1 files changed, 524 insertions, 481 deletions

diff --git a/fs/nilfs2/btree.c b/fs/nilfs2/btree.c
index 76c38e3e19d2..300c2bc00c3f 100644
--- a/fs/nilfs2/btree.c
+++ b/fs/nilfs2/btree.c
@@ -31,63 +31,16 @@
 #include "alloc.h"
 #include "dat.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(void)
-{
-        return kmem_cache_alloc(nilfs_btree_path_cache, GFP_NOFS);
-}
-
-static inline void nilfs_btree_free_path(struct nilfs_btree_path *path)
+static struct nilfs_btree_path *nilfs_btree_alloc_path(void)
 {
-        kmem_cache_free(nilfs_btree_path_cache, path);
-}
+        struct nilfs_btree_path *path;
+        int level = NILFS_BTREE_LEVEL_DATA;
 
-static void nilfs_btree_init_path(struct nilfs_btree_path *path)
-{
-        int level;
+        path = kmem_cache_alloc(nilfs_btree_path_cache, GFP_NOFS);
+        if (path == NULL)
+                goto out;
 
-        for (level = NILFS_BTREE_LEVEL_DATA;
-             level < NILFS_BTREE_LEVEL_MAX;
-             level++) {
+        for (; level < NILFS_BTREE_LEVEL_MAX; level++) {
                 path[level].bp_bh = NULL;
                 path[level].bp_sib_bh = NULL;
                 path[level].bp_index = 0;
@@ -95,44 +48,28 @@ static void nilfs_btree_init_path(struct nilfs_btree_path *path)
                 path[level].bp_newreq.bpr_ptr = NILFS_BMAP_INVALID_PTR;
                 path[level].bp_op = NULL;
         }
+
+out:
+        return path;
 }
 
-static void nilfs_btree_release_path(struct nilfs_btree_path *path)
+static void nilfs_btree_free_path(struct nilfs_btree_path *path)
 {
-        int level;
+        int level = NILFS_BTREE_LEVEL_DATA;
 
-        for (level = NILFS_BTREE_LEVEL_DATA; level < NILFS_BTREE_LEVEL_MAX;
-             level++)
+        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_block(const struct nilfs_btree *btree, __u64 ptr,
-                                 struct buffer_head **bhp)
-{
-        struct address_space *btnc =
-                &NILFS_BMAP_I((struct nilfs_bmap *)btree)->i_btnode_cache;
-        int err;
-
-        err = nilfs_btnode_submit_block(btnc, ptr, 0, bhp);
-        if (err)
-                return err == -EEXIST ? 0 : err;
-
-        wait_on_buffer(*bhp);
-        if (!buffer_uptodate(*bhp)) {
-                brelse(*bhp);
-                return -EIO;
-        }
-        return 0;
-}
-
-static int nilfs_btree_get_new_block(const struct nilfs_btree *btree,
+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((struct nilfs_bmap *)btree)->i_btnode_cache;
+        struct address_space *btnc = &NILFS_BMAP_I(btree)->i_btnode_cache;
         struct buffer_head *bh;
 
         bh = nilfs_btnode_create_block(btnc, ptr);
@@ -144,71 +81,55 @@ static int nilfs_btree_get_new_block(const struct nilfs_btree *btree,
         return 0;
 }
 
-static inline int
-nilfs_btree_node_get_flags(const struct nilfs_btree_node *node)
+static int nilfs_btree_node_get_flags(const struct nilfs_btree_node *node)
 {
         return node->bn_flags;
 }
 
-static inline void
+static void
 nilfs_btree_node_set_flags(struct nilfs_btree_node *node, int flags)
 {
         node->bn_flags = flags;
 }
 
-static inline int nilfs_btree_node_root(const struct nilfs_btree_node *node)
+static int nilfs_btree_node_root(const struct nilfs_btree_node *node)
 {
         return nilfs_btree_node_get_flags(node) & NILFS_BTREE_NODE_ROOT;
 }
 
-static inline int
-nilfs_btree_node_get_level(const struct nilfs_btree_node *node)
+static int nilfs_btree_node_get_level(const struct nilfs_btree_node *node)
 {
         return node->bn_level;
 }
 
-static inline void
+static void
 nilfs_btree_node_set_level(struct nilfs_btree_node *node, int level)
 {
         node->bn_level = level;
 }
 
-static inline int
-nilfs_btree_node_get_nchildren(const struct nilfs_btree_node *node)
+static int nilfs_btree_node_get_nchildren(const struct nilfs_btree_node *node)
 {
         return le16_to_cpu(node->bn_nchildren);
 }
 
-static inline void
+static void
 nilfs_btree_node_set_nchildren(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_node *node,
-                               const struct nilfs_btree *btree)
+static int nilfs_btree_node_size(const struct nilfs_bmap *btree)
 {
-        return nilfs_btree_node_root(node) ?
-                NILFS_BTREE_ROOT_NCHILDREN_MIN :
-                NILFS_BTREE_NODE_NCHILDREN_MIN(nilfs_btree_node_size(btree));
+        return 1 << btree->b_inode->i_blkbits;
 }
 
-static inline int
-nilfs_btree_node_nchildren_max(const struct nilfs_btree_node *node,
-                               const struct nilfs_btree *btree)
+static int nilfs_btree_nchildren_per_block(const struct nilfs_bmap *btree)
 {
-        return nilfs_btree_node_root(node) ?
-                NILFS_BTREE_ROOT_NCHILDREN_MAX :
-                NILFS_BTREE_NODE_NCHILDREN_MAX(nilfs_btree_node_size(btree));
+        return btree->b_nchildren_per_block;
 }
 
-static inline __le64 *
+static __le64 *
 nilfs_btree_node_dkeys(const struct nilfs_btree_node *node)
 {
         return (__le64 *)((char *)(node + 1) +
@@ -216,45 +137,40 @@ nilfs_btree_node_dkeys(const struct nilfs_btree_node *node)
                            0 : NILFS_BTREE_NODE_EXTRA_PAD_SIZE));
 }
 
-static inline __le64 *
-nilfs_btree_node_dptrs(const struct nilfs_btree_node *node,
-                       const struct nilfs_btree *btree)
+static __le64 *
+nilfs_btree_node_dptrs(const struct nilfs_btree_node *node, int ncmax)
 {
-        return (__le64 *)(nilfs_btree_node_dkeys(node) +
-                          nilfs_btree_node_nchildren_max(node, btree));
+        return (__le64 *)(nilfs_btree_node_dkeys(node) + ncmax);
 }
 
-static inline __u64
+static __u64
 nilfs_btree_node_get_key(const struct nilfs_btree_node *node, int index)
 {
-        return nilfs_bmap_dkey_to_key(*(nilfs_btree_node_dkeys(node) + index));
+        return le64_to_cpu(*(nilfs_btree_node_dkeys(node) + index));
 }
 
-static inline void
+static void
 nilfs_btree_node_set_key(struct nilfs_btree_node *node, int index, __u64 key)
 {
-        *(nilfs_btree_node_dkeys(node) + index) = nilfs_bmap_key_to_dkey(key);
+        *(nilfs_btree_node_dkeys(node) + index) = cpu_to_le64(key);
 }
 
-static inline __u64
-nilfs_btree_node_get_ptr(const struct nilfs_btree *btree,
-                         const struct nilfs_btree_node *node, int index)
+static __u64
+nilfs_btree_node_get_ptr(const struct nilfs_btree_node *node, int index,
+                         int ncmax)
 {
-        return nilfs_bmap_dptr_to_ptr(*(nilfs_btree_node_dptrs(node, btree) +
-                                        index));
+        return le64_to_cpu(*(nilfs_btree_node_dptrs(node, ncmax) + index));
 }
 
