nilfs2: add btree get block function with readahead option

This adds __nilfs_btree_get_block() function that can issue a series
of read-ahead requests for sibling btree nodes.

This read-ahead needs parent node block, so nilfs_btree_readahead_info
structure is added to pass the information that
__nilfs_btree_get_block() needs.

This also replaces the previous nilfs_btree_get_block() implementation
with a wrapper function of __nilfs_btree_get_block().

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

diff --git a/fs/nilfs2/btree.c b/fs/nilfs2/btree.c
index 4669389bf6865680aa15ab0946359577c01c2996..1b5321c0bcac86866d1f81eb555b46af26abac45 100644 (file)
--- a/fs/nilfs2/btree.c
+++ b/fs/nilfs2/btree.c
@@ -66,32 +66,6 @@ static void nilfs_btree_free_path(struct nilfs_btree_path *path)
 /*
  * B-tree node operations
  */
-static int nilfs_btree_get_block(const struct nilfs_bmap *btree, __u64 ptr,
-                                struct buffer_head **bhp)
-{
-       struct address_space *btnc = &NILFS_BMAP_I(btree)->i_btnode_cache;
-       struct buffer_head *bh;
-       sector_t pbn = 0;
-       int err;
-
-       err = nilfs_btnode_submit_block(btnc, ptr, pbn, READ, bhp, &pbn);
-       if (err)
-               return err == -EEXIST ? 0 : err;
-
-       bh = *bhp;
-       wait_on_buffer(bh);
-       if (!buffer_uptodate(bh)) {
-               brelse(bh);
-               return -EIO;
-       }
-       if (nilfs_btree_broken_node_block(bh)) {
-               clear_buffer_uptodate(bh);
-               brelse(bh);
-               return -EINVAL;
-       }
-       return 0;
-}
-
 static int nilfs_btree_get_new_block(const struct nilfs_bmap *btree,
                                     __u64 ptr, struct buffer_head **bhp)
 {
@@ -452,6 +426,74 @@ nilfs_btree_bad_node(struct nilfs_btree_node *node, int level)
        return 0;
 }
 
+struct nilfs_btree_readahead_info {
+       struct nilfs_btree_node *node;  /* parent node */
+       int max_ra_blocks;              /* max nof blocks to read ahead */
+       int index;                      /* current index on the parent node */
+       int ncmax;                      /* nof children in the parent node */
+};
+
+static int __nilfs_btree_get_block(const struct nilfs_bmap *btree, __u64 ptr,
+                                  struct buffer_head **bhp,
+                                  const struct nilfs_btree_readahead_info *ra)
+{
+       struct address_space *btnc = &NILFS_BMAP_I(btree)->i_btnode_cache;
+       struct buffer_head *bh, *ra_bh;
+       sector_t submit_ptr = 0;
+       int ret;
+
+       ret = nilfs_btnode_submit_block(btnc, ptr, 0, READ, &bh, &submit_ptr);
+       if (ret) {
+               if (ret != -EEXIST)
+                       return ret;
+               goto out_check;
+       }
+
+       if (ra) {
+               int i, n;
+               __u64 ptr2;
+
+               /* read ahead sibling nodes */
+               for (n = ra->max_ra_blocks, i = ra->index + 1;
+                    n > 0 && i < ra->ncmax; n--, i++) {
+                       ptr2 = nilfs_btree_node_get_ptr(ra->node, i, ra->ncmax);
+
+                       ret = nilfs_btnode_submit_block(btnc, ptr2, 0, READA,
+                                                       &ra_bh, &submit_ptr);
+                       if (likely(!ret || ret == -EEXIST))
+                               brelse(ra_bh);
+                       else if (ret != -EBUSY)
+                               break;
+                       if (!buffer_locked(bh))
+                               goto out_no_wait;
+               }
+       }
+
+       wait_on_buffer(bh);
+
+ out_no_wait:
+       if (!buffer_uptodate(bh)) {
+               brelse(bh);
+               return -EIO;
+       }
+
+ out_check:
+       if (nilfs_btree_broken_node_block(bh)) {
+               clear_buffer_uptodate(bh);
+               brelse(bh);
+               return -EINVAL;
+       }
+
+       *bhp = bh;
+       return 0;
+}
+
+static int nilfs_btree_get_block(const struct nilfs_bmap *btree, __u64 ptr,
+                                  struct buffer_head **bhp)
+{
+       return __nilfs_btree_get_block(btree, ptr, bhp, NULL);
+}
+
 static int nilfs_btree_do_lookup(const struct nilfs_bmap *btree,
                                 struct nilfs_btree_path *path,
                                 __u64 key, __u64 *ptrp, int minlevel)