btree.c

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/*
 * 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 <[email protected]>.
 */

#include <linux/slab.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/pagevec.h>
#include "nilfs.h"
#include "page.h"
#include "btnode.h"
#include "btree.h"
#include "alloc.h"
#include "dat.h"

static struct nilfs_btree_path *nilfs_btree_alloc_path(void)
{
    struct nilfs_btree_path *path;
    int level = NILFS_BTREE_LEVEL_DATA;

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

    for (; level < NILFS_BTREE_LEVEL_MAX; level++) {
        path[level].bp_bh = NULL;
        path[level].bp_sib_bh = NULL;
        path[level].bp_index = 0;
        path[level].bp_oldreq.bpr_ptr = NILFS_BMAP_INVALID_PTR;
        path[level].bp_newreq.bpr_ptr = NILFS_BMAP_INVALID_PTR;
        path[level].bp_op = NULL;
    }

out:
    return path;
}

static void nilfs_btree_free_path(struct nilfs_btree_path *path)
{
    int level = NILFS_BTREE_LEVEL_DATA;

    for (; level < NILFS_BTREE_LEVEL_MAX; level++)
        brelse(path[level].bp_bh);

    kmem_cache_free(nilfs_btree_path_cache, path);
}

/*
 * B-tree node operations
 */
static int nilfs_btree_get_new_block(const struct nilfs_bmap *btree,
                     __u64 ptr, struct buffer_head **bhp)
{
    struct address_space *btnc = &NILFS_BMAP_I(btree)->i_btnode_cache;
    struct buffer_head *bh;

    bh = nilfs_btnode_create_block(btnc, ptr);
    if (!bh)
        return -ENOMEM;

    set_buffer_nilfs_volatile(bh);
    *bhp = bh;
    return 0;
}

static int nilfs_btree_node_get_flags(const struct nilfs_btree_node *node)
{
    return node->bn_flags;
}

static void
nilfs_btree_node_set_flags(struct nilfs_btree_node *node, int flags)
{
    node->bn_flags = flags;
}

static int nilfs_btree_node_root(const struct nilfs_btree_node *node)
{
    return nilfs_btree_node_get_flags(node) & NILFS_BTREE_NODE_ROOT;
}

static int nilfs_btree_node_get_level(const struct nilfs_btree_node *node)
{
    return node->bn_level;
}

static void
nilfs_btree_node_set_level(struct nilfs_btree_node *node, int level)
{
    node->bn_level = level;
}

static int nilfs_btree_node_get_nchildren(const struct nilfs_btree_node *node)
{
    return le16_to_cpu(node->bn_nchildren);
}

static void
nilfs_btree_node_set_nchildren(struct nilfs_btree_node *node, int nchildren)
{
    node->bn_nchildren = cpu_to_le16(nchildren);
}

static int nilfs_btree_node_size(const struct nilfs_bmap *btree)
{
    return 1 << btree->b_inode->i_blkbits;
}

static int nilfs_btree_nchildren_per_block(const struct nilfs_bmap *btree)
{
    return btree->b_nchildren_per_block;
}

static __le64 *
nilfs_btree_node_dkeys(const struct nilfs_btree_node *node)
{
    return (__le64 *)((char *)(node + 1) +
              (nilfs_btree_node_root(node) ?
               0 : NILFS_BTREE_NODE_EXTRA_PAD_SIZE));
}

static __le64 *
nilfs_btree_node_dptrs(const struct nilfs_btree_node *node, int ncmax)
{
    return (__le64 *)(nilfs_btree_node_dkeys(node) + ncmax);
}

static __u64
nilfs_btree_node_get_key(const struct nilfs_btree_node *node, int index)
{
    return le64_to_cpu(*(nilfs_btree_node_dkeys(node) + index));
}

static void
nilfs_btree_node_set_key(struct nilfs_btree_node *node, int index, __u64 key)
{
    *(nilfs_btree_node_dkeys(node) + index) = cpu_to_le64(key);
}

static __u64
nilfs_btree_node_get_ptr(const struct nilfs_btree_node *node, int index,
             int ncmax)
{
    return le64_to_cpu(*(nilfs_btree_node_dptrs(node, ncmax) + index));
}

static void
nilfs_btree_node_set_ptr(struct nilfs_btree_node *node, int index, __u64 ptr,
             int ncmax)
{
    *(nilfs_btree_node_dptrs(node, ncmax) + index) = cpu_to_le64(ptr);
}

static void nilfs_btree_node_init(struct nilfs_btree_node *node, int flags,
                  int level, int nchildren, int ncmax,
                  const __u64 *keys, const __u64 *ptrs)
{
    __le64 *dkeys;
    __le64 *dptrs;
    int i;

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

    dkeys = nilfs_btree_node_dkeys(node);
    dptrs = nilfs_btree_node_dptrs(node, ncmax);
    for (i = 0; i < nchildren; i++) {
        dkeys[i] = cpu_to_le64(keys[i]);
        dptrs[i] = cpu_to_le64(ptrs[i]);
    }
}

/* Assume the buffer heads corresponding to left and right are locked. */
static void nilfs_btree_node_move_left(struct nilfs_btree_node *left,
                       struct nilfs_btree_node *right,
                       int n, int lncmax, int rncmax)
{
    __le64 *ldkeys, *rdkeys;
    __le64 *ldptrs, *rdptrs;
    int lnchildren, rnchildren;

    ldkeys = nilfs_btree_node_dkeys(left);
    ldptrs = nilfs_btree_node_dptrs(left, lncmax);
    lnchildren = nilfs_btree_node_get_nchildren(left);

    rdkeys = nilfs_btree_node_dkeys(right);
    rdptrs = nilfs_btree_node_dptrs(right, rncmax);
    rnchildren = nilfs_btree_node_get_nchildren(right);

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

    lnchildren += n;
    rnchildren -= n;
    nilfs_btree_node_set_nchildren(left, lnchildren);
    nilfs_btree_node_set_nchildren(right, rnchildren);
}

/* Assume that the buffer heads corresponding to left and right are locked. */
static void nilfs_btree_node_move_right(struct nilfs_btree_node *left,
                    struct nilfs_btree_node *right,
                    int n, int lncmax, int rncmax)
{
    __le64 *ldkeys, *rdkeys;
    __le64 *ldptrs, *rdptrs;
    int lnchildren, rnchildren;

    ldkeys = nilfs_btree_node_dkeys(left);
    ldptrs = nilfs_btree_node_dptrs(left, lncmax);
    lnchildren = nilfs_btree_node_get_nchildren(left);

    rdkeys = nilfs_btree_node_dkeys(right);
    rdptrs = nilfs_btree_node_dptrs(right, rncmax);
    rnchildren = nilfs_btree_node_get_nchildren(right);

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

    lnchildren -= n;
    rnchildren += n;
    nilfs_btree_node_set_nchildren(left, lnchildren);
    nilfs_btree_node_set_nchildren(right, rnchildren);
}

/* Assume that the buffer head corresponding to node is locked. */
static void nilfs_btree_node_insert(struct nilfs_btree_node *node, int index,
                    __u64 key, __u64 ptr, int ncmax)
{
    __le64 *dkeys;
    __le64 *dptrs;
    int nchildren;

    dkeys = nilfs_btree_node_dkeys(node);
    dptrs = nilfs_btree_node_dptrs(node, ncmax);
    nchildren = nilfs_btree_node_get_nchildren(node);
    if (index < nchildren) {
        memmove(dkeys + index + 1, dkeys + index,
            (nchildren - index) * sizeof(*dkeys));
        memmove(dptrs + index + 1, dptrs + index,
            (nchildren - index) * sizeof(*dptrs));
    }
    dkeys[index] = cpu_to_le64(key);
    dptrs[index] = cpu_to_le64(ptr);
    nchildren++;
    nilfs_btree_node_set_nchildren(node, nchildren);
}

/* Assume that the buffer head corresponding to node is locked. */
static void nilfs_btree_node_delete(struct nilfs_btree_node *node, int index,
                    __u64 *keyp, __u64 *ptrp, int ncmax)
{
    __u64 key;
    __u64 ptr;
    __le64 *dkeys;
    __le64 *dptrs;
    int nchildren;

    dkeys = nilfs_btree_node_dkeys(node);
    dptrs = nilfs_btree_node_dptrs(node, ncmax);
    key = le64_to_cpu(dkeys[index]);
    ptr = le64_to_cpu(dptrs[index]);
    nchildren = nilfs_btree_node_get_nchildren(node);
    if (keyp != NULL)
        *keyp = key;
    if (ptrp != NULL)
        *ptrp = ptr;