-static inline void
-nilfs_btree_node_set_ptr(struct nilfs_btree *btree,
-                         struct nilfs_btree_node *node, int index, __u64 ptr)
+static void
+nilfs_btree_node_set_ptr(struct nilfs_btree_node *node, int index, __u64 ptr,
+                         int ncmax)
 {
-        *(nilfs_btree_node_dptrs(node, btree) + index) =
-                nilfs_bmap_ptr_to_dptr(ptr);
+        *(nilfs_btree_node_dptrs(node, ncmax) + index) = cpu_to_le64(ptr);
 }
 
-static void nilfs_btree_node_init(struct nilfs_btree *btree,
-                                  struct nilfs_btree_node *node,
-                                  int flags, int level, int nchildren,
+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;
@@ -266,29 +182,28 @@ static void nilfs_btree_node_init(struct nilfs_btree *btree,
         nilfs_btree_node_set_nchildren(node, nchildren);
 
         dkeys = nilfs_btree_node_dkeys(node);
-        dptrs = nilfs_btree_node_dptrs(node, btree);
+        dptrs = nilfs_btree_node_dptrs(node, ncmax);
         for (i = 0; i < nchildren; i++) {
-                dkeys[i] = nilfs_bmap_key_to_dkey(keys[i]);
-                dptrs[i] = nilfs_bmap_ptr_to_dptr(ptrs[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 *btree,
-                                       struct nilfs_btree_node *left,
+static void nilfs_btree_node_move_left(struct nilfs_btree_node *left,
                                        struct nilfs_btree_node *right,
-                                       int n)
+                                       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, btree);
+        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, btree);
+        rdptrs = nilfs_btree_node_dptrs(right, rncmax);
         rnchildren = nilfs_btree_node_get_nchildren(right);
 
         memcpy(ldkeys + lnchildren, rdkeys, n * sizeof(*rdkeys));
@@ -303,21 +218,20 @@ static void nilfs_btree_node_move_left(struct nilfs_btree *btree,
 }
 
 /* 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,
+static void nilfs_btree_node_move_right(struct nilfs_btree_node *left,
                                         struct nilfs_btree_node *right,
-                                        int n)
+                                        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, btree);
+        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, btree);
+        rdptrs = nilfs_btree_node_dptrs(right, rncmax);
         rnchildren = nilfs_btree_node_get_nchildren(right);
 
         memmove(rdkeys + n, rdkeys, rnchildren * sizeof(*rdkeys));
@@ -332,16 +246,15 @@ static void nilfs_btree_node_move_right(struct nilfs_btree *btree,
 }
 
 /* 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)
+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, btree);
+        dptrs = nilfs_btree_node_dptrs(node, ncmax);
         nchildren = nilfs_btree_node_get_nchildren(node);
         if (index < nchildren) {
                 memmove(dkeys + index + 1, dkeys + index,
@@ -349,16 +262,15 @@ static void nilfs_btree_node_insert(struct nilfs_btree *btree,
                 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);
+        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 *btree,
-                                    struct nilfs_btree_node *node,
-                                    __u64 *keyp, __u64 *ptrp, int index)
+static void nilfs_btree_node_delete(struct nilfs_btree_node *node, int index,
+                                    __u64 *keyp, __u64 *ptrp, int ncmax)
 {
         __u64 key;
         __u64 ptr;
@@ -367,9 +279,9 @@ static void nilfs_btree_node_delete(struct nilfs_btree *btree,
         int nchildren;
 
         dkeys = nilfs_btree_node_dkeys(node);
-        dptrs = nilfs_btree_node_dptrs(node, btree);
-        key = nilfs_bmap_dkey_to_key(dkeys[index]);
-        ptr = nilfs_bmap_dptr_to_ptr(dptrs[index]);
+        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;
@@ -425,40 +337,92 @@ static int nilfs_btree_node_lookup(const struct nilfs_btree_node *node,
         return s == 0;
 }
 
-static inline struct nilfs_btree_node *
-nilfs_btree_get_root(const struct nilfs_btree *btree)
+/**
+ * nilfs_btree_node_broken - verify consistency of btree node
+ * @node: btree node block to be examined
+ * @size: node size (in bytes)
+ * @blocknr: block number
+ *
+ * Return Value: If node is broken, 1 is returned. Otherwise, 0 is returned.
+ */
+static int nilfs_btree_node_broken(const struct nilfs_btree_node *node,
+                                   size_t size, sector_t blocknr)
+{
+        int level, flags, nchildren;
+        int ret = 0;
+
+        level = nilfs_btree_node_get_level(node);
+        flags = nilfs_btree_node_get_flags(node);
+        nchildren = nilfs_btree_node_get_nchildren(node);
+
+        if (unlikely(level < NILFS_BTREE_LEVEL_NODE_MIN ||
+                     level >= NILFS_BTREE_LEVEL_MAX ||
+                     (flags & NILFS_BTREE_NODE_ROOT) ||
+                     nchildren < 0 ||
+                     nchildren > NILFS_BTREE_NODE_NCHILDREN_MAX(size))) {
+                printk(KERN_CRIT "NILFS: bad btree node (blocknr=%llu): "
+                       "level = %d, flags = 0x%x, nchildren = %d\n",
+                       (unsigned long long)blocknr, level, flags, nchildren);
+                ret = 1;
+        }
+        return ret;
+}
+
+int nilfs_btree_broken_node_block(struct buffer_head *bh)
 {
-        return (struct nilfs_btree_node *)btree->bt_bmap.b_u.u_data;
+        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 inline struct nilfs_btree_node *
+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 inline struct nilfs_btree_node *
+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 inline int nilfs_btree_height(const struct nilfs_btree *btree)
+static int nilfs_btree_height(const struct nilfs_bmap *btree)
 {
         return nilfs_btree_node_get_level(nilfs_btree_get_root(btree)) + 1;
 }
 
-static inline struct nilfs_btree_node *
-nilfs_btree_get_node(const struct nilfs_btree *btree,
+static struct nilfs_btree_node *
+nilfs_btree_get_node(const struct nilfs_bmap *btree,
                      const struct nilfs_btree_path *path,
-                     int level)
+                     int level, int *ncmaxp)
 {
-        return (level == nilfs_btree_height(btree) - 1) ?
-                nilfs_btree_get_root(btree) :
-                nilfs_btree_get_nonroot_node(path, level);
+        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 inline int
+static int
 nilfs_btree_bad_node(struct nilfs_btree_node *node, int level)
 {
         if (unlikely(nilfs_btree_node_get_level(node) != level)) {
@@ -470,13 +434,83 @@ nilfs_btree_bad_node(struct nilfs_btree_node *node, int level)
         return 0;
 }
 
-static int nilfs_btree_do_lookup(const struct nilfs_btree *btree,
+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)
+                                 __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, ret;
+        int level, index, found, ncmax, ret;
 
         node = nilfs_btree_get_root(btree);
         level = nilfs_btree_node_get_level(node);
@@ -484,14 +518,27 @@ static int nilfs_btree_do_lookup(const struct nilfs_btree *btree,
                 return -ENOENT;
 
         found = nilfs_btree_node_lookup(node, key, &index);
-        ptr = nilfs_btree_node_get_ptr(btree, node, index);
+        ptr = nilfs_btree_node_get_ptr(node, index,
+                                       NILFS_BTREE_ROOT_NCHILDREN_MAX);
         path[level].bp_bh = NULL;
         path[level].bp_index = index;
 
