nilfs2: reduce repetitive calculation of max number of child nodes

The current btree implementation repeats the same calculation on the
maximum number of child nodes.  This is because a few low level
routines use the calculation for index addressing in a btree node
block.

This reduces the calculation by explicitly passing the maximum number
of child nodes (ncmax) through their argument.

This changes parameter passing of the following functions:

 - nilfs_btree_node_dptrs
 - nilfs_btree_node_get_ptr
 - nilfs_btree_node_set_ptr
 - nilfs_btree_node_init
 - nilfs_btree_node_move_left
 - nilfs_btree_node_move_right
 - nilfs_btree_node_insert
 - nilfs_btree_node_delete, and
 - nilfs_btree_get_node

The following functions are removed:

 - nilfs_btree_node_nchildren_min
 - nilfs_btree_node_nchildren_max

Most middle level btree operations are rewritten to pass a proper
ncmax value depending on whether each occurrence of node is "root" or
not.

A constant NILFS_BTREE_ROOT_NCHILDREN_MAX is used for the root node,
whereas nilfs_btree_nchildren_per_block() function is used for
non-root nodes.  If a node could be either root or a non-root node, an
output argument of nilfs_btree_get_node() is used to set up ncmax.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

1 files changed, 182 insertions, 157 deletions

diff --git a/fs/nilfs2/btree.c b/fs/nilfs2/btree.c
index c0266f7f0b26..829e145f1353 100644
--- a/fs/nilfs2/btree.c
+++ b/fs/nilfs2/btree.c
@@ -152,22 +152,9 @@ static inline int nilfs_btree_node_size(const struct nilfs_bmap *btree)
         return 1 << btree->b_inode->i_blkbits;
 }
 
-static inline int
-nilfs_btree_node_nchildren_min(const struct nilfs_btree_node *node,
-                               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));
-}
-
-static inline int
-nilfs_btree_node_nchildren_max(const struct nilfs_btree_node *node,
-                               const struct nilfs_bmap *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 NILFS_BTREE_NODE_NCHILDREN_MAX(nilfs_btree_node_size(btree));
 }
 
 static inline __le64 *
@@ -179,11 +166,9 @@ nilfs_btree_node_dkeys(const struct nilfs_btree_node *node)
 }
 
 static inline __le64 *
-nilfs_btree_node_dptrs(const struct nilfs_btree_node *node,
-                       const struct nilfs_bmap *btree)
+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
@@ -199,22 +184,21 @@ nilfs_btree_node_set_key(struct nilfs_btree_node *node, int index, __u64 key)
 }
 
 static inline __u64
-nilfs_btree_node_get_ptr(const struct nilfs_bmap *btree,
-                         const struct nilfs_btree_node *node, int index)
+nilfs_btree_node_get_ptr(const struct nilfs_btree_node *node, int index,
+                         int ncmax)
 {
-        return le64_to_cpu(*(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_bmap *btree,
-                         struct nilfs_btree_node *node, int index, __u64 ptr)
+nilfs_btree_node_set_ptr(struct nilfs_btree_node *node, int index, __u64 ptr,
+                         int ncmax)
 {
-        *(nilfs_btree_node_dptrs(node, btree) + index) = cpu_to_le64(ptr);
+        *(nilfs_btree_node_dptrs(node, ncmax) + index) = cpu_to_le64(ptr);
 }
 
-static void nilfs_btree_node_init(struct nilfs_bmap *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;
@@ -226,7 +210,7 @@ static void nilfs_btree_node_init(struct nilfs_bmap *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] = cpu_to_le64(keys[i]);
                 dptrs[i] = cpu_to_le64(ptrs[i]);
@@ -234,21 +218,20 @@ static void nilfs_btree_node_init(struct nilfs_bmap *btree,
 }
 
 /* Assume the buffer heads corresponding to left and right are locked. */
-static void nilfs_btree_node_move_left(struct nilfs_bmap *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));
@@ -263,21 +246,20 @@ static void nilfs_btree_node_move_left(struct nilfs_bmap *btree,
 }
 
 /* Assume that the buffer heads corresponding to left and right are locked. */
-static void nilfs_btree_node_move_right(struct nilfs_bmap *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));
@@ -292,16 +274,15 @@ static void nilfs_btree_node_move_right(struct nilfs_bmap *btree,
 }
 
 /* Assume that the buffer head corresponding to node is locked. */
-static void nilfs_btree_node_insert(struct nilfs_bmap *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,
@@ -316,9 +297,8 @@ static void nilfs_btree_node_insert(struct nilfs_bmap *btree,
 }
 
 /* Assume that the buffer head corresponding to node is locked. */
-static void nilfs_btree_node_delete(struct nilfs_bmap *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;
@@ -327,7 +307,7 @@ static void nilfs_btree_node_delete(struct nilfs_bmap *btree,
         int nchildren;
 
         dkeys = nilfs_btree_node_dkeys(node);
-        dptrs = nilfs_btree_node_dptrs(node, btree);
+        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);
@@ -445,14 +425,21 @@ 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 *
+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
@@ -481,11 +468,12 @@ static int nilfs_btree_do_lookup(const struct nilfs_bmap *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;
 