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

static int nilfs_btree_node_lookup(const struct nilfs_btree_node *node,
                   __u64 key, int *indexp)
{
    __u64 nkey;
    int index, low, high, s;

    /* binary search */
    low = 0;
    high = nilfs_btree_node_get_nchildren(node) - 1;
    index = 0;
    s = 0;
    while (low <= high) {
        index = (low + high) / 2;
        nkey = nilfs_btree_node_get_key(node, index);
        if (nkey == key) {
            s = 0;
            goto out;
        } else if (nkey < key) {
            low = index + 1;
            s = -1;
        } else {
            high = index - 1;
            s = 1;
        }
    }

    /* adjust index */
    if (nilfs_btree_node_get_level(node) > NILFS_BTREE_LEVEL_NODE_MIN) {
        if (s > 0 && index > 0)
            index--;
    } else if (s < 0)
        index++;

 out:
    *indexp = index;

    return s == 0;
}

static int nilfs_btree_node_broken(const struct nilfs_btree_node *node,
                   size_t size, sector_t blocknr)
{
    int level, flags, nchildren;
    int ret = 0;

    level = nilfs_btree_node_get_level(node);
    flags = nilfs_btree_node_get_flags(node);
    nchildren = nilfs_btree_node_get_nchildren(node);

    if (unlikely(level < NILFS_BTREE_LEVEL_NODE_MIN ||
             level >= NILFS_BTREE_LEVEL_MAX ||
             (flags & NILFS_BTREE_NODE_ROOT) ||
             nchildren < 0 ||
             nchildren > NILFS_BTREE_NODE_NCHILDREN_MAX(size))) {
        printk(KERN_CRIT "NILFS: bad btree node (blocknr=%llu): "
               "level = %d, flags = 0x%x, nchildren = %d\n",
               (unsigned long long)blocknr, level, flags, nchildren);
        ret = 1;
    }
    return ret;
}

int nilfs_btree_broken_node_block(struct buffer_head *bh)
{
    int ret;

    if (buffer_nilfs_checked(bh))
        return 0;

    ret = nilfs_btree_node_broken((struct nilfs_btree_node *)bh->b_data,
                       bh->b_size, bh->b_blocknr);
    if (likely(!ret))
        set_buffer_nilfs_checked(bh);
    return ret;
}

static struct nilfs_btree_node *
nilfs_btree_get_root(const struct nilfs_bmap *btree)
{
    return (struct nilfs_btree_node *)btree->b_u.u_data;
}

static struct nilfs_btree_node *
nilfs_btree_get_nonroot_node(const struct nilfs_btree_path *path, int level)
{
    return (struct nilfs_btree_node *)path[level].bp_bh->b_data;
}

static struct nilfs_btree_node *
nilfs_btree_get_sib_node(const struct nilfs_btree_path *path, int level)
{
    return (struct nilfs_btree_node *)path[level].bp_sib_bh->b_data;
}

static int nilfs_btree_height(const struct nilfs_bmap *btree)
{
    return nilfs_btree_node_get_level(nilfs_btree_get_root(btree)) + 1;
}

static struct nilfs_btree_node *
nilfs_btree_get_node(const struct nilfs_bmap *btree,
             const struct nilfs_btree_path *path,
             int level, int *ncmaxp)
{
    struct nilfs_btree_node *node;

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

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

struct nilfs_btree_readahead_info {
    struct nilfs_btree_node *node;  /* parent node */
    int max_ra_blocks;      /* max nof blocks to read ahead */
    int index;          /* current index on the parent node */
    int ncmax;          /* nof children in the parent node */
};

static int __nilfs_btree_get_block(const struct nilfs_bmap *btree, __u64 ptr,
                   struct buffer_head **bhp,
                   const struct nilfs_btree_readahead_info *ra)
{
    struct address_space *btnc = &NILFS_BMAP_I(btree)->i_btnode_cache;
    struct buffer_head *bh, *ra_bh;
    sector_t submit_ptr = 0;
    int ret;

    ret = nilfs_btnode_submit_block(btnc, ptr, 0, READ, &bh, &submit_ptr);
    if (ret) {
        if (ret != -EEXIST)
            return ret;
        goto out_check;
    }

    if (ra) {
        int i, n;
        __u64 ptr2;

        /* read ahead sibling nodes */
        for (n = ra->max_ra_blocks, i = ra->index + 1;
             n > 0 && i < ra->ncmax; n--, i++) {
            ptr2 = nilfs_btree_node_get_ptr(ra->node, i, ra->ncmax);

            ret = nilfs_btnode_submit_block(btnc, ptr2, 0, READA,
                            &ra_bh, &submit_ptr);
            if (likely(!ret || ret == -EEXIST))
                brelse(ra_bh);
            else if (ret != -EBUSY)
                break;
            if (!buffer_locked(bh))
                goto out_no_wait;
        }
    }

    wait_on_buffer(bh);

 out_no_wait:
    if (!buffer_uptodate(bh)) {
        brelse(bh);
        return -EIO;
    }

 out_check:
    if (nilfs_btree_broken_node_block(bh)) {
        clear_buffer_uptodate(bh);
        brelse(bh);
        return -EINVAL;
    }

    *bhp = bh;
    return 0;
}

static int nilfs_btree_get_block(const struct nilfs_bmap *btree, __u64 ptr,
                   struct buffer_head **bhp)
{
    return __nilfs_btree_get_block(btree, ptr, bhp, NULL);
}

static int nilfs_btree_do_lookup(const struct nilfs_bmap *btree,
                 struct nilfs_btree_path *path,
                 __u64 key, __u64 *ptrp, int minlevel,
                 int readahead)
{
    struct nilfs_btree_node *node;
    struct nilfs_btree_readahead_info p, *ra;
    __u64 ptr;
    int level, index, found, ncmax, ret;

    node = nilfs_btree_get_root(btree);
    level = nilfs_btree_node_get_level(node);
    if (level < minlevel || nilfs_btree_node_get_nchildren(node) <= 0)
        return -ENOENT;

    found = nilfs_btree_node_lookup(node, key, &index);
    ptr = nilfs_btree_node_get_ptr(node, index,
                       NILFS_BTREE_ROOT_NCHILDREN_MAX);
    path[level].bp_bh = NULL;
    path[level].bp_index = index;

    ncmax = nilfs_btree_nchildren_per_block(btree);

    while (--level >= minlevel) {
        ra = NULL;
        if (level == NILFS_BTREE_LEVEL_NODE_MIN && readahead) {
            p.node = nilfs_btree_get_node(btree, path, level + 1,
                              &p.ncmax);
            p.index = index;
            p.max_ra_blocks = 7;
            ra = &p;
        }
        ret = __nilfs_btree_get_block(btree, ptr, &path[level].bp_bh,
                          ra);
        if (ret < 0)
            return ret;

        node = nilfs_btree_get_nonroot_node(path, level);
        if (nilfs_btree_bad_node(node, level))
            return -EINVAL;
        if (!found)
            found = nilfs_btree_node_lookup(node, key, &index);
        else
            index = 0;
        if (index < ncmax) {
            ptr = nilfs_btree_node_get_ptr(node, index, ncmax);
        } else {
            WARN_ON(found || level != NILFS_BTREE_LEVEL_NODE_MIN);
            /* insert */
            ptr = NILFS_BMAP_INVALID_PTR;
        }
        path[level].bp_index = index;
    }
    if (!found)
        return -ENOENT;

    if (ptrp != NULL)
        *ptrp = ptr;

    return 0;
}

static int nilfs_btree_do_lookup_last(const struct nilfs_bmap *btree,
                      struct nilfs_btree_path *path,
                      __u64 *keyp, __u64 *ptrp)
{
    struct nilfs_btree_node *node;
    __u64 ptr;
    int index, level, ncmax, ret;

    node = nilfs_btree_get_root(btree);
    index = nilfs_btree_node_get_nchildren(node) - 1;
    if (index < 0)
        return -ENOENT;
    level = nilfs_btree_node_get_level(node);
    ptr = nilfs_btree_node_get_ptr(node, index,
                       NILFS_BTREE_ROOT_NCHILDREN_MAX);
    path[level].bp_bh = NULL;
    path[level].bp_index = index;
    ncmax = nilfs_btree_nchildren_per_block(btree);

    for (level--; level > 0; level--) {
        ret = nilfs_btree_get_block(btree, ptr, &path[level].bp_bh);
        if (ret < 0)
            return ret;
        node = nilfs_btree_get_nonroot_node(path, level);
        if (nilfs_btree_bad_node(node, level))
            return -EINVAL;
        index = nilfs_btree_node_get_nchildren(node) - 1;
        ptr = nilfs_btree_node_get_ptr(node, index, ncmax);
        path[level].bp_index = index;
    }

    if (keyp != NULL)
        *keyp = nilfs_btree_node_get_key(node, index);
    if (ptrp != NULL)
        *ptrp = ptr;

    return 0;
}

static int nilfs_btree_lookup(const struct nilfs_bmap *btree,
                  __u64 key, int level, __u64 *ptrp)
{
    struct nilfs_btree_path *path;
    int ret;

    path = nilfs_btree_alloc_path();
    if (path == NULL)
        return -ENOMEM;