-        for (level--; level >= minlevel; level--) {
-                ret = nilfs_btree_get_block(btree, ptr, &path[level].bp_bh);
+        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;
@@ -499,9 +546,9 @@ static int nilfs_btree_do_lookup(const struct nilfs_btree *btree,
                         found = nilfs_btree_node_lookup(node, key, &index);
                 else
                         index = 0;
-                if (index < nilfs_btree_node_nchildren_max(node, btree))
-                        ptr = nilfs_btree_node_get_ptr(btree, node, index);
-                else {
+                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;
@@ -517,22 +564,24 @@ static int nilfs_btree_do_lookup(const struct nilfs_btree *btree,
         return 0;
 }
 
-static int nilfs_btree_do_lookup_last(const struct nilfs_btree *btree,
+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, ret;
+        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(btree, node, 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);
 
         for (level--; level > 0; level--) {
                 ret = nilfs_btree_get_block(btree, ptr, &path[level].bp_bh);
@@ -542,7 +591,7 @@ static int nilfs_btree_do_lookup_last(const struct nilfs_btree *btree,
                 if (nilfs_btree_bad_node(node, level))
                         return -EINVAL;
                 index = nilfs_btree_node_get_nchildren(node) - 1;
-                ptr = nilfs_btree_node_get_ptr(btree, node, index);
+                ptr = nilfs_btree_node_get_ptr(node, index, ncmax);
                 path[level].bp_index = index;
         }
 
@@ -554,53 +603,45 @@ static int nilfs_btree_do_lookup_last(const struct nilfs_btree *btree,
         return 0;
 }
 
-static int nilfs_btree_lookup(const struct nilfs_bmap *bmap,
+static int nilfs_btree_lookup(const struct nilfs_bmap *btree,
                               __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();
         if (path == NULL)
                 return -ENOMEM;
-        nilfs_btree_init_path(path);
 
-        ret = nilfs_btree_do_lookup(btree, path, key, &ptr, level);
-
-        if (ptrp != NULL)
-                *ptrp = ptr;
+        ret = nilfs_btree_do_lookup(btree, path, key, ptrp, level, 0);
 
-        nilfs_btree_release_path(path);
         nilfs_btree_free_path(path);
 
         return ret;
 }
 
-static int nilfs_btree_lookup_contig(const struct nilfs_bmap *bmap,
+static int nilfs_btree_lookup_contig(const struct nilfs_bmap *btree,
                                      __u64 key, __u64 *ptrp, unsigned maxblocks)
 {
-        struct nilfs_btree *btree = (struct nilfs_btree *)bmap;
         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;
+        int ret, cnt, index, maxlevel, ncmax;
+        struct nilfs_btree_readahead_info p;
 
         path = nilfs_btree_alloc_path();
         if (path == NULL)
                 return -ENOMEM;
-        nilfs_btree_init_path(path);
-        ret = nilfs_btree_do_lookup(btree, path, key, &ptr, level);
+
+        ret = nilfs_btree_do_lookup(btree, path, key, &ptr, level, 1);
         if (ret < 0)
                 goto out;
 
-        if (NILFS_BMAP_USE_VBN(bmap)) {
-                dat = nilfs_bmap_get_dat(bmap);
+        if (NILFS_BMAP_USE_VBN(btree)) {
+                dat = nilfs_bmap_get_dat(btree);
                 ret = nilfs_dat_translate(dat, ptr, &blocknr);
                 if (ret < 0)
                         goto out;
@@ -611,14 +652,14 @@ static int nilfs_btree_lookup_contig(const struct nilfs_bmap *bmap,
                 goto end;
 
         maxlevel = nilfs_btree_height(btree) - 1;
-        node = nilfs_btree_get_node(btree, path, level);
+        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(btree, node, index);
+                        ptr2 = nilfs_btree_node_get_ptr(node, index, ncmax);
                         if (dat) {
                                 ret = nilfs_dat_translate(dat, ptr2, &blocknr);
                                 if (ret < 0)
@@ -634,20 +675,24 @@ static int nilfs_btree_lookup_contig(const struct nilfs_bmap *bmap,
                         break;
 
                 /* look-up right sibling node */
-                node = nilfs_btree_get_node(btree, path, level + 1);
-                index = path[level + 1].bp_index + 1;
-                if (index >= nilfs_btree_node_get_nchildren(node) ||
-                    nilfs_btree_node_get_key(node, index) != key + cnt)
+                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(btree, node, index);
-                path[level + 1].bp_index = index;
+                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);
+
+                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;
         }
@@ -655,12 +700,11 @@ static int nilfs_btree_lookup_contig(const struct nilfs_bmap *bmap,
         *ptrp = ptr;
         ret = cnt;
  out:
-        nilfs_btree_release_path(path);
         nilfs_btree_free_path(path);
         return ret;
 }
 
-static void nilfs_btree_promote_key(struct nilfs_btree *btree,
+static void nilfs_btree_promote_key(struct nilfs_bmap *btree,
                                     struct nilfs_btree_path *path,
                                     int level, __u64 key)
 {
@@ -682,16 +726,18 @@ static void nilfs_btree_promote_key(struct nilfs_btree *btree,
         }
 }
 
-static void nilfs_btree_do_insert(struct nilfs_btree *btree,
+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);
-                nilfs_btree_node_insert(btree, node, *keyp, *ptrp,
-                                        path[level].bp_index);
+                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))
                         nilfs_btnode_mark_dirty(path[level].bp_bh);
 
@@ -701,22 +747,24 @@ static void nilfs_btree_do_insert(struct nilfs_btree *btree,
                                                                          0));
         } else {
                 node = nilfs_btree_get_root(btree);
-                nilfs_btree_node_insert(btree, node, *keyp, *ptrp,
-                                        path[level].bp_index);
+                nilfs_btree_node_insert(node, path[level].bp_index,
+                                        *keyp, *ptrp,
+                                        NILFS_BTREE_ROOT_NCHILDREN_MAX);
         }
 }
 
-static void nilfs_btree_carry_left(struct nilfs_btree *btree,
+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;
+        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;
@@ -726,7 +774,7 @@ static void nilfs_btree_carry_left(struct nilfs_btree *btree,
                 move = 1;
         }
 
-        nilfs_btree_node_move_left(btree, left, node, n);
+        nilfs_btree_node_move_left(left, node, n, ncblk, ncblk);
 
         if (!buffer_dirty(path[level].bp_bh))
                 nilfs_btnode_mark_dirty(path[level].bp_bh);
@@ -751,17 +799,18 @@ static void nilfs_btree_carry_left(struct nilfs_btree *btree,
         nilfs_btree_do_insert(btree, path, level, keyp, ptrp);
 }
 
-static void nilfs_btree_carry_right(struct nilfs_btree *btree,
+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;
+        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;
@@ -771,7 +820,7 @@ static void nilfs_btree_carry_right(struct nilfs_btree *btree,
                 move = 1;
         }
 
-        nilfs_btree_node_move_right(btree, node, right, n);
+        nilfs_btree_node_move_right(node, right, n, ncblk, ncblk);
 
         if (!buffer_dirty(path[level].bp_bh))
                 nilfs_btnode_mark_dirty(path[level].bp_bh);
@@ -797,18 +846,19 @@ static void nilfs_btree_carry_right(struct nilfs_btree *btree,
         nilfs_btree_do_insert(btree, path, level, keyp, ptrp);
 }
 
