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>

1 files changed, 68 insertions, 26 deletions

diff --git a/fs/nilfs2/btree.c b/fs/nilfs2/btree.c
index 4669389bf686..1b5321c0bcac 100644
--- 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)