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

    nilfs_btree_free_path(path);

    return ret;
}

static int nilfs_btree_lookup_contig(const struct nilfs_bmap *btree,
                     __u64 key, __u64 *ptrp, unsigned maxblocks)
{
    struct nilfs_btree_path *path;
    struct nilfs_btree_node *node;
    struct inode *dat = NULL;
    __u64 ptr, ptr2;
    sector_t blocknr;
    int level = NILFS_BTREE_LEVEL_NODE_MIN;
    int ret, cnt, index, maxlevel, ncmax;
    struct nilfs_btree_readahead_info p;

    path = nilfs_btree_alloc_path();
    if (path == NULL)
        return -ENOMEM;

    ret = nilfs_btree_do_lookup(btree, path, key, &ptr, level, 1);
    if (ret < 0)
        goto out;

    if (NILFS_BMAP_USE_VBN(btree)) {
        dat = nilfs_bmap_get_dat(btree);
        ret = nilfs_dat_translate(dat, ptr, &blocknr);
        if (ret < 0)
            goto out;
        ptr = blocknr;
    }
    cnt = 1;
    if (cnt == maxblocks)
        goto end;

    maxlevel = nilfs_btree_height(btree) - 1;
    node = nilfs_btree_get_node(btree, path, level, &ncmax);
    index = path[level].bp_index + 1;
    for (;;) {
        while (index < nilfs_btree_node_get_nchildren(node)) {
            if (nilfs_btree_node_get_key(node, index) !=
                key + cnt)
                goto end;
            ptr2 = nilfs_btree_node_get_ptr(node, index, ncmax);
            if (dat) {
                ret = nilfs_dat_translate(dat, ptr2, &blocknr);
                if (ret < 0)
                    goto out;
                ptr2 = blocknr;
            }
            if (ptr2 != ptr + cnt || ++cnt == maxblocks)
                goto end;
            index++;
            continue;
        }
        if (level == maxlevel)
            break;

        /* look-up right sibling node */
        p.node = nilfs_btree_get_node(btree, path, level + 1, &p.ncmax);
        p.index = path[level + 1].bp_index + 1;
        p.max_ra_blocks = 7;
        if (p.index >= nilfs_btree_node_get_nchildren(p.node) ||
            nilfs_btree_node_get_key(p.node, p.index) != key + cnt)
            break;
        ptr2 = nilfs_btree_node_get_ptr(p.node, p.index, p.ncmax);
        path[level + 1].bp_index = p.index;

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

        ret = __nilfs_btree_get_block(btree, ptr2, &path[level].bp_bh,
                          &p);
        if (ret < 0)
            goto out;
        node = nilfs_btree_get_nonroot_node(path, level);
        ncmax = nilfs_btree_nchildren_per_block(btree);
        index = 0;
        path[level].bp_index = index;
    }
 end:
    *ptrp = ptr;
    ret = cnt;
 out:
    nilfs_btree_free_path(path);
    return ret;
}

static void nilfs_btree_promote_key(struct nilfs_bmap *btree,
                    struct nilfs_btree_path *path,
                    int level, __u64 key)
{
    if (level < nilfs_btree_height(btree) - 1) {
        do {
            nilfs_btree_node_set_key(
                nilfs_btree_get_nonroot_node(path, level),
                path[level].bp_index, key);
            if (!buffer_dirty(path[level].bp_bh))
                mark_buffer_dirty(path[level].bp_bh);
        } while ((path[level].bp_index == 0) &&
             (++level < nilfs_btree_height(btree) - 1));
    }

    /* root */
    if (level == nilfs_btree_height(btree) - 1) {
        nilfs_btree_node_set_key(nilfs_btree_get_root(btree),
                     path[level].bp_index, key);
    }
}

static void nilfs_btree_do_insert(struct nilfs_bmap *btree,
                  struct nilfs_btree_path *path,
                  int level, __u64 *keyp, __u64 *ptrp)
{
    struct nilfs_btree_node *node;
    int ncblk;

    if (level < nilfs_btree_height(btree) - 1) {
        node = nilfs_btree_get_nonroot_node(path, level);
        ncblk = nilfs_btree_nchildren_per_block(btree);
        nilfs_btree_node_insert(node, path[level].bp_index,
                    *keyp, *ptrp, ncblk);
        if (!buffer_dirty(path[level].bp_bh))
            mark_buffer_dirty(path[level].bp_bh);

        if (path[level].bp_index == 0)
            nilfs_btree_promote_key(btree, path, level + 1,
                        nilfs_btree_node_get_key(node,
                                     0));
    } else {
        node = nilfs_btree_get_root(btree);
        nilfs_btree_node_insert(node, path[level].bp_index,
                    *keyp, *ptrp,
                    NILFS_BTREE_ROOT_NCHILDREN_MAX);
    }
}

static void nilfs_btree_carry_left(struct nilfs_bmap *btree,
                   struct nilfs_btree_path *path,
                   int level, __u64 *keyp, __u64 *ptrp)
{
    struct nilfs_btree_node *node, *left;
    int nchildren, lnchildren, n, move, ncblk;

    node = nilfs_btree_get_nonroot_node(path, level);
    left = nilfs_btree_get_sib_node(path, level);
    nchildren = nilfs_btree_node_get_nchildren(node);
    lnchildren = nilfs_btree_node_get_nchildren(left);
    ncblk = nilfs_btree_nchildren_per_block(btree);
    move = 0;

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

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

    if (!buffer_dirty(path[level].bp_bh))
        mark_buffer_dirty(path[level].bp_bh);
    if (!buffer_dirty(path[level].bp_sib_bh))
        mark_buffer_dirty(path[level].bp_sib_bh);

    nilfs_btree_promote_key(btree, path, level + 1,
                nilfs_btree_node_get_key(node, 0));

    if (move) {
        brelse(path[level].bp_bh);
        path[level].bp_bh = path[level].bp_sib_bh;
        path[level].bp_sib_bh = NULL;
        path[level].bp_index += lnchildren;
        path[level + 1].bp_index--;
    } else {
        brelse(path[level].bp_sib_bh);
        path[level].bp_sib_bh = NULL;
        path[level].bp_index -= n;
    }

    nilfs_btree_do_insert(btree, path, level, keyp, ptrp);
}

static void nilfs_btree_carry_right(struct nilfs_bmap *btree,
                    struct nilfs_btree_path *path,
                    int level, __u64 *keyp, __u64 *ptrp)
{
    struct nilfs_btree_node *node, *right;
    int nchildren, rnchildren, n, move, ncblk;

    node = nilfs_btree_get_nonroot_node(path, level);
    right = nilfs_btree_get_sib_node(path, level);
    nchildren = nilfs_btree_node_get_nchildren(node);
    rnchildren = nilfs_btree_node_get_nchildren(right);
    ncblk = nilfs_btree_nchildren_per_block(btree);
    move = 0;

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

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

    if (!buffer_dirty(path[level].bp_bh))
        mark_buffer_dirty(path[level].bp_bh);
    if (!buffer_dirty(path[level].bp_sib_bh))
        mark_buffer_dirty(path[level].bp_sib_bh);

    path[level + 1].bp_index++;
    nilfs_btree_promote_key(btree, path, level + 1,
                nilfs_btree_node_get_key(right, 0));
    path[level + 1].bp_index--;

    if (move) {
        brelse(path[level].bp_bh);
        path[level].bp_bh = path[level].bp_sib_bh;
        path[level].bp_sib_bh = NULL;
        path[level].bp_index -= nilfs_btree_node_get_nchildren(node);
        path[level + 1].bp_index++;
    } else {
        brelse(path[level].bp_sib_bh);
        path[level].bp_sib_bh = NULL;
    }

    nilfs_btree_do_insert(btree, path, level, keyp, ptrp);
}

static void nilfs_btree_split(struct nilfs_bmap *btree,
                  struct nilfs_btree_path *path,
                  int level, __u64 *keyp, __u64 *ptrp)
{
    struct nilfs_btree_node *node, *right;
    __u64 newkey;
    __u64 newptr;
    int nchildren, n, move, ncblk;

    node = nilfs_btree_get_nonroot_node(path, level);
    right = nilfs_btree_get_sib_node(path, level);
    nchildren = nilfs_btree_node_get_nchildren(node);
    ncblk = nilfs_btree_nchildren_per_block(btree);
    move = 0;