-static void nilfs_btree_split(struct nilfs_btree *btree,
+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;
+        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;
@@ -817,7 +867,7 @@ static void nilfs_btree_split(struct nilfs_btree *btree,
                 move = 1;
         }
 
-        nilfs_btree_node_move_right(btree, node, right, n);
+        nilfs_btree_node_move_right(node, right, n, ncblk, ncblk);
 
         if (!buffer_dirty(path[level].bp_bh))
                 nilfs_btnode_mark_dirty(path[level].bp_bh);
@@ -829,8 +879,8 @@ static void nilfs_btree_split(struct nilfs_btree *btree,
 
         if (move) {
                 path[level].bp_index -= nilfs_btree_node_get_nchildren(node);
-                nilfs_btree_node_insert(btree, right, *keyp, *ptrp,
-                                        path[level].bp_index);
+                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;
@@ -851,19 +901,21 @@ static void nilfs_btree_split(struct nilfs_btree *btree,
         path[level + 1].bp_index++;
 }
 
-static void nilfs_btree_grow(struct nilfs_btree *btree,
+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;
+        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(btree, root, child, n);
+        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))
@@ -878,11 +930,11 @@ static void nilfs_btree_grow(struct nilfs_btree *btree,
         *ptrp = path[level].bp_newreq.bpr_ptr;
 }
 
-static __u64 nilfs_btree_find_near(const struct nilfs_btree *btree,
+static __u64 nilfs_btree_find_near(const struct nilfs_bmap *btree,
                                    const struct nilfs_btree_path *path)
 {
         struct nilfs_btree_node *node;
-        int level;
+        int level, ncmax;
 
         if (path == NULL)
                 return NILFS_BMAP_INVALID_PTR;
@@ -890,29 +942,30 @@ static __u64 nilfs_btree_find_near(const struct nilfs_btree *btree,
         /* 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);
+                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);
-                return nilfs_btree_node_get_ptr(btree, node,
-                                                path[level].bp_index);
+                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_btree *btree,
+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->bt_bmap, key);
+        ptr = nilfs_bmap_find_target_seq(btree, key);
         if (ptr != NILFS_BMAP_INVALID_PTR)
                 /* sequential access */
                 return ptr;
@@ -923,17 +976,10 @@ static __u64 nilfs_btree_find_target_v(const struct nilfs_btree *btree,
                         return ptr;
         }
         /* block group */
-        return nilfs_bmap_find_target_in_group(&btree->bt_bmap);
+        return nilfs_bmap_find_target_in_group(btree);
 }
 
-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,
+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)
@@ -941,79 +987,78 @@ static int nilfs_btree_prepare_insert(struct nilfs_btree *btree,
         struct buffer_head *bh;
         struct nilfs_btree_node *node, *parent, *sib;
         __u64 sibptr;
-        int pindex, level, ret;
+        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->bt_bmap)) {
+        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->bt_bmap);
+                dat = nilfs_bmap_get_dat(btree);
         }
 
-        ret = nilfs_bmap_prepare_alloc_ptr(&btree->bt_bmap,
-                                           &path[level].bp_newreq, dat);
+        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) <
-                    nilfs_btree_node_nchildren_max(node, btree)) {
+                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);
+                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(btree, parent,
-                                                          pindex - 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) <
-                            nilfs_btree_node_nchildren_max(sib, btree)) {
+                        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
+                        } else {
                                 brelse(bh);
+                        }
                 }
 
                 /* right sibling */
-                if (pindex <
-                    nilfs_btree_node_get_nchildren(parent) - 1) {
-                        sibptr = nilfs_btree_node_get_ptr(btree, parent,
-                                                          pindex + 1);
+                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) <
-                            nilfs_btree_node_nchildren_max(sib, btree)) {
+                        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
+                        } 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->bt_bmap,
+                ret = nilfs_bmap_prepare_alloc_ptr(btree,
                                                    &path[level].bp_newreq, dat);
                 if (ret < 0)
                         goto err_out_child_node;
@@ -1025,9 +1070,8 @@ static int nilfs_btree_prepare_insert(struct nilfs_btree *btree,
 
                 stats->bs_nblocks++;
 
-                nilfs_btree_node_init(btree,
-                                      (struct nilfs_btree_node *)bh->b_data,
-                                      0, level, 0, NULL, NULL);
+                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;
         }
@@ -1035,7 +1079,7 @@ static int nilfs_btree_prepare_insert(struct nilfs_btree *btree,
         /* root */
         node = nilfs_btree_get_root(btree);
         if (nilfs_btree_node_get_nchildren(node) <
-            nilfs_btree_node_nchildren_max(node, btree)) {
+            NILFS_BTREE_ROOT_NCHILDREN_MAX) {
                 path[level].bp_op = nilfs_btree_do_insert;
                 stats->bs_nblocks++;
                 goto out;
@@ -1043,8 +1087,7 @@ static int nilfs_btree_prepare_insert(struct nilfs_btree *btree,
 
         /* grow */
         path[level].bp_newreq.bpr_ptr = path[level - 1].bp_newreq.bpr_ptr + 1;
-        ret = nilfs_bmap_prepare_alloc_ptr(&btree->bt_bmap,
-                                           &path[level].bp_newreq, dat);
+        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,
@@ -1052,8 +1095,8 @@ static int nilfs_btree_prepare_insert(struct nilfs_btree *btree,
         if (ret < 0)
                 goto err_out_curr_node;
 
-        nilfs_btree_node_init(btree, (struct nilfs_btree_node *)bh->b_data,
-                              0, level, 0, NULL, NULL);
+        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;
 
@@ -1070,25 +1113,22 @@ static int nilfs_btree_prepare_insert(struct nilfs_btree *btree,
 
         /* error */
  err_out_curr_node:
-        nilfs_bmap_abort_alloc_ptr(&btree->bt_bmap, &path[level].bp_newreq,
-                                   dat);
+        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->bt_bmap,
-                                           &path[level].bp_newreq, dat);
+                nilfs_bmap_abort_alloc_ptr(btree, &path[level].bp_newreq, dat);
 
         }
 
-        nilfs_bmap_abort_alloc_ptr(&btree->bt_bmap, &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_btree *btree,
+static void nilfs_btree_commit_insert(struct nilfs_bmap *btree,
                                       struct nilfs_btree_path *path,
                                       int maxlevel, __u64 key, __u64 ptr)
 {
@@ -1097,36 +1137,33 @@ static void nilfs_btree_commit_insert(struct nilfs_btree *btree,
 
         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->bt_bmap)) {
-                nilfs_btree_set_target_v(btree, key, ptr);
-                dat = nilfs_bmap_get_dat(&btree->bt_bmap);
+        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->bt_bmap,
+                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->bt_bmap))
-                nilfs_bmap_set_dirty(&btree->bt_bmap);
+        if (!nilfs_bmap_dirty(btree))
+                nilfs_bmap_set_dirty(btree);
 }
 
