+                        bh = head = page_buffers(pvec.pages[i]);
+                        do {
+                                if (buffer_dirty(bh))
+                                        nilfs_btree_add_dirty_buffer(btree,
+                                                                     lists, bh);
+                        } while ((bh = bh->b_this_page) != head);
+                }
+                pagevec_release(&pvec);
+                cond_resched();
+        }
+
+        for (level = NILFS_BTREE_LEVEL_NODE_MIN;
+             level < NILFS_BTREE_LEVEL_MAX;
+             level++)
+                list_splice(&lists[level], listp->prev);
+}
+
+static int nilfs_btree_assign_p(struct nilfs_btree *btree,
+                                struct nilfs_btree_path *path,
+                                int level,
+                                struct buffer_head **bh,
+                                sector_t blocknr,
+                                union nilfs_binfo *binfo)
+{
+        struct nilfs_btree_node *parent;
+        __u64 key;
+        __u64 ptr;
+        int ret;
+
+        parent = nilfs_btree_get_node(btree, path, level + 1);
+        ptr = nilfs_btree_node_get_ptr(btree, parent,
+                                       path[level + 1].bp_index);
+        if (buffer_nilfs_node(*bh)) {
+                path[level].bp_ctxt.oldkey = ptr;
+                path[level].bp_ctxt.newkey = blocknr;
+                path[level].bp_ctxt.bh = *bh;
+                ret = nilfs_btnode_prepare_change_key(
+                        &NILFS_BMAP_I(&btree->bt_bmap)->i_btnode_cache,
+                        &path[level].bp_ctxt);
+                if (ret < 0)
+                        return ret;
+                nilfs_btnode_commit_change_key(
+                        &NILFS_BMAP_I(&btree->bt_bmap)->i_btnode_cache,
+                        &path[level].bp_ctxt);
+                *bh = path[level].bp_ctxt.bh;
+        }
+
+        nilfs_btree_node_set_ptr(btree, parent,
+                                 path[level + 1].bp_index, blocknr);
+
+        key = nilfs_btree_node_get_key(btree, parent,
+                                       path[level + 1].bp_index);
+        /* on-disk format */
+        binfo->bi_dat.bi_blkoff = nilfs_bmap_key_to_dkey(key);
+        binfo->bi_dat.bi_level = level;
+
+        return 0;
+}
+
+static int nilfs_btree_assign_v(struct nilfs_btree *btree,
+                                struct nilfs_btree_path *path,
+                                int level,
+                                struct buffer_head **bh,
+                                sector_t blocknr,
+                                union nilfs_binfo *binfo)
+{
+        struct nilfs_btree_node *parent;
+        __u64 key;
+        __u64 ptr;
+        union nilfs_bmap_ptr_req req;
+        int ret;
+
+        parent = nilfs_btree_get_node(btree, path, level + 1);
+        ptr = nilfs_btree_node_get_ptr(btree, parent,
+                                       path[level + 1].bp_index);
+        req.bpr_ptr = ptr;
+        ret = (*btree->bt_bmap.b_pops->bpop_prepare_start_ptr)(&btree->bt_bmap,
+                                                               &req);
+        if (ret < 0)
+                return ret;
+        (*btree->bt_bmap.b_pops->bpop_commit_start_ptr)(&btree->bt_bmap,
+                                                        &req, blocknr);
+
+        key = nilfs_btree_node_get_key(btree, parent,
+                                       path[level + 1].bp_index);
+        /* on-disk format */
+        binfo->bi_v.bi_vblocknr = nilfs_bmap_ptr_to_dptr(ptr);
+        binfo->bi_v.bi_blkoff = nilfs_bmap_key_to_dkey(key);
+
+        return 0;
+}
+
+static int nilfs_btree_assign(struct nilfs_bmap *bmap,
+                              struct buffer_head **bh,
+                              sector_t blocknr,
+                              union nilfs_binfo *binfo)
+{
+        struct nilfs_btree *btree;
+        struct nilfs_btree_path *path;
+        struct nilfs_btree_node *node;
+        __u64 key;
+        int level, ret;
+
+        btree = (struct nilfs_btree *)bmap;
+        path = nilfs_btree_alloc_path(btree);
+        if (path == NULL)
+                return -ENOMEM;
+        nilfs_btree_init_path(btree, path);
+
+        if (buffer_nilfs_node(*bh)) {
+                node = (struct nilfs_btree_node *)(*bh)->b_data;
+                key = nilfs_btree_node_get_key(btree, node, 0);
+                level = nilfs_btree_node_get_level(btree, node);
+        } else {
+                key = nilfs_bmap_data_get_key(bmap, *bh);
+                level = NILFS_BTREE_LEVEL_DATA;
+        }
+
+        ret = nilfs_btree_do_lookup(btree, path, key, NULL, level + 1);
+        if (ret < 0) {
+                BUG_ON(ret == -ENOENT);
+                goto out;
+        }
+
+        ret = (*btree->bt_ops->btop_assign)(btree, path, level, bh,
+                                            blocknr, binfo);
+
+ out:
+        nilfs_btree_clear_path(btree, path);
+        nilfs_btree_free_path(btree, path);
+
+        return ret;
+}
+
+static int nilfs_btree_assign_gc(struct nilfs_bmap *bmap,
