btrfs: mark as unlikely not uptodate extent buffer checks when navigating btrees

We expect that after attempting to read an extent buffer we had no errors
therefore the extent buffer is up to date, so mark the checks for a not up
to date extent buffer as unlikely and allow the compiler to pontentially
generate better code.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Author: fdmanana

fs/btrfs/ctree.c

@@ -844,7 +844,7 @@ struct extent_buffer *btrfs_read_node_slot(struct extent_buffer *parent,
 			     &check);
 	if (IS_ERR(eb))
 		return eb;
-	if (!extent_buffer_uptodate(eb)) {
+	if (unlikely(!extent_buffer_uptodate(eb))) {
 		free_extent_buffer(eb);
 		return ERR_PTR(-EIO);
 	}
@@ -1571,7 +1571,7 @@ read_block_for_search(struct btrfs_root *root, struct btrfs_path *p,
 	 * and give up so that our caller doesn't loop forever
 	 * on our EAGAINs.
 	 */
-	if (!extent_buffer_uptodate(tmp)) {
+	if (unlikely(!extent_buffer_uptodate(tmp))) {
 		ret = -EIO;
 		goto out;
 	}
@@ -1752,7 +1752,7 @@ static struct extent_buffer *btrfs_search_slot_get_root(struct btrfs_root *root,
 	 * The root may have failed to write out at some point, and thus is no
 	 * longer valid, return an error in this case.
 	 */
-	if (!extent_buffer_uptodate(b)) {
+	if (unlikely(!extent_buffer_uptodate(b))) {
 		if (root_lock)
 			btrfs_tree_unlock_rw(b, root_lock);
 		free_extent_buffer(b);
@@ -2260,7 +2260,7 @@ int btrfs_search_old_slot(struct btrfs_root *root, const struct btrfs_key *key,
 
 again:
 	b = btrfs_get_old_root(root, time_seq);
-	if (!b) {
+	if (unlikely(!b)) {
 		ret = -EIO;
 		goto done;
 	}