-static int nilfs_btree_insert(struct nilfs_bmap *bmap, __u64 key, __u64 ptr)
+static int nilfs_btree_insert(struct nilfs_bmap *btree, __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();
         if (path == NULL)
                 return -ENOMEM;
-        nilfs_btree_init_path(path);
 
         ret = nilfs_btree_do_lookup(btree, path, key, NULL,
-                                    NILFS_BTREE_LEVEL_NODE_MIN);
+                                    NILFS_BTREE_LEVEL_NODE_MIN, 0);
         if (ret != -ENOENT) {
                 if (ret == 0)
                         ret = -EEXIST;
@@ -1137,24 +1174,25 @@ static int nilfs_btree_insert(struct nilfs_bmap *bmap, __u64 key, __u64 ptr)
         if (ret < 0)
                 goto out;
         nilfs_btree_commit_insert(btree, path, level, key, ptr);
-        nilfs_bmap_add_blocks(bmap, stats.bs_nblocks);
+        nilfs_bmap_add_blocks(btree, stats.bs_nblocks);
 
  out:
-        nilfs_btree_release_path(path);
         nilfs_btree_free_path(path);
         return ret;
 }
 
-static void nilfs_btree_do_delete(struct nilfs_btree *btree,
+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);
-                nilfs_btree_node_delete(btree, node, keyp, ptrp,
-                                        path[level].bp_index);
+                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))
                         nilfs_btnode_mark_dirty(path[level].bp_bh);
                 if (path[level].bp_index == 0)
@@ -1162,17 +1200,18 @@ static void nilfs_btree_do_delete(struct nilfs_btree *btree,
                                 nilfs_btree_node_get_key(node, 0));
         } else {
                 node = nilfs_btree_get_root(btree);
-                nilfs_btree_node_delete(btree, node, keyp, ptrp,
-                                        path[level].bp_index);
+                nilfs_btree_node_delete(node, path[level].bp_index,
+                                        keyp, ptrp,
+                                        NILFS_BTREE_ROOT_NCHILDREN_MAX);
         }
 }
 
-static void nilfs_btree_borrow_left(struct nilfs_btree *btree,
+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;
+        int nchildren, lnchildren, n, ncblk;
 
         nilfs_btree_do_delete(btree, path, level, keyp, ptrp);
 
@@ -1180,10 +1219,11 @@ static void nilfs_btree_borrow_left(struct nilfs_btree *btree,
         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(btree, left, node, n);
+        nilfs_btree_node_move_right(left, node, n, ncblk, ncblk);
 
         if (!buffer_dirty(path[level].bp_bh))
                 nilfs_btnode_mark_dirty(path[level].bp_bh);
@@ -1198,12 +1238,12 @@ static void nilfs_btree_borrow_left(struct nilfs_btree *btree,
         path[level].bp_index += n;
 }
 
-static void nilfs_btree_borrow_right(struct nilfs_btree *btree,
+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;
+        int nchildren, rnchildren, n, ncblk;
 
         nilfs_btree_do_delete(btree, path, level, keyp, ptrp);
 
@@ -1211,10 +1251,11 @@ static void nilfs_btree_borrow_right(struct nilfs_btree *btree,
         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(btree, node, right, n);
+        nilfs_btree_node_move_left(node, right, n, ncblk, ncblk);
 
         if (!buffer_dirty(path[level].bp_bh))
                 nilfs_btnode_mark_dirty(path[level].bp_bh);
@@ -1230,21 +1271,22 @@ static void nilfs_btree_borrow_right(struct nilfs_btree *btree,
         path[level].bp_sib_bh = NULL;
 }
 
-static void nilfs_btree_concat_left(struct nilfs_btree *btree,
+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;
+        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(btree, left, node, n);
+        nilfs_btree_node_move_left(left, node, n, ncblk, ncblk);
 
         if (!buffer_dirty(path[level].bp_sib_bh))
                 nilfs_btnode_mark_dirty(path[level].bp_sib_bh);
@@ -1255,21 +1297,22 @@ static void nilfs_btree_concat_left(struct nilfs_btree *btree,
         path[level].bp_index += nilfs_btree_node_get_nchildren(left);
 }
 
-static void nilfs_btree_concat_right(struct nilfs_btree *btree,
+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;
+        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(btree, node, right, n);
+        nilfs_btree_node_move_left(node, right, n, ncblk, ncblk);
 
         if (!buffer_dirty(path[level].bp_bh))
                 nilfs_btnode_mark_dirty(path[level].bp_bh);
@@ -1279,29 +1322,32 @@ static void nilfs_btree_concat_right(struct nilfs_btree *btree,
         path[level + 1].bp_index++;
 }
 
-static void nilfs_btree_shrink(struct nilfs_btree *btree,
+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;
+        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(btree, root, NULL, NULL, 0);
+        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(btree, root, child, n);
+        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 int nilfs_btree_prepare_delete(struct nilfs_btree *btree,
+static int nilfs_btree_prepare_delete(struct nilfs_bmap *btree,
                                       struct nilfs_btree_path *path,
                                       int *levelp,
                                       struct nilfs_bmap_stats *stats,
@@ -1310,42 +1356,43 @@ static int nilfs_btree_prepare_delete(struct nilfs_btree *btree,
         struct buffer_head *bh;
         struct nilfs_btree_node *node, *parent, *sib;
         __u64 sibptr;
-        int pindex, level, ret;
+        int pindex, 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;
              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(btree, node,
-                                                 path[level].bp_index);
-                ret = nilfs_bmap_prepare_end_ptr(&btree->bt_bmap,
+                        nilfs_btree_node_get_ptr(node, path[level].bp_index,
+                                                 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) >
-                    nilfs_btree_node_nchildren_min(node, btree)) {
+                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);
+                parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
                 pindex = path[level + 1].bp_index;
 
                 if (pindex > 0) {
                         /* left sibling */
-                        sibptr = nilfs_btree_node_get_ptr(btree, parent,
-                                                          pindex - 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_curr_node;
                         sib = (struct nilfs_btree_node *)bh->b_data;
-                        if (nilfs_btree_node_get_nchildren(sib) >
-                            nilfs_btree_node_nchildren_min(sib, btree)) {
+                        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++;
@@ -1359,14 +1406,13 @@ static int nilfs_btree_prepare_delete(struct nilfs_btree *btree,
                 } else if (pindex <
                            nilfs_btree_node_get_nchildren(parent) - 1) {
                         /* right sibling */
-                        sibptr = nilfs_btree_node_get_ptr(btree, parent,
-                                                          pindex + 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_curr_node;
                         sib = (struct nilfs_btree_node *)bh->b_data;
-                        if (nilfs_btree_node_get_nchildren(sib) >
-                            nilfs_btree_node_nchildren_min(sib, btree)) {
+                        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++;
@@ -1397,10 +1443,10 @@ static int nilfs_btree_prepare_delete(struct nilfs_btree *btree,
 
         node = nilfs_btree_get_root(btree);
         path[level].bp_oldreq.bpr_ptr =
-                nilfs_btree_node_get_ptr(btree, node, path[level].bp_index);
+                nilfs_btree_node_get_ptr(node, path[level].bp_index,
+                                         NILFS_BTREE_ROOT_NCHILDREN_MAX);
 
-        ret = nilfs_bmap_prepare_end_ptr(&btree->bt_bmap,
-                                         &path[level].bp_oldreq, dat);
+        ret = nilfs_bmap_prepare_end_ptr(btree, &path[level].bp_oldreq, dat);
         if (ret < 0)
                 goto err_out_child_node;
 
@@ -1415,99 +1461,87 @@ static int nilfs_btree_prepare_delete(struct nilfs_btree *btree,
 
