/*
  * B-tree node operations
  */
-static int nilfs_btree_get_block(const struct nilfs_btree *btree, __u64 ptr,
+static int nilfs_btree_get_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;
        int err;
 
        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);
        node->bn_nchildren = cpu_to_le16(nchildren);
 }
 
-static inline int nilfs_btree_node_size(const struct nilfs_btree *btree)
+static inline int nilfs_btree_node_size(const struct nilfs_bmap *btree)
 {
-       return 1 << btree->bt_bmap.b_inode->i_blkbits;
+       return 1 << btree->b_inode->i_blkbits;
 }
 
 static inline int
 nilfs_btree_node_nchildren_min(const struct nilfs_btree_node *node,
-                              const struct nilfs_btree *btree)
+                              const struct nilfs_bmap *btree)
 {
        return nilfs_btree_node_root(node) ?
                NILFS_BTREE_ROOT_NCHILDREN_MIN :
 
 static inline int
 nilfs_btree_node_nchildren_max(const struct nilfs_btree_node *node,
-                              const struct nilfs_btree *btree)
+                              const struct nilfs_bmap *btree)
 {
        return nilfs_btree_node_root(node) ?
                NILFS_BTREE_ROOT_NCHILDREN_MAX :
 
 static inline __le64 *
 nilfs_btree_node_dptrs(const struct nilfs_btree_node *node,
-                      const struct nilfs_btree *btree)
+                      const struct nilfs_bmap *btree)
 {
        return (__le64 *)(nilfs_btree_node_dkeys(node) +
                          nilfs_btree_node_nchildren_max(node, btree));
 }
 
 static inline __u64
-nilfs_btree_node_get_ptr(const struct nilfs_btree *btree,
+nilfs_btree_node_get_ptr(const struct nilfs_bmap *btree,
                         const struct nilfs_btree_node *node, int index)
 {
        return le64_to_cpu(*(nilfs_btree_node_dptrs(node, btree) + index));
 }
 
 static inline void
-nilfs_btree_node_set_ptr(struct nilfs_btree *btree,
+nilfs_btree_node_set_ptr(struct nilfs_bmap *btree,
                         struct nilfs_btree_node *node, int index, __u64 ptr)
 {
        *(nilfs_btree_node_dptrs(node, btree) + index) = cpu_to_le64(ptr);
 }
 
-static void nilfs_btree_node_init(struct nilfs_btree *btree,
+static void nilfs_btree_node_init(struct nilfs_bmap *btree,
                                  struct nilfs_btree_node *node,
                                  int flags, int level, int nchildren,
                                  const __u64 *keys, const __u64 *ptrs)
 }
 
 /* Assume the buffer heads corresponding to left and right are locked. */
-static void nilfs_btree_node_move_left(struct nilfs_btree *btree,
+static void nilfs_btree_node_move_left(struct nilfs_bmap *btree,
                                       struct nilfs_btree_node *left,
                                       struct nilfs_btree_node *right,
                                       int n)
 }
 
 /* Assume that the buffer heads corresponding to left and right are locked. */
-static void nilfs_btree_node_move_right(struct nilfs_btree *btree,
+static void nilfs_btree_node_move_right(struct nilfs_bmap *btree,
                                        struct nilfs_btree_node *left,
                                        struct nilfs_btree_node *right,
                                        int n)
 }
 
 /* Assume that the buffer head corresponding to node is locked. */
-static void nilfs_btree_node_insert(struct nilfs_btree *btree,
+static void nilfs_btree_node_insert(struct nilfs_bmap *btree,
                                    struct nilfs_btree_node *node,
                                    __u64 key, __u64 ptr, int index)
 {
 }
 
 /* Assume that the buffer head corresponding to node is locked. */
-static void nilfs_btree_node_delete(struct nilfs_btree *btree,
+static void nilfs_btree_node_delete(struct nilfs_bmap *btree,
                                    struct nilfs_btree_node *node,
                                    __u64 *keyp, __u64 *ptrp, int index)
 {
 }
 
 static inline struct nilfs_btree_node *
-nilfs_btree_get_root(const struct nilfs_btree *btree)
+nilfs_btree_get_root(const struct nilfs_bmap *btree)
 {
-       return (struct nilfs_btree_node *)btree->bt_bmap.b_u.u_data;
+       return (struct nilfs_btree_node *)btree->b_u.u_data;
 }
 
 static inline struct nilfs_btree_node *
        return (struct nilfs_btree_node *)path[level].bp_sib_bh->b_data;
 }
 
-static inline int nilfs_btree_height(const struct nilfs_btree *btree)
+static inline 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,
+nilfs_btree_get_node(const struct nilfs_bmap *btree,
                     const struct nilfs_btree_path *path,
                     int level)
 {
        return 0;
 }
 