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

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

    if (!buffer_dirty(path[level].bp_bh))
        mark_buffer_dirty(path[level].bp_bh);
    if (!buffer_dirty(path[level].bp_sib_bh))
        mark_buffer_dirty(path[level].bp_sib_bh);

    newkey = nilfs_btree_node_get_key(right, 0);
    newptr = path[level].bp_newreq.bpr_ptr;

    if (move) {
        path[level].bp_index -= nilfs_btree_node_get_nchildren(node);
        nilfs_btree_node_insert(right, path[level].bp_index,
                    *keyp, *ptrp, ncblk);

        *keyp = nilfs_btree_node_get_key(right, 0);
        *ptrp = path[level].bp_newreq.bpr_ptr;

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

        *keyp = nilfs_btree_node_get_key(right, 0);
        *ptrp = path[level].bp_newreq.bpr_ptr;

        brelse(path[level].bp_sib_bh);
        path[level].bp_sib_bh = NULL;
    }

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

static void nilfs_btree_grow(struct nilfs_bmap *btree,
                 struct nilfs_btree_path *path,
                 int level, __u64 *keyp, __u64 *ptrp)
{
    struct nilfs_btree_node *root, *child;
    int n, ncblk;

    root = nilfs_btree_get_root(btree);
    child = nilfs_btree_get_sib_node(path, level);
    ncblk = nilfs_btree_nchildren_per_block(btree);

    n = nilfs_btree_node_get_nchildren(root);

    nilfs_btree_node_move_right(root, child, n,
                    NILFS_BTREE_ROOT_NCHILDREN_MAX, ncblk);
    nilfs_btree_node_set_level(root, level + 1);

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

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

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

    *keyp = nilfs_btree_node_get_key(child, 0);
    *ptrp = path[level].bp_newreq.bpr_ptr;
}

static __u64 nilfs_btree_find_near(const struct nilfs_bmap *btree,
                   const struct nilfs_btree_path *path)
{
    struct nilfs_btree_node *node;
    int level, ncmax;

    if (path == NULL)
        return NILFS_BMAP_INVALID_PTR;

    /* left sibling */
    level = NILFS_BTREE_LEVEL_NODE_MIN;
    if (path[level].bp_index > 0) {
        node = nilfs_btree_get_node(btree, path, level, &ncmax);
        return nilfs_btree_node_get_ptr(node,
                        path[level].bp_index - 1,
                        ncmax);
    }

    /* parent */
    level = NILFS_BTREE_LEVEL_NODE_MIN + 1;
    if (level <= nilfs_btree_height(btree) - 1) {
        node = nilfs_btree_get_node(btree, path, level, &ncmax);
        return nilfs_btree_node_get_ptr(node, path[level].bp_index,
                        ncmax);
    }

    return NILFS_BMAP_INVALID_PTR;
}

static __u64 nilfs_btree_find_target_v(const struct nilfs_bmap *btree,
                       const struct nilfs_btree_path *path,
                       __u64 key)
{
    __u64 ptr;

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

static int nilfs_btree_prepare_insert(struct nilfs_bmap *btree,
                      struct nilfs_btree_path *path,
                      int *levelp, __u64 key, __u64 ptr,
                      struct nilfs_bmap_stats *stats)
{
    struct buffer_head *bh;
    struct nilfs_btree_node *node, *parent, *sib;
    __u64 sibptr;
    int pindex, level, ncmax, ncblk, ret;
    struct inode *dat = NULL;

    stats->bs_nblocks = 0;
    level = NILFS_BTREE_LEVEL_DATA;

    /* allocate a new ptr for data block */
    if (NILFS_BMAP_USE_VBN(btree)) {
        path[level].bp_newreq.bpr_ptr =
            nilfs_btree_find_target_v(btree, path, key);
        dat = nilfs_bmap_get_dat(btree);
    }

    ret = nilfs_bmap_prepare_alloc_ptr(btree, &path[level].bp_newreq, dat);
    if (ret < 0)
        goto err_out_data;

    ncblk = nilfs_btree_nchildren_per_block(btree);

    for (level = NILFS_BTREE_LEVEL_NODE_MIN;
         level < nilfs_btree_height(btree) - 1;
         level++) {
        node = nilfs_btree_get_nonroot_node(path, level);
        if (nilfs_btree_node_get_nchildren(node) < ncblk) {
            path[level].bp_op = nilfs_btree_do_insert;
            stats->bs_nblocks++;
            goto out;
        }

        parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
        pindex = path[level + 1].bp_index;

        /* left sibling */
        if (pindex > 0) {
            sibptr = nilfs_btree_node_get_ptr(parent, pindex - 1,
                              ncmax);
            ret = nilfs_btree_get_block(btree, sibptr, &bh);
            if (ret < 0)
                goto err_out_child_node;
            sib = (struct nilfs_btree_node *)bh->b_data;
            if (nilfs_btree_node_get_nchildren(sib) < ncblk) {
                path[level].bp_sib_bh = bh;
                path[level].bp_op = nilfs_btree_carry_left;
                stats->bs_nblocks++;
                goto out;
            } else {
                brelse(bh);
            }
        }

        /* right sibling */
        if (pindex < nilfs_btree_node_get_nchildren(parent) - 1) {
            sibptr = nilfs_btree_node_get_ptr(parent, pindex + 1,
                              ncmax);
            ret = nilfs_btree_get_block(btree, sibptr, &bh);
            if (ret < 0)
                goto err_out_child_node;
            sib = (struct nilfs_btree_node *)bh->b_data;
            if (nilfs_btree_node_get_nchildren(sib) < ncblk) {
                path[level].bp_sib_bh = bh;
                path[level].bp_op = nilfs_btree_carry_right;
                stats->bs_nblocks++;
                goto out;
            } else {
                brelse(bh);
            }
        }

        /* split */
        path[level].bp_newreq.bpr_ptr =
            path[level - 1].bp_newreq.bpr_ptr + 1;
        ret = nilfs_bmap_prepare_alloc_ptr(btree,
                           &path[level].bp_newreq, dat);
        if (ret < 0)
            goto err_out_child_node;
        ret = nilfs_btree_get_new_block(btree,
                        path[level].bp_newreq.bpr_ptr,
                        &bh);
        if (ret < 0)
            goto err_out_curr_node;

        stats->bs_nblocks++;

        sib = (struct nilfs_btree_node *)bh->b_data;
        nilfs_btree_node_init(sib, 0, level, 0, ncblk, NULL, NULL);
        path[level].bp_sib_bh = bh;
        path[level].bp_op = nilfs_btree_split;
    }

    /* root */
    node = nilfs_btree_get_root(btree);
    if (nilfs_btree_node_get_nchildren(node) <
        NILFS_BTREE_ROOT_NCHILDREN_MAX) {
        path[level].bp_op = nilfs_btree_do_insert;
        stats->bs_nblocks++;
        goto out;
    }

    /* grow */
    path[level].bp_newreq.bpr_ptr = path[level - 1].bp_newreq.bpr_ptr + 1;
    ret = nilfs_bmap_prepare_alloc_ptr(btree, &path[level].bp_newreq, dat);
    if (ret < 0)
        goto err_out_child_node;
    ret = nilfs_btree_get_new_block(btree, path[level].bp_newreq.bpr_ptr,
                    &bh);
    if (ret < 0)
        goto err_out_curr_node;

    nilfs_btree_node_init((struct nilfs_btree_node *)bh->b_data,
                  0, level, 0, ncblk, NULL, NULL);
    path[level].bp_sib_bh = bh;
    path[level].bp_op = nilfs_btree_grow;

    level++;
    path[level].bp_op = nilfs_btree_do_insert;

    /* a newly-created node block and a data block are added */
    stats->bs_nblocks += 2;

