[PATCH v3 03/15] btrfs: use btrfs_read_extent_buffer in do_walk_down

[Josef Bacik <josef@toxicpanda.com>]

Currently if our extent buffer isn't uptodate we will drop the lock,
free it, and then call read_tree_block() for the bytenr.  This is
inefficient, we already have the extent buffer, we can simply call
btrfs_read_extent_buffer().

Collapse these two cases down into one if statement, if we are not
uptodate we can drop the lock, trigger readahead, and do the read using
btrfs_read_extent_buffer(), and carry on.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/extent-tree.c | 15 ++++-----------
 1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index d020ee1a6473..fa59a0b5bc2d 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -5507,22 +5507,15 @@ static noinline int do_walk_down(struct btrfs_trans_handle *trans,
 
 	if (!btrfs_buffer_uptodate(next, generation, 0)) {
 		btrfs_tree_unlock(next);
-		free_extent_buffer(next);
-		next = NULL;
-		*lookup_info = 1;
-	}
-
-	if (!next) {
 		if (level == 1)
 			reada_walk_down(trans, root, wc, path);
-		next = read_tree_block(fs_info, bytenr, &check);
-		if (IS_ERR(next)) {
-			return PTR_ERR(next);
-		} else if (!extent_buffer_uptodate(next)) {
+		ret = btrfs_read_extent_buffer(next, &check);
+		if (ret) {
 			free_extent_buffer(next);
-			return -EIO;
+			return ret;
 		}
 		btrfs_tree_lock(next);
+		*lookup_info = 1;
 	}
 
 	level--;
-- 
2.43.0