nilfs2: unify bmap operations starting use of indirect block address

[linux-2.6] / fs / nilfs2 / btree.c

/*
 * 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:
        *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;

        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 {
                        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_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 */
                        WARN_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);
                WARN_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;
                return -EINVAL;
        }

        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)) {

                WARN_ON(buffer_nilfs_volatile(path[level].bp_bh));
                ret = nilfs_btree_prepare_update_v(btree, path, level);
                if (ret < 0)
                        goto out;
        }

        /* success */
        *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;

        WARN_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) {
                if (unlikely(ret == -ENOENT))
                        printk(KERN_CRIT "%s: key = %llu, level == %d\n",
                               __func__, (unsigned long long)key, level);
                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 = nilfs_bmap_start_v(&btree->bt_bmap, &req, blocknr);
        if (unlikely(ret < 0))
                return ret;

        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) {
                WARN_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) {
                WARN_ON(ret == -ENOENT);
                goto out;
        }
        ret = nilfs_bmap_get_block(&btree->bt_bmap, ptr, &bh);
        if (ret < 0) {
                WARN_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;
}