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

    /* error */
 err_out_curr_node:
    nilfs_bmap_abort_alloc_ptr(btree, &path[level].bp_newreq, dat);
 err_out_child_node:
    for (level--; level > NILFS_BTREE_LEVEL_DATA; level--) {
        nilfs_btnode_delete(path[level].bp_sib_bh);
        nilfs_bmap_abort_alloc_ptr(btree, &path[level].bp_newreq, dat);

    }

    nilfs_bmap_abort_alloc_ptr(btree, &path[level].bp_newreq, dat);
 err_out_data:
    *levelp = level;
    stats->bs_nblocks = 0;
    return ret;
}

static void nilfs_btree_commit_insert(struct nilfs_bmap *btree,
                      struct nilfs_btree_path *path,
                      int maxlevel, __u64 key, __u64 ptr)
{
    struct inode *dat = NULL;
    int level;

    set_buffer_nilfs_volatile((struct buffer_head *)((unsigned long)ptr));
    ptr = path[NILFS_BTREE_LEVEL_DATA].bp_newreq.bpr_ptr;
    if (NILFS_BMAP_USE_VBN(btree)) {
        nilfs_bmap_set_target_v(btree, key, ptr);
        dat = nilfs_bmap_get_dat(btree);
    }

    for (level = NILFS_BTREE_LEVEL_NODE_MIN; level <= maxlevel; level++) {
        nilfs_bmap_commit_alloc_ptr(btree,
                        &path[level - 1].bp_newreq, dat);
        path[level].bp_op(btree, path, level, &key, &ptr);
    }

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

static int nilfs_btree_insert(struct nilfs_bmap *btree, __u64 key, __u64 ptr)
{
    struct nilfs_btree_path *path;
    struct nilfs_bmap_stats stats;
    int level, ret;

    path = nilfs_btree_alloc_path();
    if (path == NULL)
        return -ENOMEM;

    ret = nilfs_btree_do_lookup(btree, path, key, NULL,
                    NILFS_BTREE_LEVEL_NODE_MIN, 0);
    if (ret != -ENOENT) {
        if (ret == 0)
            ret = -EEXIST;
        goto out;
    }

    ret = nilfs_btree_prepare_insert(btree, path, &level, key, ptr, &stats);
    if (ret < 0)
        goto out;
    nilfs_btree_commit_insert(btree, path, level, key, ptr);
    nilfs_inode_add_blocks(btree->b_inode, stats.bs_nblocks);

 out:
    nilfs_btree_free_path(path);
    return ret;
}

static void nilfs_btree_do_delete(struct nilfs_bmap *btree,
                  struct nilfs_btree_path *path,
                  int level, __u64 *keyp, __u64 *ptrp)
{
    struct nilfs_btree_node *node;
    int ncblk;

    if (level < nilfs_btree_height(btree) - 1) {
        node = nilfs_btree_get_nonroot_node(path, level);
        ncblk = nilfs_btree_nchildren_per_block(btree);
        nilfs_btree_node_delete(node, path[level].bp_index,
                    keyp, ptrp, ncblk);
        if (!buffer_dirty(path[level].bp_bh))
            mark_buffer_dirty(path[level].bp_bh);
        if (path[level].bp_index == 0)
            nilfs_btree_promote_key(btree, path, level + 1,
                nilfs_btree_node_get_key(node, 0));
    } else {
        node = nilfs_btree_get_root(btree);
        nilfs_btree_node_delete(node, path[level].bp_index,
                    keyp, ptrp,
                    NILFS_BTREE_ROOT_NCHILDREN_MAX);
    }
}

static void nilfs_btree_borrow_left(struct nilfs_bmap *btree,
                    struct nilfs_btree_path *path,
                    int level, __u64 *keyp, __u64 *ptrp)
{
    struct nilfs_btree_node *node, *left;
    int nchildren, lnchildren, n, ncblk;

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

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

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

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

    if (!buffer_dirty(path[level].bp_bh))
        mark_buffer_dirty(path[level].bp_bh);
    if (!buffer_dirty(path[level].bp_sib_bh))
        mark_buffer_dirty(path[level].bp_sib_bh);

    nilfs_btree_promote_key(btree, path, level + 1,
                nilfs_btree_node_get_key(node, 0));

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

static void nilfs_btree_borrow_right(struct nilfs_bmap *btree,
                     struct nilfs_btree_path *path,
                     int level, __u64 *keyp, __u64 *ptrp)
{
    struct nilfs_btree_node *node, *right;
    int nchildren, rnchildren, n, ncblk;

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

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

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

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

    if (!buffer_dirty(path[level].bp_bh))
        mark_buffer_dirty(path[level].bp_bh);
    if (!buffer_dirty(path[level].bp_sib_bh))
        mark_buffer_dirty(path[level].bp_sib_bh);

    path[level + 1].bp_index++;
    nilfs_btree_promote_key(btree, path, level + 1,
                nilfs_btree_node_get_key(right, 0));
    path[level + 1].bp_index--;

    brelse(path[level].bp_sib_bh);
    path[level].bp_sib_bh = NULL;
}

static void nilfs_btree_concat_left(struct nilfs_bmap *btree,
                    struct nilfs_btree_path *path,
                    int level, __u64 *keyp, __u64 *ptrp)
{
    struct nilfs_btree_node *node, *left;
    int n, ncblk;

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

    node = nilfs_btree_get_nonroot_node(path, level);
    left = nilfs_btree_get_sib_node(path, level);
    ncblk = nilfs_btree_nchildren_per_block(btree);

    n = nilfs_btree_node_get_nchildren(node);

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

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

    nilfs_btnode_delete(path[level].bp_bh);
    path[level].bp_bh = path[level].bp_sib_bh;
    path[level].bp_sib_bh = NULL;
    path[level].bp_index += nilfs_btree_node_get_nchildren(left);
}

static void nilfs_btree_concat_right(struct nilfs_bmap *btree,
                     struct nilfs_btree_path *path,
                     int level, __u64 *keyp, __u64 *ptrp)
{
    struct nilfs_btree_node *node, *right;
    int n, ncblk;

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

    node = nilfs_btree_get_nonroot_node(path, level);
    right = nilfs_btree_get_sib_node(path, level);
    ncblk = nilfs_btree_nchildren_per_block(btree);

    n = nilfs_btree_node_get_nchildren(right);

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

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

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

static void nilfs_btree_shrink(struct nilfs_bmap *btree,
                   struct nilfs_btree_path *path,
                   int level, __u64 *keyp, __u64 *ptrp)
{
    struct nilfs_btree_node *root, *child;
    int n, ncblk;

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

    root = nilfs_btree_get_root(btree);
    child = nilfs_btree_get_nonroot_node(path, level);
    ncblk = nilfs_btree_nchildren_per_block(btree);

    nilfs_btree_node_delete(root, 0, NULL, NULL,
                NILFS_BTREE_ROOT_NCHILDREN_MAX);
    nilfs_btree_node_set_level(root, level);
    n = nilfs_btree_node_get_nchildren(child);
    nilfs_btree_node_move_left(root, child, n,
                   NILFS_BTREE_ROOT_NCHILDREN_MAX, ncblk);

    nilfs_btnode_delete(path[level].bp_bh);
    path[level].bp_bh = NULL;
}

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

static int nilfs_btree_prepare_delete(struct nilfs_bmap *btree,
                      struct nilfs_btree_path *path,
                      int *levelp,
                      struct nilfs_bmap_stats *stats,
                      struct inode *dat)
{
    struct buffer_head *bh;
    struct nilfs_btree_node *node, *parent, *sib;
    __u64 sibptr;
    int pindex, dindex, level, ncmin, ncmax, ncblk, ret;

    ret = 0;
    stats->bs_nblocks = 0;
    ncmin = NILFS_BTREE_NODE_NCHILDREN_MIN(nilfs_btree_node_size(btree));
    ncblk = nilfs_btree_nchildren_per_block(btree);

    for (level = NILFS_BTREE_LEVEL_NODE_MIN, dindex = path[level].bp_index;
         level < nilfs_btree_height(btree) - 1;
         level++) {
        node = nilfs_btree_get_nonroot_node(path, level);
        path[level].bp_oldreq.bpr_ptr =
            nilfs_btree_node_get_ptr(node, dindex, ncblk);
        ret = nilfs_bmap_prepare_end_ptr(btree,
                         &path[level].bp_oldreq, dat);
        if (ret < 0)
            goto err_out_child_node;