+                                 struct buffer_head **bh,
+                                 sector_t blocknr,
+                                 union nilfs_binfo *binfo)
+{
+        struct nilfs_btree *btree;
+        struct nilfs_btree_node *node;
+        __u64 key;
+        int ret;
+
+        btree = (struct nilfs_btree *)bmap;
+        ret = nilfs_bmap_move_v(bmap, (*bh)->b_blocknr, blocknr);
+        if (ret < 0)
+                return ret;
+
+        if (buffer_nilfs_node(*bh)) {
+                node = (struct nilfs_btree_node *)(*bh)->b_data;
+                key = nilfs_btree_node_get_key(btree, node, 0);
+        } else
+                key = nilfs_bmap_data_get_key(bmap, *bh);
+
+        /* on-disk format */
+        binfo->bi_v.bi_vblocknr = cpu_to_le64((*bh)->b_blocknr);
+        binfo->bi_v.bi_blkoff = nilfs_bmap_key_to_dkey(key);
+
+        return 0;
+}
+
+static int nilfs_btree_mark(struct nilfs_bmap *bmap, __u64 key, int level)
+{
+        struct buffer_head *bh;
+        struct nilfs_btree *btree;
+        struct nilfs_btree_path *path;
+        __u64 ptr;
+        int ret;
+
+        btree = (struct nilfs_btree *)bmap;
+        path = nilfs_btree_alloc_path(btree);
+        if (path == NULL)
+                return -ENOMEM;
+        nilfs_btree_init_path(btree, path);
+
+        ret = nilfs_btree_do_lookup(btree, path, key, &ptr, level + 1);
+        if (ret < 0) {
+                BUG_ON(ret == -ENOENT);
+                goto out;
+        }
+        ret = nilfs_bmap_get_block(&btree->bt_bmap, ptr, &bh);
+        if (ret < 0) {
+                BUG_ON(ret == -ENOENT);
+                goto out;
+        }
+
+        if (!buffer_dirty(bh))
+                nilfs_btnode_mark_dirty(bh);
+        nilfs_bmap_put_block(&btree->bt_bmap, bh);
+        if (!nilfs_bmap_dirty(&btree->bt_bmap))
+                nilfs_bmap_set_dirty(&btree->bt_bmap);
+
+ out:
+        nilfs_btree_clear_path(btree, path);
+        nilfs_btree_free_path(btree, path);
+        return ret;
+}
+
+static const struct nilfs_bmap_operations nilfs_btree_ops = {
+        .bop_lookup             =       nilfs_btree_lookup,
+        .bop_insert             =       nilfs_btree_insert,
+        .bop_delete             =       nilfs_btree_delete,
+        .bop_clear              =       NULL,
+
+        .bop_propagate          =       nilfs_btree_propagate,
+
+        .bop_lookup_dirty_buffers =     nilfs_btree_lookup_dirty_buffers,
+
+        .bop_assign             =       nilfs_btree_assign,
+        .bop_mark               =       nilfs_btree_mark,
+
+        .bop_last_key           =       nilfs_btree_last_key,
+        .bop_check_insert       =       NULL,
+        .bop_check_delete       =       nilfs_btree_check_delete,
+        .bop_gather_data        =       nilfs_btree_gather_data,
+};
+
+static const struct nilfs_bmap_operations nilfs_btree_ops_gc = {
+        .bop_lookup             =       NULL,
+        .bop_insert             =       NULL,
+        .bop_delete             =       NULL,
+        .bop_clear              =       NULL,
+
+        .bop_propagate          =       nilfs_btree_propagate_gc,
+
+        .bop_lookup_dirty_buffers =     nilfs_btree_lookup_dirty_buffers,
+
+        .bop_assign             =       nilfs_btree_assign_gc,
+        .bop_mark               =       NULL,
+
+        .bop_last_key           =       NULL,
+        .bop_check_insert       =       NULL,
+        .bop_check_delete       =       NULL,
+        .bop_gather_data        =       NULL,
+};
+
+static const struct nilfs_btree_operations nilfs_btree_ops_v = {
+        .btop_find_target       =       nilfs_btree_find_target_v,
+        .btop_set_target        =       nilfs_btree_set_target_v,
+        .btop_propagate         =       nilfs_btree_propagate_v,
+        .btop_assign            =       nilfs_btree_assign_v,
+};
+
+static const struct nilfs_btree_operations nilfs_btree_ops_p = {
+        .btop_find_target       =       NULL,
+        .btop_set_target        =       NULL,
+        .btop_propagate         =       nilfs_btree_propagate_p,
+        .btop_assign            =       nilfs_btree_assign_p,
+};
+
+int nilfs_btree_init(struct nilfs_bmap *bmap, __u64 low, __u64 high)
+{
+        struct nilfs_btree *btree;
+
+        btree = (struct nilfs_btree *)bmap;
+        bmap->b_ops = &nilfs_btree_ops;
+        bmap->b_low = low;
+        bmap->b_high = high;
+        switch (bmap->b_inode->i_ino) {
+        case NILFS_DAT_INO:
+                btree->bt_ops = &nilfs_btree_ops_p;
+                break;
+        default:
+                btree->bt_ops = &nilfs_btree_ops_v;
+                break;
+        }
+
+        return 0;
+}
+
+void nilfs_btree_init_gc(struct nilfs_bmap *bmap)
+{
+        bmap->b_low = NILFS_BMAP_LARGE_LOW;
+        bmap->b_high = NILFS_BMAP_LARGE_HIGH;
+        bmap->b_ops = &nilfs_btree_ops_gc;
+}
diff --git a/fs/nilfs2/btree.h b/fs/nilfs2/btree.h
new file mode 100644
index 000000000000..4766deb52fb1
--- /dev/null
+++ b/fs/nilfs2/btree.h
@@ -0,0 +1,117 @@
+/*
+ * btree.h - 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>.