-        ncmax = NILFS_BTREE_NODE_NCHILDREN_MAX(nilfs_btree_node_size(btree));
+        ncmax = nilfs_btree_nchildren_per_block(btree);
 
         for (level--; level >= minlevel; level--) {
                 ret = nilfs_btree_get_block(btree, ptr, &path[level].bp_bh);
@@ -499,7 +487,7 @@ static int nilfs_btree_do_lookup(const struct nilfs_bmap *btree,
                 else
                         index = 0;
                 if (index < ncmax) {
-                        ptr = nilfs_btree_node_get_ptr(btree, node, index);
+                        ptr = nilfs_btree_node_get_ptr(node, index, ncmax);
                 } else {
                         WARN_ON(found || level != NILFS_BTREE_LEVEL_NODE_MIN);
                         /* insert */
@@ -522,16 +510,18 @@ static int nilfs_btree_do_lookup_last(const struct nilfs_bmap *btree,
 {
         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);
@@ -541,7 +531,7 @@ static int nilfs_btree_do_lookup_last(const struct nilfs_bmap *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;
         }
 
@@ -579,7 +569,7 @@ static int nilfs_btree_lookup_contig(const struct nilfs_bmap *btree,
         __u64 ptr, ptr2;
         sector_t blocknr;
         int level = NILFS_BTREE_LEVEL_NODE_MIN;
-        int ret, cnt, index, maxlevel;
+        int ret, cnt, index, maxlevel, ncmax;
 
         path = nilfs_btree_alloc_path();
         if (path == NULL)
@@ -601,14 +591,14 @@ static int nilfs_btree_lookup_contig(const struct nilfs_bmap *btree,
                 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)
@@ -624,12 +614,12 @@ static int nilfs_btree_lookup_contig(const struct nilfs_bmap *btree,
                         break;
 
                 /* look-up right sibling node */
-                node = nilfs_btree_get_node(btree, path, level + 1);
+                node = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
                 index = path[level + 1].bp_index + 1;
                 if (index >= nilfs_btree_node_get_nchildren(node) ||
                     nilfs_btree_node_get_key(node, index) != key + cnt)
                         break;
-                ptr2 = nilfs_btree_node_get_ptr(btree, node, index);
+                ptr2 = nilfs_btree_node_get_ptr(node, index, ncmax);
                 path[level + 1].bp_index = index;
 
                 brelse(path[level].bp_bh);
@@ -638,6 +628,7 @@ static int nilfs_btree_lookup_contig(const struct nilfs_bmap *btree,
                 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;
         }
@@ -676,11 +667,13 @@ static void nilfs_btree_do_insert(struct nilfs_bmap *btree,
                                   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);
 
@@ -690,8 +683,9 @@ static void nilfs_btree_do_insert(struct nilfs_bmap *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);
         }
 }
 
@@ -700,12 +694,13 @@ static void nilfs_btree_carry_left(struct nilfs_bmap *btree,
                                    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;
@@ -715,7 +710,7 @@ static void nilfs_btree_carry_left(struct nilfs_bmap *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);
@@ -745,12 +740,13 @@ static void nilfs_btree_carry_right(struct nilfs_bmap *btree,
                                     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;
@@ -760,7 +756,7 @@ static void nilfs_btree_carry_right(struct nilfs_bmap *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);
@@ -793,11 +789,12 @@ static void nilfs_btree_split(struct nilfs_bmap *btree,
         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;
@@ -806,7 +803,7 @@ static void nilfs_btree_split(struct nilfs_bmap *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);
@@ -818,8 +815,8 @@ static void nilfs_btree_split(struct nilfs_bmap *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;
@@ -845,14 +842,16 @@ static void nilfs_btree_grow(struct nilfs_bmap *btree,
                              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))
@@ -871,7 +870,7 @@ 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;
@@ -879,17 +878,18 @@ static __u64 nilfs_btree_find_near(const struct nilfs_bmap *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;
@@ -923,7 +923,7 @@ static int nilfs_btree_prepare_insert(struct nilfs_bmap *btree,
         struct buffer_head *bh;
         struct nilfs_btree_node *node, *parent, *sib;
         __u64 sibptr;
-        int pindex, level, ncmax, ret;
+        int pindex, level, ncmax, ncblk, ret;
         struct inode *dat = NULL;
 
         stats->bs_nblocks = 0;
@@ -940,54 +940,55 @@ static int nilfs_btree_prepare_insert(struct nilfs_bmap *btree,
         if (ret < 0)
                 goto err_out_data;
 
-        ncmax = NILFS_BTREE_NODE_NCHILDREN_MAX(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);
-                if (nilfs_btree_node_get_nchildren(node) < ncmax) {
+                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) < ncmax) {
+                        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) < ncmax) {
+                        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 */
@@ -1005,9 +1006,8 @@ static int nilfs_btree_prepare_insert(struct nilfs_bmap *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;
         }
@@ -1031,8 +1031,8 @@ static int nilfs_btree_prepare_insert(struct nilfs_bmap *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;
 