        if (nilfs_btree_node_get_nchildren(node) > ncmin) {
            path[level].bp_op = nilfs_btree_do_delete;
            stats->bs_nblocks++;
            goto out;
        }

        parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
        pindex = path[level + 1].bp_index;
        dindex = pindex;

        if (pindex > 0) {
            /* left sibling */
            sibptr = nilfs_btree_node_get_ptr(parent, pindex - 1,
                              ncmax);
            ret = nilfs_btree_get_block(btree, sibptr, &bh);
            if (ret < 0)
                goto err_out_curr_node;
            sib = (struct nilfs_btree_node *)bh->b_data;
            if (nilfs_btree_node_get_nchildren(sib) > ncmin) {
                path[level].bp_sib_bh = bh;
                path[level].bp_op = nilfs_btree_borrow_left;
                stats->bs_nblocks++;
                goto out;
            } else {
                path[level].bp_sib_bh = bh;
                path[level].bp_op = nilfs_btree_concat_left;
                stats->bs_nblocks++;
                /* continue; */
            }
        } else if (pindex <
               nilfs_btree_node_get_nchildren(parent) - 1) {
            /* right sibling */
            sibptr = nilfs_btree_node_get_ptr(parent, pindex + 1,
                              ncmax);
            ret = nilfs_btree_get_block(btree, sibptr, &bh);
            if (ret < 0)
                goto err_out_curr_node;
            sib = (struct nilfs_btree_node *)bh->b_data;
            if (nilfs_btree_node_get_nchildren(sib) > ncmin) {
                path[level].bp_sib_bh = bh;
                path[level].bp_op = nilfs_btree_borrow_right;
                stats->bs_nblocks++;
                goto out;
            } else {
                path[level].bp_sib_bh = bh;
                path[level].bp_op = nilfs_btree_concat_right;
                stats->bs_nblocks++;
                /*
                 * When merging right sibling node
                 * into the current node, pointer to
                 * the right sibling node must be
                 * terminated instead.  The adjustment
                 * below is required for that.
                 */
                dindex = pindex + 1;
                /* continue; */
            }
        } else {
            /* no siblings */
            /* the only child of the root node */
            WARN_ON(level != nilfs_btree_height(btree) - 2);
            if (nilfs_btree_node_get_nchildren(node) - 1 <=
                NILFS_BTREE_ROOT_NCHILDREN_MAX) {
                path[level].bp_op = nilfs_btree_shrink;
                stats->bs_nblocks += 2;
                level++;
                path[level].bp_op = nilfs_btree_nop;
                goto shrink_root_child;
            } else {
                path[level].bp_op = nilfs_btree_do_delete;
                stats->bs_nblocks++;
                goto out;
            }
        }
    }

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

shrink_root_child:
    node = nilfs_btree_get_root(btree);
    path[level].bp_oldreq.bpr_ptr =
        nilfs_btree_node_get_ptr(node, dindex,
                     NILFS_BTREE_ROOT_NCHILDREN_MAX);

    ret = nilfs_bmap_prepare_end_ptr(btree, &path[level].bp_oldreq, dat);
    if (ret < 0)
        goto err_out_child_node;

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

    /* error */
 err_out_curr_node:
    nilfs_bmap_abort_end_ptr(btree, &path[level].bp_oldreq, dat);
 err_out_child_node:
    for (level--; level >= NILFS_BTREE_LEVEL_NODE_MIN; level--) {
        brelse(path[level].bp_sib_bh);
        nilfs_bmap_abort_end_ptr(btree, &path[level].bp_oldreq, dat);
    }
    *levelp = level;
    stats->bs_nblocks = 0;
    return ret;
}

static void nilfs_btree_commit_delete(struct nilfs_bmap *btree,
                      struct nilfs_btree_path *path,
                      int maxlevel, struct inode *dat)
{
    int level;

    for (level = NILFS_BTREE_LEVEL_NODE_MIN; level <= maxlevel; level++) {
        nilfs_bmap_commit_end_ptr(btree, &path[level].bp_oldreq, dat);
        path[level].bp_op(btree, path, level, NULL, NULL);
    }

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

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

{
    struct nilfs_btree_path *path;
    struct nilfs_bmap_stats stats;
    struct inode *dat;
    int level, ret;

    path = nilfs_btree_alloc_path();
    if (path == NULL)
        return -ENOMEM;

    ret = nilfs_btree_do_lookup(btree, path, key, NULL,
                    NILFS_BTREE_LEVEL_NODE_MIN, 0);
    if (ret < 0)
        goto out;


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

    ret = nilfs_btree_prepare_delete(btree, path, &level, &stats, dat);
    if (ret < 0)
        goto out;
    nilfs_btree_commit_delete(btree, path, level, dat);
    nilfs_inode_sub_blocks(btree->b_inode, stats.bs_nblocks);

out:
    nilfs_btree_free_path(path);
    return ret;
}

static int nilfs_btree_last_key(const struct nilfs_bmap *btree, __u64 *keyp)
{
    struct nilfs_btree_path *path;
    int ret;

    path = nilfs_btree_alloc_path();
    if (path == NULL)
        return -ENOMEM;

    ret = nilfs_btree_do_lookup_last(btree, path, keyp, NULL);

    nilfs_btree_free_path(path);

    return ret;
}

static int nilfs_btree_check_delete(struct nilfs_bmap *btree, __u64 key)
{
    struct buffer_head *bh;
    struct nilfs_btree_node *root, *node;
    __u64 maxkey, nextmaxkey;
    __u64 ptr;
    int nchildren, ret;

    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(root);
        if (nchildren > 1)
            return 0;
        ptr = nilfs_btree_node_get_ptr(root, nchildren - 1,
                           NILFS_BTREE_ROOT_NCHILDREN_MAX);
        ret = nilfs_btree_get_block(btree, 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(node);
    maxkey = nilfs_btree_node_get_key(node, nchildren - 1);
    nextmaxkey = (nchildren > 1) ?
        nilfs_btree_node_get_key(node, nchildren - 2) : 0;
    if (bh != NULL)
        brelse(bh);

    return (maxkey == key) && (nextmaxkey < NILFS_BMAP_LARGE_LOW);
}

static int nilfs_btree_gather_data(struct nilfs_bmap *btree,
                   __u64 *keys, __u64 *ptrs, int nitems)
{
    struct buffer_head *bh;
    struct nilfs_btree_node *node, *root;
    __le64 *dkeys;
    __le64 *dptrs;
    __u64 ptr;
    int nchildren, ncmax, i, ret;

    root = nilfs_btree_get_root(btree);
    switch (nilfs_btree_height(btree)) {
    case 2:
        bh = NULL;
        node = root;
        ncmax = NILFS_BTREE_ROOT_NCHILDREN_MAX;
        break;
    case 3:
        nchildren = nilfs_btree_node_get_nchildren(root);
        WARN_ON(nchildren > 1);
        ptr = nilfs_btree_node_get_ptr(root, nchildren - 1,
                           NILFS_BTREE_ROOT_NCHILDREN_MAX);
        ret = nilfs_btree_get_block(btree, ptr, &bh);
        if (ret < 0)
            return ret;
        node = (struct nilfs_btree_node *)bh->b_data;
        ncmax = nilfs_btree_nchildren_per_block(btree);
        break;
    default:
        node = NULL;
        return -EINVAL;
    }

    nchildren = nilfs_btree_node_get_nchildren(node);
    if (nchildren < nitems)
        nitems = nchildren;
    dkeys = nilfs_btree_node_dkeys(node);
    dptrs = nilfs_btree_node_dptrs(node, ncmax);
    for (i = 0; i < nitems; i++) {
        keys[i] = le64_to_cpu(dkeys[i]);
        ptrs[i] = le64_to_cpu(dptrs[i]);
    }

    if (bh != NULL)
        brelse(bh);

    return nitems;
}

static int
nilfs_btree_prepare_convert_and_insert(struct nilfs_bmap *btree, __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 inode *dat = NULL;
    int ret;

    stats->bs_nblocks = 0;

    /* for data */
    /* cannot find near ptr */
    if (NILFS_BMAP_USE_VBN(btree)) {
        dreq->bpr_ptr = nilfs_btree_find_target_v(btree, NULL, key);
        dat = nilfs_bmap_get_dat(btree);
    }

    ret = nilfs_bmap_prepare_alloc_ptr(btree, dreq, dat);
    if (ret < 0)
        return ret;