         /* error */
  err_out_curr_node:
-        nilfs_bmap_abort_end_ptr(&btree->bt_bmap, &path[level].bp_oldreq, dat);
+        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->bt_bmap,
-                                         &path[level].bp_oldreq, dat);
+                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_btree *btree,
+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->bt_bmap,
-                                          &path[level].bp_oldreq, dat);
+                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->bt_bmap))
-                nilfs_bmap_set_dirty(&btree->bt_bmap);
+        if (!nilfs_bmap_dirty(btree))
+                nilfs_bmap_set_dirty(btree);
 }
 
-static int nilfs_btree_delete(struct nilfs_bmap *bmap, __u64 key)
+static int nilfs_btree_delete(struct nilfs_bmap *btree, __u64 key)
 
 {
-        struct nilfs_btree *btree;
         struct nilfs_btree_path *path;
         struct nilfs_bmap_stats stats;
         struct inode *dat;
         int level, ret;
 
-        btree = (struct nilfs_btree *)bmap;
         path = nilfs_btree_alloc_path();
         if (path == NULL)
                 return -ENOMEM;
-        nilfs_btree_init_path(path);
+
         ret = nilfs_btree_do_lookup(btree, path, key, NULL,
-                                    NILFS_BTREE_LEVEL_NODE_MIN);
+                                    NILFS_BTREE_LEVEL_NODE_MIN, 0);
         if (ret < 0)
                 goto out;
 
 
-        dat = NILFS_BMAP_USE_VBN(&btree->bt_bmap) ?
-                nilfs_bmap_get_dat(&btree->bt_bmap) : NULL;
+        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_bmap_sub_blocks(bmap, stats.bs_nblocks);
+        nilfs_bmap_sub_blocks(btree, stats.bs_nblocks);
 
 out:
-        nilfs_btree_release_path(path);
         nilfs_btree_free_path(path);
         return ret;
 }
 
-static int nilfs_btree_last_key(const struct nilfs_bmap *bmap, __u64 *keyp)
+static int nilfs_btree_last_key(const struct nilfs_bmap *btree, __u64 *keyp)
 {
-        struct nilfs_btree *btree;
         struct nilfs_btree_path *path;
         int ret;
 
-        btree = (struct nilfs_btree *)bmap;
         path = nilfs_btree_alloc_path();
         if (path == NULL)
                 return -ENOMEM;
-        nilfs_btree_init_path(path);
 
         ret = nilfs_btree_do_lookup_last(btree, path, keyp, NULL);
 
-        nilfs_btree_release_path(path);
         nilfs_btree_free_path(path);
 
         return ret;
 }
 
-static int nilfs_btree_check_delete(struct nilfs_bmap *bmap, __u64 key)
+static int nilfs_btree_check_delete(struct nilfs_bmap *btree, __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:
@@ -1518,7 +1552,8 @@ static int nilfs_btree_check_delete(struct nilfs_bmap *bmap, __u64 key)
                 nchildren = nilfs_btree_node_get_nchildren(root);
                 if (nchildren > 1)
                         return 0;
-                ptr = nilfs_btree_node_get_ptr(btree, root, 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;
@@ -1538,32 +1573,33 @@ static int nilfs_btree_check_delete(struct nilfs_bmap *bmap, __u64 key)
         return (maxkey == key) && (nextmaxkey < NILFS_BMAP_LARGE_LOW);
 }
 
-static int nilfs_btree_gather_data(struct nilfs_bmap *bmap,
+static int nilfs_btree_gather_data(struct nilfs_bmap *btree,
                                    __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;
+        int nchildren, ncmax, i, ret;
 
-        btree = (struct nilfs_btree *)bmap;
         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(btree, root, 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;
@@ -1574,10 +1610,10 @@ static int nilfs_btree_gather_data(struct nilfs_bmap *bmap,
         if (nchildren < nitems)
                 nitems = nchildren;
         dkeys = nilfs_btree_node_dkeys(node);
-        dptrs = nilfs_btree_node_dptrs(node, btree);
+        dptrs = nilfs_btree_node_dptrs(node, ncmax);
         for (i = 0; i < nitems; i++) {
-                keys[i] = nilfs_bmap_dkey_to_key(dkeys[i]);
-                ptrs[i] = nilfs_bmap_dptr_to_ptr(dptrs[i]);
+                keys[i] = le64_to_cpu(dkeys[i]);
+                ptrs[i] = le64_to_cpu(dptrs[i]);
         }
 
         if (bh != NULL)
@@ -1587,14 +1623,13 @@ static int nilfs_btree_gather_data(struct nilfs_bmap *bmap,
 }
 
 static int
-nilfs_btree_prepare_convert_and_insert(struct nilfs_bmap *bmap, __u64 key,
+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 nilfs_btree *btree = (struct nilfs_btree *)bmap;
         struct inode *dat = NULL;
         int ret;
 
@@ -1602,12 +1637,12 @@ nilfs_btree_prepare_convert_and_insert(struct nilfs_bmap *bmap, __u64 key,
 
         /* for data */
         /* cannot find near ptr */
-        if (NILFS_BMAP_USE_VBN(bmap)) {
+        if (NILFS_BMAP_USE_VBN(btree)) {
                 dreq->bpr_ptr = nilfs_btree_find_target_v(btree, NULL, key);
-                dat = nilfs_bmap_get_dat(bmap);
+                dat = nilfs_bmap_get_dat(btree);
         }
 
-        ret = nilfs_bmap_prepare_alloc_ptr(bmap, dreq, dat);
+        ret = nilfs_bmap_prepare_alloc_ptr(btree, dreq, dat);
         if (ret < 0)
                 return ret;
 
@@ -1615,7 +1650,7 @@ nilfs_btree_prepare_convert_and_insert(struct nilfs_bmap *bmap, __u64 key,
         stats->bs_nblocks++;
         if (nreq != NULL) {
                 nreq->bpr_ptr = dreq->bpr_ptr + 1;
-                ret = nilfs_bmap_prepare_alloc_ptr(bmap, nreq, dat);
+                ret = nilfs_bmap_prepare_alloc_ptr(btree, nreq, dat);
                 if (ret < 0)
                         goto err_out_dreq;
 
@@ -1632,16 +1667,16 @@ nilfs_btree_prepare_convert_and_insert(struct nilfs_bmap *bmap, __u64 key,
 
         /* error */
  err_out_nreq:
-        nilfs_bmap_abort_alloc_ptr(bmap, nreq, dat);
+        nilfs_bmap_abort_alloc_ptr(btree, nreq, dat);
  err_out_dreq:
-        nilfs_bmap_abort_alloc_ptr(bmap, dreq, dat);
+        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 *bmap,
+nilfs_btree_commit_convert_and_insert(struct nilfs_bmap *btree,
                                       __u64 key, __u64 ptr,
                                       const __u64 *keys, const __u64 *ptrs,
                                       int n,
@@ -1649,57 +1684,59 @@ nilfs_btree_commit_convert_and_insert(struct nilfs_bmap *bmap,
                                       union nilfs_bmap_ptr_req *nreq,
                                       struct buffer_head *bh)
 {
-        struct nilfs_btree *btree = (struct nilfs_btree *)bmap;
         struct nilfs_btree_node *node;
         struct inode *dat;
         __u64 tmpptr;
+        int ncblk;
 