@@ -1122,11 +1122,13 @@ static void nilfs_btree_do_delete(struct nilfs_bmap *btree,
                                   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)
@@ -1134,8 +1136,9 @@ static void nilfs_btree_do_delete(struct nilfs_bmap *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);
         }
 }
 
@@ -1144,7 +1147,7 @@ static void nilfs_btree_borrow_left(struct nilfs_bmap *btree,
                                     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);
 
@@ -1152,10 +1155,11 @@ static void nilfs_btree_borrow_left(struct nilfs_bmap *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);
@@ -1175,7 +1179,7 @@ static void nilfs_btree_borrow_right(struct nilfs_bmap *btree,
                                      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);
 
@@ -1183,10 +1187,11 @@ static void nilfs_btree_borrow_right(struct nilfs_bmap *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);
@@ -1207,16 +1212,17 @@ static void nilfs_btree_concat_left(struct nilfs_bmap *btree,
                                     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);
@@ -1232,16 +1238,17 @@ static void nilfs_btree_concat_right(struct nilfs_bmap *btree,
                                      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);
@@ -1256,17 +1263,20 @@ static void nilfs_btree_shrink(struct nilfs_bmap *btree,
                                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;
@@ -1282,19 +1292,20 @@ static int nilfs_btree_prepare_delete(struct nilfs_bmap *btree,
         struct buffer_head *bh;
         struct nilfs_btree_node *node, *parent, *sib;
         __u64 sibptr;
-        int pindex, level, ncmin, 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);
+                        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)
@@ -1306,13 +1317,13 @@ static int nilfs_btree_prepare_delete(struct nilfs_bmap *btree,
                         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;
@@ -1331,8 +1342,8 @@ static int nilfs_btree_prepare_delete(struct nilfs_bmap *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;
@@ -1368,7 +1379,8 @@ static int nilfs_btree_prepare_delete(struct nilfs_bmap *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, &path[level].bp_oldreq, dat);
         if (ret < 0)
@@ -1476,7 +1488,8 @@ static int nilfs_btree_check_delete(struct nilfs_bmap *btree, __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;
@@ -1504,22 +1517,25 @@ static int nilfs_btree_gather_data(struct nilfs_bmap *btree,
         __le64 *dkeys;
         __le64 *dptrs;
         __u64 ptr;
-        int nchildren, i, ret;
+        int nchildren, ncmax, i, ret;
 
         root = nilfs_btree_get_root(btree);
         switch (nilfs_btree_height(btree)) {
         case 2:
                 bh = NULL;
                 node = root;
+                ncmax = NILFS_BTREE_ROOT_NCHILDREN_MAX;
                 break;
         case 3:
                 nchildren = nilfs_btree_node_get_nchildren(root);
                 WARN_ON(nchildren > 1);
-                ptr = nilfs_btree_node_get_ptr(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;
@@ -1530,7 +1546,7 @@ static int nilfs_btree_gather_data(struct nilfs_bmap *btree,
         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] = le64_to_cpu(dkeys[i]);
                 ptrs[i] = le64_to_cpu(dptrs[i]);
@@ -1607,6 +1623,7 @@ nilfs_btree_commit_convert_and_insert(struct nilfs_bmap *btree,
         struct nilfs_btree_node *node;
         struct inode *dat;
         __u64 tmpptr;
+        int ncblk;
 
         /* free resources */
         if (btree->b_ops->bop_clear != NULL)
@@ -1624,8 +1641,9 @@ nilfs_btree_commit_convert_and_insert(struct nilfs_bmap *btree,
 
                 /* 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(btree))
@@ -1636,16 +1654,19 @@ nilfs_btree_commit_convert_and_insert(struct nilfs_bmap *btree,
                 /* 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(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);
+                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);
         }
@@ -1712,12 +1733,12 @@ static int nilfs_btree_prepare_update_v(struct nilfs_bmap *btree,
                                         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);
@@ -1747,6 +1768,7 @@ static void nilfs_btree_commit_update_v(struct nilfs_bmap *btree,
                                         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,
@@ -1760,9 +1782,9 @@ static void nilfs_btree_commit_update_v(struct nilfs_bmap *btree,
         }
         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_bmap *btree,
@@ -1835,6 +1857,7 @@ static int nilfs_btree_propagate_v(struct nilfs_bmap *btree,
         struct nilfs_btree_node *parent;
         struct inode *dat = nilfs_bmap_get_dat(btree);
         __u64 ptr;
+        int ncmax;
 
         get_bh(bh);
         path[level].bp_bh = bh;
@@ -1844,9 +1867,10 @@ static int nilfs_btree_propagate_v(struct nilfs_bmap *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;
@@ -1990,11 +2014,11 @@ static int nilfs_btree_assign_p(struct nilfs_bmap *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;
@@ -2010,8 +2034,8 @@ static int nilfs_btree_assign_p(struct nilfs_bmap *btree,
                 *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 */
@@ -2033,10 +2057,11 @@ static int nilfs_btree_assign_v(struct nilfs_bmap *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)