    *bhp = NULL;
    stats->bs_nblocks++;
    if (nreq != NULL) {
        nreq->bpr_ptr = dreq->bpr_ptr + 1;
        ret = nilfs_bmap_prepare_alloc_ptr(btree, nreq, dat);
        if (ret < 0)
            goto err_out_dreq;

        ret = nilfs_btree_get_new_block(btree, nreq->bpr_ptr, &bh);
        if (ret < 0)
            goto err_out_nreq;

        *bhp = bh;
        stats->bs_nblocks++;
    }

    /* success */
    return 0;

    /* error */
 err_out_nreq:
    nilfs_bmap_abort_alloc_ptr(btree, nreq, dat);
 err_out_dreq:
    nilfs_bmap_abort_alloc_ptr(btree, dreq, dat);
    stats->bs_nblocks = 0;
    return ret;

}

static void
nilfs_btree_commit_convert_and_insert(struct nilfs_bmap *btree,
                      __u64 key, __u64 ptr,
                      const __u64 *keys, const __u64 *ptrs,
                      int n,
                      union nilfs_bmap_ptr_req *dreq,
                      union nilfs_bmap_ptr_req *nreq,
                      struct buffer_head *bh)
{
    struct nilfs_btree_node *node;
    struct inode *dat;
    __u64 tmpptr;
    int ncblk;

    /* free resources */
    if (btree->b_ops->bop_clear != NULL)
        btree->b_ops->bop_clear(btree);

    /* ptr must be a pointer to a buffer head. */
    set_buffer_nilfs_volatile((struct buffer_head *)((unsigned long)ptr));

    /* convert and insert */
    dat = NILFS_BMAP_USE_VBN(btree) ? nilfs_bmap_get_dat(btree) : NULL;
    nilfs_btree_init(btree);
    if (nreq != NULL) {
        nilfs_bmap_commit_alloc_ptr(btree, dreq, dat);
        nilfs_bmap_commit_alloc_ptr(btree, nreq, dat);

        /* create child node at level 1 */
        node = (struct nilfs_btree_node *)bh->b_data;
        ncblk = nilfs_btree_nchildren_per_block(btree);
        nilfs_btree_node_init(node, 0, 1, n, ncblk, keys, ptrs);
        nilfs_btree_node_insert(node, n, key, dreq->bpr_ptr, ncblk);
        if (!buffer_dirty(bh))
            mark_buffer_dirty(bh);
        if (!nilfs_bmap_dirty(btree))
            nilfs_bmap_set_dirty(btree);

        brelse(bh);

        /* create root node at level 2 */
        node = nilfs_btree_get_root(btree);
        tmpptr = nreq->bpr_ptr;
        nilfs_btree_node_init(node, NILFS_BTREE_NODE_ROOT, 2, 1,
                      NILFS_BTREE_ROOT_NCHILDREN_MAX,
                      &keys[0], &tmpptr);
    } else {
        nilfs_bmap_commit_alloc_ptr(btree, dreq, dat);

        /* create root node at level 1 */
        node = nilfs_btree_get_root(btree);
        nilfs_btree_node_init(node, NILFS_BTREE_NODE_ROOT, 1, n,
                      NILFS_BTREE_ROOT_NCHILDREN_MAX,
                      keys, ptrs);
        nilfs_btree_node_insert(node, n, key, dreq->bpr_ptr,
                    NILFS_BTREE_ROOT_NCHILDREN_MAX);
        if (!nilfs_bmap_dirty(btree))
            nilfs_bmap_set_dirty(btree);
    }

    if (NILFS_BMAP_USE_VBN(btree))
        nilfs_bmap_set_target_v(btree, key, dreq->bpr_ptr);
}

int nilfs_btree_convert_and_insert(struct nilfs_bmap *btree,
                   __u64 key, __u64 ptr,
                   const __u64 *keys, const __u64 *ptrs, int n)
{
    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 << btree->b_inode->i_blkbits)) {
        di = &dreq;
        ni = &nreq;
    } else {
        di = NULL;
        ni = NULL;
        BUG();
    }

    ret = nilfs_btree_prepare_convert_and_insert(btree, key, di, ni, &bh,
                             &stats);
    if (ret < 0)
        return ret;
    nilfs_btree_commit_convert_and_insert(btree, key, ptr, keys, ptrs, n,
                          di, ni, bh);
    nilfs_inode_add_blocks(btree->b_inode, stats.bs_nblocks);
    return 0;
}

static int nilfs_btree_propagate_p(struct nilfs_bmap *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))
        mark_buffer_dirty(path[level].bp_bh);

    return 0;
}

static int nilfs_btree_prepare_update_v(struct nilfs_bmap *btree,
                    struct nilfs_btree_path *path,
                    int level, struct inode *dat)
{
    struct nilfs_btree_node *parent;
    int ncmax, ret;

    parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
    path[level].bp_oldreq.bpr_ptr =
        nilfs_btree_node_get_ptr(parent, path[level + 1].bp_index,
                     ncmax);
    path[level].bp_newreq.bpr_ptr = path[level].bp_oldreq.bpr_ptr + 1;
    ret = nilfs_dat_prepare_update(dat, &path[level].bp_oldreq.bpr_req,
                       &path[level].bp_newreq.bpr_req);
    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)->i_btnode_cache,
            &path[level].bp_ctxt);
        if (ret < 0) {
            nilfs_dat_abort_update(dat,
                           &path[level].bp_oldreq.bpr_req,
                           &path[level].bp_newreq.bpr_req);
            return ret;
        }
    }

    return 0;
}

static void nilfs_btree_commit_update_v(struct nilfs_bmap *btree,
                    struct nilfs_btree_path *path,
                    int level, struct inode *dat)
{
    struct nilfs_btree_node *parent;
    int ncmax;

    nilfs_dat_commit_update(dat, &path[level].bp_oldreq.bpr_req,
                &path[level].bp_newreq.bpr_req,
                btree->b_ptr_type == NILFS_BMAP_PTR_VS);

    if (buffer_nilfs_node(path[level].bp_bh)) {
        nilfs_btnode_commit_change_key(
            &NILFS_BMAP_I(btree)->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, &ncmax);
    nilfs_btree_node_set_ptr(parent, path[level + 1].bp_index,
                 path[level].bp_newreq.bpr_ptr, ncmax);
}

static void nilfs_btree_abort_update_v(struct nilfs_bmap *btree,
                       struct nilfs_btree_path *path,
                       int level, struct inode *dat)
{
    nilfs_dat_abort_update(dat, &path[level].bp_oldreq.bpr_req,
                   &path[level].bp_newreq.bpr_req);
    if (buffer_nilfs_node(path[level].bp_bh))
        nilfs_btnode_abort_change_key(
            &NILFS_BMAP_I(btree)->i_btnode_cache,
            &path[level].bp_ctxt);
}

static int nilfs_btree_prepare_propagate_v(struct nilfs_bmap *btree,
                       struct nilfs_btree_path *path,
                       int minlevel, int *maxlevelp,
                       struct inode *dat)
{
    int level, ret;

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

    /* success */
    *maxlevelp = level - 1;
    return 0;

    /* error */
 out:
    while (--level > minlevel)
        nilfs_btree_abort_update_v(btree, path, level, dat);
    if (!buffer_nilfs_volatile(path[level].bp_bh))
        nilfs_btree_abort_update_v(btree, path, level, dat);
    return ret;
}

static void nilfs_btree_commit_propagate_v(struct nilfs_bmap *btree,
                       struct nilfs_btree_path *path,
                       int minlevel, int maxlevel,
                       struct buffer_head *bh,
                       struct inode *dat)
{
    int level;

    if (!buffer_nilfs_volatile(path[minlevel].bp_bh))
        nilfs_btree_commit_update_v(btree, path, minlevel, dat);

    for (level = minlevel + 1; level <= maxlevel; level++)
        nilfs_btree_commit_update_v(btree, path, level, dat);
}

static int nilfs_btree_propagate_v(struct nilfs_bmap *btree,
                   struct nilfs_btree_path *path,
                   int level, struct buffer_head *bh)
{
    int maxlevel = 0, ret;
    struct nilfs_btree_node *parent;
    struct inode *dat = nilfs_bmap_get_dat(btree);
    __u64 ptr;
    int ncmax;

    get_bh(bh);
    path[level].bp_bh = bh;
    ret = nilfs_btree_prepare_propagate_v(btree, path, level, &maxlevel,
                          dat);
    if (ret < 0)
        goto out;

    if (buffer_nilfs_volatile(path[level].bp_bh)) {
        parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
        ptr = nilfs_btree_node_get_ptr(parent,
                           path[level + 1].bp_index,
                           ncmax);
        ret = nilfs_dat_mark_dirty(dat, ptr);
        if (ret < 0)
            goto out;
    }

    nilfs_btree_commit_propagate_v(btree, path, level, maxlevel, bh, dat);

 out:
    brelse(path[level].bp_bh);
    path[level].bp_bh = NULL;
    return ret;
}

static int nilfs_btree_propagate(struct nilfs_bmap *btree,
                 struct buffer_head *bh)
{
    struct nilfs_btree_path *path;
    struct nilfs_btree_node *node;
    __u64 key;
    int level, ret;