+ */
+
+#ifndef _NILFS_BTREE_H
+#define _NILFS_BTREE_H
+
+#include <linux/types.h>
+#include <linux/buffer_head.h>
+#include <linux/list.h>
+#include <linux/nilfs2_fs.h>
+#include "btnode.h"
+#include "bmap.h"
+
+struct nilfs_btree;
+struct nilfs_btree_path;
+
+/**
+ * struct nilfs_btree_operations - B-tree operation table
+ */
+struct nilfs_btree_operations {
+        __u64 (*btop_find_target)(const struct nilfs_btree *,
+                                  const struct nilfs_btree_path *, __u64);
+        void (*btop_set_target)(struct nilfs_btree *, __u64, __u64);
+
+        struct the_nilfs *(*btop_get_nilfs)(struct nilfs_btree *);
+
+        int (*btop_propagate)(struct nilfs_btree *,
+                              struct nilfs_btree_path *,
+                              int,
+                              struct buffer_head *);
+        int (*btop_assign)(struct nilfs_btree *,
+                           struct nilfs_btree_path *,
+                           int,
+                           struct buffer_head **,
+                           sector_t,
+                           union nilfs_binfo *);
+};
+
+/**
+ * struct nilfs_btree_node - B-tree node
+ * @bn_flags: flags
+ * @bn_level: level
+ * @bn_nchildren: number of children
+ * @bn_pad: padding
+ */
+struct nilfs_btree_node {
+        __u8 bn_flags;
+        __u8 bn_level;
+        __le16 bn_nchildren;
+        __le32 bn_pad;
+};
+
+/* flags */
+#define NILFS_BTREE_NODE_ROOT   0x01
+
+/* level */
+#define NILFS_BTREE_LEVEL_DATA          0
+#define NILFS_BTREE_LEVEL_NODE_MIN      (NILFS_BTREE_LEVEL_DATA + 1)
+#define NILFS_BTREE_LEVEL_MAX           14
+
+/**
+ * struct nilfs_btree - B-tree structure
+ * @bt_bmap: bmap base structure
+ * @bt_ops: B-tree operation table
+ */
+struct nilfs_btree {
+        struct nilfs_bmap bt_bmap;
+
+        /* B-tree-specific members */
+        const struct nilfs_btree_operations *bt_ops;
+};
+
+
+#define NILFS_BTREE_ROOT_SIZE           NILFS_BMAP_SIZE
+#define NILFS_BTREE_ROOT_NCHILDREN_MAX                                  \
+        ((NILFS_BTREE_ROOT_SIZE - sizeof(struct nilfs_btree_node)) /    \
+         (sizeof(__le64 /* dkey */) + sizeof(__le64 /* dptr */)))
+#define NILFS_BTREE_ROOT_NCHILDREN_MIN  0
+#define NILFS_BTREE_NODE_EXTRA_PAD_SIZE (sizeof(__le64))
+#define NILFS_BTREE_NODE_NCHILDREN_MAX(nodesize)                        \
+        (((nodesize) - sizeof(struct nilfs_btree_node) -                \
+                NILFS_BTREE_NODE_EXTRA_PAD_SIZE) /                      \
+         (sizeof(__le64 /* dkey */) + sizeof(__le64 /* dptr */)))
+#define NILFS_BTREE_NODE_NCHILDREN_MIN(nodesize)                        \
+        ((NILFS_BTREE_NODE_NCHILDREN_MAX(nodesize) - 1) / 2 + 1)
+#define NILFS_BTREE_KEY_MIN     ((__u64)0)
+#define NILFS_BTREE_KEY_MAX     (~(__u64)0)
+
+
+int nilfs_btree_path_cache_init(void);
+void nilfs_btree_path_cache_destroy(void);
+int nilfs_btree_init(struct nilfs_bmap *, __u64, __u64);
+int nilfs_btree_convert_and_insert(struct nilfs_bmap *, __u64, __u64,
+                                   const __u64 *, const __u64 *,
+                                   int, __u64, __u64);
+void nilfs_btree_init_gc(struct nilfs_bmap *);
+
+#endif  /* _NILFS_BTREE_H */