         /* free resources */
-        if (bmap->b_ops->bop_clear != NULL)
-                bmap->b_ops->bop_clear(bmap);
+        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(bmap) ? nilfs_bmap_get_dat(bmap) : NULL;
-        nilfs_btree_init(bmap);
+        dat = NILFS_BMAP_USE_VBN(btree) ? nilfs_bmap_get_dat(btree) : NULL;
+        nilfs_btree_init(btree);
         if (nreq != NULL) {
-                nilfs_bmap_commit_alloc_ptr(bmap, dreq, dat);
-                nilfs_bmap_commit_alloc_ptr(bmap, nreq, dat);
+                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;
-                nilfs_btree_node_init(btree, node, 0, 1, n, keys, ptrs);
-                nilfs_btree_node_insert(btree, node,
-                                        key, dreq->bpr_ptr, n);
+                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))
                         nilfs_btnode_mark_dirty(bh);
-                if (!nilfs_bmap_dirty(bmap))
-                        nilfs_bmap_set_dirty(bmap);
+                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(btree, node, NILFS_BTREE_NODE_ROOT,
-                                      2, 1, &keys[0], &tmpptr);
+                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(bmap, dreq, dat);
+                nilfs_bmap_commit_alloc_ptr(btree, dreq, dat);
 
                 /* 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);
+                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(bmap))
-                nilfs_btree_set_target_v(btree, key, dreq->bpr_ptr);
+        if (NILFS_BMAP_USE_VBN(btree))
+                nilfs_bmap_set_target_v(btree, key, dreq->bpr_ptr);
 }
 
 /**
@@ -1711,7 +1748,7 @@ nilfs_btree_commit_convert_and_insert(struct nilfs_bmap *bmap,
  * @ptrs:
  * @n:
  */
-int nilfs_btree_convert_and_insert(struct nilfs_bmap *bmap,
+int nilfs_btree_convert_and_insert(struct nilfs_bmap *btree,
                                    __u64 key, __u64 ptr,
                                    const __u64 *keys, const __u64 *ptrs, int n)
 {
@@ -1724,7 +1761,7 @@ int nilfs_btree_convert_and_insert(struct nilfs_bmap *bmap,
                 di = &dreq;
                 ni = NULL;
         } else if ((n + 1) <= NILFS_BTREE_NODE_NCHILDREN_MAX(
-                           1 << bmap->b_inode->i_blkbits)) {
+                           1 << btree->b_inode->i_blkbits)) {
                 di = &dreq;
                 ni = &nreq;
         } else {
@@ -1733,17 +1770,17 @@ int nilfs_btree_convert_and_insert(struct nilfs_bmap *bmap,
                 BUG();
         }
 
-        ret = nilfs_btree_prepare_convert_and_insert(bmap, key, di, ni, &bh,
+        ret = nilfs_btree_prepare_convert_and_insert(btree, key, di, ni, &bh,
                                                      &stats);
         if (ret < 0)
                 return ret;
-        nilfs_btree_commit_convert_and_insert(bmap, key, ptr, keys, ptrs, n,
+        nilfs_btree_commit_convert_and_insert(btree, key, ptr, keys, ptrs, n,
                                               di, ni, bh);
-        nilfs_bmap_add_blocks(bmap, stats.bs_nblocks);
+        nilfs_bmap_add_blocks(btree, stats.bs_nblocks);
         return 0;
 }
 
-static int nilfs_btree_propagate_p(struct nilfs_btree *btree,
+static int nilfs_btree_propagate_p(struct nilfs_bmap *btree,
                                    struct nilfs_btree_path *path,
                                    int level,
                                    struct buffer_head *bh)
@@ -1755,17 +1792,17 @@ static int nilfs_btree_propagate_p(struct nilfs_btree *btree,
         return 0;
 }
 
-static int nilfs_btree_prepare_update_v(struct nilfs_btree *btree,
+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 ret;
+        int ncmax, ret;
 
-        parent = nilfs_btree_get_node(btree, path, level + 1);
+        parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
         path[level].bp_oldreq.bpr_ptr =
-                nilfs_btree_node_get_ptr(btree, parent,
-                                         path[level + 1].bp_index);
+                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);
@@ -1777,7 +1814,7 @@ static int nilfs_btree_prepare_update_v(struct nilfs_btree *btree,
                 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,
+                        &NILFS_BMAP_I(btree)->i_btnode_cache,
                         &path[level].bp_ctxt);
                 if (ret < 0) {
                         nilfs_dat_abort_update(dat,
@@ -1790,30 +1827,31 @@ static int nilfs_btree_prepare_update_v(struct nilfs_btree *btree,
         return 0;
 }
 
-static void nilfs_btree_commit_update_v(struct nilfs_btree *btree,
+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->bt_bmap.b_ptr_type == NILFS_BMAP_PTR_VS);
+                                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->bt_bmap)->i_btnode_cache,
+                        &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);
-        nilfs_btree_node_set_ptr(btree, parent, path[level + 1].bp_index,
-                                 path[level].bp_newreq.bpr_ptr);
+        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_btree *btree,
+static void nilfs_btree_abort_update_v(struct nilfs_bmap *btree,
                                        struct nilfs_btree_path *path,
                                        int level, struct inode *dat)
 {
@@ -1821,11 +1859,11 @@ static void nilfs_btree_abort_update_v(struct nilfs_btree *btree,
                                &path[level].bp_newreq.bpr_req);
         if (buffer_nilfs_node(path[level].bp_bh))
                 nilfs_btnode_abort_change_key(
-                        &NILFS_BMAP_I(&btree->bt_bmap)->i_btnode_cache,
+                        &NILFS_BMAP_I(btree)->i_btnode_cache,
                         &path[level].bp_ctxt);
 }
 
-static int nilfs_btree_prepare_propagate_v(struct nilfs_btree *btree,
+static int nilfs_btree_prepare_propagate_v(struct nilfs_bmap *btree,
                                            struct nilfs_btree_path *path,
                                            int minlevel, int *maxlevelp,
                                            struct inode *dat)
@@ -1860,7 +1898,7 @@ static int nilfs_btree_prepare_propagate_v(struct nilfs_btree *btree,
         return ret;
 }
 
-static void nilfs_btree_commit_propagate_v(struct nilfs_btree *btree,
+static void nilfs_btree_commit_propagate_v(struct nilfs_bmap *btree,
                                            struct nilfs_btree_path *path,
                                            int minlevel, int maxlevel,
                                            struct buffer_head *bh,
@@ -1875,14 +1913,15 @@ static void nilfs_btree_commit_propagate_v(struct nilfs_btree *btree,
                 nilfs_btree_commit_update_v(btree, path, level, dat);
 }
 
-static int nilfs_btree_propagate_v(struct nilfs_btree *btree,
+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->bt_bmap);
+        struct inode *dat = nilfs_bmap_get_dat(btree);
         __u64 ptr;
+        int ncmax;
 
         get_bh(bh);
         path[level].bp_bh = bh;
@@ -1892,9 +1931,10 @@ static int nilfs_btree_propagate_v(struct nilfs_btree *btree,
                 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);
+                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;
@@ -1908,10 +1948,9 @@ static int nilfs_btree_propagate_v(struct nilfs_btree *btree,
         return ret;
 }
 
-static int nilfs_btree_propagate(const struct nilfs_bmap *bmap,
+static int nilfs_btree_propagate(struct nilfs_bmap *btree,
                                  struct buffer_head *bh)
 {
-        struct nilfs_btree *btree;
         struct nilfs_btree_path *path;
         struct nilfs_btree_node *node;
         __u64 key;
@@ -1919,22 +1958,20 @@ static int nilfs_btree_propagate(const struct nilfs_bmap *bmap,
 
         WARN_ON(!buffer_dirty(bh));
 
-        btree = (struct nilfs_btree *)bmap;
         path = nilfs_btree_alloc_path();
         if (path == NULL)
                 return -ENOMEM;
-        nilfs_btree_init_path(path);
 