    WARN_ON(!buffer_dirty(bh));

    path = nilfs_btree_alloc_path();
    if (path == NULL)
        return -ENOMEM;

    if (buffer_nilfs_node(bh)) {
        node = (struct nilfs_btree_node *)bh->b_data;
        key = nilfs_btree_node_get_key(node, 0);
        level = nilfs_btree_node_get_level(node);
    } else {
        key = nilfs_bmap_data_get_key(btree, bh);
        level = NILFS_BTREE_LEVEL_DATA;
    }

    ret = nilfs_btree_do_lookup(btree, path, key, NULL, level + 1, 0);
    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 = NILFS_BMAP_USE_VBN(btree) ?
        nilfs_btree_propagate_v(btree, path, level, bh) :
        nilfs_btree_propagate_p(btree, path, level, bh);

 out:
    nilfs_btree_free_path(path);

    return ret;
}

static int nilfs_btree_propagate_gc(struct nilfs_bmap *btree,
                    struct buffer_head *bh)
{
    return nilfs_dat_mark_dirty(nilfs_bmap_get_dat(btree), bh->b_blocknr);
}

static void nilfs_btree_add_dirty_buffer(struct nilfs_bmap *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(node, 0);
    level = nilfs_btree_node_get_level(node);
    if (level < NILFS_BTREE_LEVEL_NODE_MIN ||
        level >= NILFS_BTREE_LEVEL_MAX) {
        dump_stack();
        printk(KERN_WARNING
               "%s: invalid btree level: %d (key=%llu, ino=%lu, "
               "blocknr=%llu)\n",
               __func__, level, (unsigned long long)key,
               NILFS_BMAP_I(btree)->vfs_inode.i_ino,
               (unsigned long long)bh->b_blocknr);
        return;
    }

    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(cnode, 0);
        if (key < ckey)
            break;
    }
    list_add_tail(&bh->b_assoc_buffers, head);
}

static void nilfs_btree_lookup_dirty_buffers(struct nilfs_bmap *btree,
                         struct list_head *listp)
{
    struct address_space *btcache = &NILFS_BMAP_I(btree)->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_tail(&lists[level], listp);
}

static int nilfs_btree_assign_p(struct nilfs_bmap *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 ncmax, ret;

    parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
    ptr = nilfs_btree_node_get_ptr(parent, path[level + 1].bp_index,
                       ncmax);
    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)->i_btnode_cache,
            &path[level].bp_ctxt);
        if (ret < 0)
            return ret;
        nilfs_btnode_commit_change_key(
            &NILFS_BMAP_I(btree)->i_btnode_cache,
            &path[level].bp_ctxt);
        *bh = path[level].bp_ctxt.bh;
    }

    nilfs_btree_node_set_ptr(parent, path[level + 1].bp_index, blocknr,
                 ncmax);

    key = nilfs_btree_node_get_key(parent, path[level + 1].bp_index);
    /* on-disk format */
    binfo->bi_dat.bi_blkoff = cpu_to_le64(key);
    binfo->bi_dat.bi_level = level;

    return 0;
}

static int nilfs_btree_assign_v(struct nilfs_bmap *btree,
                struct nilfs_btree_path *path,
                int level,
                struct buffer_head **bh,
                sector_t blocknr,
                union nilfs_binfo *binfo)
{
    struct nilfs_btree_node *parent;
    struct inode *dat = nilfs_bmap_get_dat(btree);
    __u64 key;
    __u64 ptr;
    union nilfs_bmap_ptr_req req;
    int ncmax, ret;

    parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
    ptr = nilfs_btree_node_get_ptr(parent, path[level + 1].bp_index,
                       ncmax);
    req.bpr_ptr = ptr;
    ret = nilfs_dat_prepare_start(dat, &req.bpr_req);
    if (ret < 0)
        return ret;
    nilfs_dat_commit_start(dat, &req.bpr_req, blocknr);

    key = nilfs_btree_node_get_key(parent, path[level + 1].bp_index);
    /* on-disk format */
    binfo->bi_v.bi_vblocknr = cpu_to_le64(ptr);
    binfo->bi_v.bi_blkoff = cpu_to_le64(key);

    return 0;
}

static int nilfs_btree_assign(struct nilfs_bmap *btree,
                  struct buffer_head **bh,
                  sector_t blocknr,
                  union nilfs_binfo *binfo)
{
    struct nilfs_btree_path *path;
    struct nilfs_btree_node *node;
    __u64 key;
    int level, ret;

    path = nilfs_btree_alloc_path();
    if (path == NULL)
        return -ENOMEM;

    if (buffer_nilfs_node(*bh)) {
        node = (struct nilfs_btree_node *)(*bh)->b_data;
        key = nilfs_btree_node_get_key(node, 0);
        level = nilfs_btree_node_get_level(node);
    } else {
        key = nilfs_bmap_data_get_key(btree, *bh);
        level = NILFS_BTREE_LEVEL_DATA;
    }

    ret = nilfs_btree_do_lookup(btree, path, key, NULL, level + 1, 0);
    if (ret < 0) {
        WARN_ON(ret == -ENOENT);
        goto out;
    }

    ret = NILFS_BMAP_USE_VBN(btree) ?
        nilfs_btree_assign_v(btree, path, level, bh, blocknr, binfo) :
        nilfs_btree_assign_p(btree, path, level, bh, blocknr, binfo);

 out:
    nilfs_btree_free_path(path);

    return ret;
}

static int nilfs_btree_assign_gc(struct nilfs_bmap *btree,
                 struct buffer_head **bh,
                 sector_t blocknr,
                 union nilfs_binfo *binfo)
{
    struct nilfs_btree_node *node;
    __u64 key;
    int ret;

    ret = nilfs_dat_move(nilfs_bmap_get_dat(btree), (*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(node, 0);
    } else
        key = nilfs_bmap_data_get_key(btree, *bh);

    /* on-disk format */
    binfo->bi_v.bi_vblocknr = cpu_to_le64((*bh)->b_blocknr);
    binfo->bi_v.bi_blkoff = cpu_to_le64(key);

    return 0;
}

static int nilfs_btree_mark(struct nilfs_bmap *btree, __u64 key, int level)
{
    struct buffer_head *bh;
    struct nilfs_btree_path *path;
    __u64 ptr;
    int ret;

    path = nilfs_btree_alloc_path();
    if (path == NULL)
        return -ENOMEM;

    ret = nilfs_btree_do_lookup(btree, path, key, &ptr, level + 1, 0);
    if (ret < 0) {
        WARN_ON(ret == -ENOENT);
        goto out;
    }
    ret = nilfs_btree_get_block(btree, ptr, &bh);
    if (ret < 0) {
        WARN_ON(ret == -ENOENT);
        goto out;
    }

    if (!buffer_dirty(bh))
        mark_buffer_dirty(bh);
    brelse(bh);
    if (!nilfs_bmap_dirty(btree))
        nilfs_bmap_set_dirty(btree);

 out:
    nilfs_btree_free_path(path);
    return ret;
}

static const struct nilfs_bmap_operations nilfs_btree_ops = {
    .bop_lookup     =   nilfs_btree_lookup,
    .bop_lookup_contig  =   nilfs_btree_lookup_contig,
    .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_lookup_contig  =   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,
};

int nilfs_btree_init(struct nilfs_bmap *bmap)
{
    bmap->b_ops = &nilfs_btree_ops;
    bmap->b_nchildren_per_block =
        NILFS_BTREE_NODE_NCHILDREN_MAX(nilfs_btree_node_size(bmap));
    return 0;
}

void nilfs_btree_init_gc(struct nilfs_bmap *bmap)
{
    bmap->b_ops = &nilfs_btree_ops_gc;
    bmap->b_nchildren_per_block =
        NILFS_BTREE_NODE_NCHILDREN_MAX(nilfs_btree_node_size(bmap));
}