-static int nilfs_btree_do_lookup(const struct nilfs_btree *btree,
+static int nilfs_btree_do_lookup(const struct nilfs_bmap *btree,
                                 struct nilfs_btree_path *path,
                                 __u64 key, __u64 *ptrp, int minlevel)
 {
        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)
 {
        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;
        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;
        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;
        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)
 {
        }
 }
 
-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)
 {
        }
 }
 
-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)
 {
        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)
 {
        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)
 {
        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)
 {
        *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;
        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;
                        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,
+static void nilfs_btree_set_target_v(struct nilfs_bmap *btree, __u64 key,
                                     __u64 ptr)
 {
-       btree->bt_bmap.b_last_allocated_key = key;
-       btree->bt_bmap.b_last_allocated_ptr = ptr;
+       btree->b_last_allocated_key = key;
+       btree->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)
        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;
 
                /* 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;
 
        /* 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,
 
        /* 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)
 {
 
        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)) {
+       if (NILFS_BMAP_USE_VBN(btree)) {
                nilfs_btree_set_target_v(btree, key, ptr);
-               dat = nilfs_bmap_get_dat(&btree->bt_bmap);
+               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;
        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_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)
 {
        }
 }
 
-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)
 {
        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)
 {
        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)
 {
        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)
 {
        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)
 {
 }
 
 
-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,
                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,
+               ret = nilfs_bmap_prepare_end_ptr(btree,
                                                 &path[level].bp_oldreq, dat);
                if (ret < 0)
                        goto err_out_child_node;
        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,
-                                        &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;
 
 
        /* 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;
                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_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;
        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:
        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;
 
-       btree = (struct nilfs_btree *)bmap;
        root = nilfs_btree_get_root(btree);
        switch (nilfs_btree_height(btree)) {
        case 2:
 }
 
 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;
 
 
        /* 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;
 
        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;
 
 
        /* 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,
                                      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;
 
        /* 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);
+               nilfs_btree_node_insert(btree, node, key, dreq->bpr_ptr, n);
                if (!buffer_dirty(bh))
                        nilfs_btnode_mark_dirty(bh);
-               if (!nilfs_bmap_dirty(bmap))
-                       nilfs_bmap_set_dirty(bmap);
+               if (!nilfs_bmap_dirty(btree))
+                       nilfs_bmap_set_dirty(btree);
 
                brelse(bh);
 
                nilfs_btree_node_init(btree, node, NILFS_BTREE_NODE_ROOT,
                                      2, 1, &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_insert(btree, node, key, dreq->bpr_ptr, n);
+               if (!nilfs_bmap_dirty(btree))
+                       nilfs_bmap_set_dirty(btree);
        }
 
-       if (NILFS_BMAP_USE_VBN(bmap))
+       if (NILFS_BMAP_USE_VBN(btree))
                nilfs_btree_set_target_v(btree, key, dreq->bpr_ptr);
 }
 
  * @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)
 {
                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 {
                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)
        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)
 {
                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,
        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)
 {
 
        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;
        }
                                 path[level].bp_newreq.bpr_ptr);
 }
 
-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)
 {
                               &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)
        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,
                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;
 
        get_bh(bh);
        return ret;
 }
 
-static int nilfs_btree_propagate(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;
 
        WARN_ON(!buffer_dirty(bh));
 
-       btree = (struct nilfs_btree *)bmap;
        path = nilfs_btree_alloc_path();
        if (path == NULL)
                return -ENOMEM;
                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;
        }
 
                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);
 
        return ret;
 }
 
-static int nilfs_btree_propagate_gc(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)
 {
                       "%s: invalid btree level: %d (key=%llu, ino=%lu, "
                       "blocknr=%llu)\n",
                       __func__, level, (unsigned long long)key,
-                      NILFS_BMAP_I(&btree->bt_bmap)->vfs_inode.i_ino,
+                      NILFS_BMAP_I(btree)->vfs_inode.i_ino,
                       (unsigned long long)bh->b_blocknr);
                return;
        }
        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;
                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,
                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;
        }
        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,
                                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;
 
        parent = nilfs_btree_get_node(btree, path, level + 1);
-       ptr = nilfs_btree_node_get_ptr(btree, parent,
-                                      path[level + 1].bp_index);
+       ptr = nilfs_btree_node_get_ptr(btree, parent, path[level + 1].bp_index);
        req.bpr_ptr = ptr;
        ret = nilfs_dat_prepare_start(dat, &req.bpr_req);
        if (ret < 0)
        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;
                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;
        }
 
                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);
 
        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)
        __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;
                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);
        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;
        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_free_path(path);