         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(bmap, bh);
+                key = nilfs_bmap_data_get_key(btree, bh);
                 level = NILFS_BTREE_LEVEL_DATA;
         }
 
-        ret = nilfs_btree_do_lookup(btree, path, key, NULL, level + 1);
+        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",
@@ -1942,24 +1979,23 @@ static int nilfs_btree_propagate(const struct nilfs_bmap *bmap,
                 goto out;
         }
 
-        ret = NILFS_BMAP_USE_VBN(bmap) ?
+        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_release_path(path);
         nilfs_btree_free_path(path);
 
         return ret;
 }
 
-static int nilfs_btree_propagate_gc(const struct nilfs_bmap *bmap,
+static int nilfs_btree_propagate_gc(struct nilfs_bmap *btree,
                                     struct buffer_head *bh)
 {
-        return nilfs_dat_mark_dirty(nilfs_bmap_get_dat(bmap), bh->b_blocknr);
+        return nilfs_dat_mark_dirty(nilfs_bmap_get_dat(btree), bh->b_blocknr);
 }
 
-static void nilfs_btree_add_dirty_buffer(struct nilfs_btree *btree,
+static void nilfs_btree_add_dirty_buffer(struct nilfs_bmap *btree,
                                          struct list_head *lists,
                                          struct buffer_head *bh)
 {
@@ -1973,6 +2009,18 @@ static void nilfs_btree_add_dirty_buffer(struct nilfs_btree *btree,
         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;
@@ -1983,11 +2031,10 @@ static void nilfs_btree_add_dirty_buffer(struct nilfs_btree *btree,
         list_add_tail(&bh->b_assoc_buffers, head);
 }
 
-static void nilfs_btree_lookup_dirty_buffers(struct nilfs_bmap *bmap,
+static void nilfs_btree_lookup_dirty_buffers(struct nilfs_bmap *btree,
                                              struct list_head *listp)
 {
-        struct nilfs_btree *btree = (struct nilfs_btree *)bmap;
-        struct address_space *btcache = &NILFS_BMAP_I(bmap)->i_btnode_cache;
+        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;
@@ -2021,7 +2068,7 @@ static void nilfs_btree_lookup_dirty_buffers(struct nilfs_bmap *bmap,
                 list_splice_tail(&lists[level], listp);
 }
 
-static int nilfs_btree_assign_p(struct nilfs_btree *btree,
+static int nilfs_btree_assign_p(struct nilfs_bmap *btree,
                                 struct nilfs_btree_path *path,
                                 int level,
                                 struct buffer_head **bh,
@@ -2031,38 +2078,38 @@ static int nilfs_btree_assign_p(struct nilfs_btree *btree,
         struct nilfs_btree_node *parent;
         __u64 key;
         __u64 ptr;
-        int ret;
+        int ncmax, ret;
 
-        parent = nilfs_btree_get_node(btree, path, level + 1);
-        ptr = nilfs_btree_node_get_ptr(btree, parent,
-                                       path[level + 1].bp_index);
+        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->bt_bmap)->i_btnode_cache,
+                        &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->bt_bmap)->i_btnode_cache,
+                        &NILFS_BMAP_I(btree)->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);
+        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 = nilfs_bmap_key_to_dkey(key);
+        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_btree *btree,
+static int nilfs_btree_assign_v(struct nilfs_bmap *btree,
                                 struct nilfs_btree_path *path,
                                 int level,
                                 struct buffer_head **bh,
@@ -2070,15 +2117,15 @@ static int nilfs_btree_assign_v(struct nilfs_btree *btree,
                                 union nilfs_binfo *binfo)
 {
         struct nilfs_btree_node *parent;
-        struct inode *dat = nilfs_bmap_get_dat(&btree->bt_bmap);
+        struct inode *dat = nilfs_bmap_get_dat(btree);
         __u64 key;
         __u64 ptr;
         union nilfs_bmap_ptr_req req;
-        int ret;
+        int ncmax, ret;
 
-        parent = nilfs_btree_get_node(btree, path, level + 1);
-        ptr = nilfs_btree_node_get_ptr(btree, parent,
-                                       path[level + 1].bp_index);
+        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)
@@ -2087,56 +2134,52 @@ static int nilfs_btree_assign_v(struct nilfs_btree *btree,
 
         key = nilfs_btree_node_get_key(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);
+        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 *bmap,
+static int nilfs_btree_assign(struct nilfs_bmap *btree,
                               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();
         if (path == NULL)
                 return -ENOMEM;
-        nilfs_btree_init_path(path);
 
         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(bmap, *bh);
+                key = nilfs_bmap_data_get_key(btree, *bh);
                 level = NILFS_BTREE_LEVEL_DATA;
         }
 
-        ret = nilfs_btree_do_lookup(btree, path, key, NULL, level + 1);
+        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(bmap) ?
+        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_release_path(path);
         nilfs_btree_free_path(path);
 
         return ret;
 }
 
-static int nilfs_btree_assign_gc(struct nilfs_bmap *bmap,
+static int nilfs_btree_assign_gc(struct nilfs_bmap *btree,
                                  struct buffer_head **bh,
                                  sector_t blocknr,
                                  union nilfs_binfo *binfo)
@@ -2145,7 +2188,7 @@ static int nilfs_btree_assign_gc(struct nilfs_bmap *bmap,
         __u64 key;
         int ret;
 
-        ret = nilfs_dat_move(nilfs_bmap_get_dat(bmap), (*bh)->b_blocknr,
+        ret = nilfs_dat_move(nilfs_bmap_get_dat(btree), (*bh)->b_blocknr,
                              blocknr);
         if (ret < 0)
                 return ret;
@@ -2154,30 +2197,27 @@ static int nilfs_btree_assign_gc(struct nilfs_bmap *bmap,
                 node = (struct nilfs_btree_node *)(*bh)->b_data;
                 key = nilfs_btree_node_get_key(node, 0);
         } else
-                key = nilfs_bmap_data_get_key(bmap, *bh);
+                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 = nilfs_bmap_key_to_dkey(key);
+        binfo->bi_v.bi_blkoff = cpu_to_le64(key);
 
         return 0;
 }
 
-static int nilfs_btree_mark(struct nilfs_bmap *bmap, __u64 key, int level)
+static int nilfs_btree_mark(struct nilfs_bmap *btree, __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();
         if (path == NULL)
                 return -ENOMEM;
-        nilfs_btree_init_path(path);
 
-        ret = nilfs_btree_do_lookup(btree, path, key, &ptr, level + 1);
+        ret = nilfs_btree_do_lookup(btree, path, key, &ptr, level + 1, 0);
         if (ret < 0) {
                 WARN_ON(ret == -ENOENT);
                 goto out;
@@ -2191,11 +2231,10 @@ static int nilfs_btree_mark(struct nilfs_bmap *bmap, __u64 key, int level)
         if (!buffer_dirty(bh))
                 nilfs_btnode_mark_dirty(bh);
         brelse(bh);
-        if (!nilfs_bmap_dirty(&btree->bt_bmap))
-                nilfs_bmap_set_dirty(&btree->bt_bmap);
+        if (!nilfs_bmap_dirty(btree))
+                nilfs_bmap_set_dirty(btree);
 
  out:
-        nilfs_btree_release_path(path);
         nilfs_btree_free_path(path);
         return ret;
 }
@@ -2243,10 +2282,14 @@ static const struct nilfs_bmap_operations nilfs_btree_ops_gc = {
 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));
 }