btrfs: use btrfs_read_node_slot in walk_down_reloc_tree

We do not need to call read_tree_block() here, simply use the
btrfs_read_node_slot helper.

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/relocation.c

@@ -1415,10 +1415,8 @@ static noinline_for_stack
 int walk_down_reloc_tree(struct btrfs_root *root, struct btrfs_path *path,
 			 int *level)
 {
-	struct btrfs_fs_info *fs_info = root->fs_info;
 	struct extent_buffer *eb = NULL;
 	int i;
-	u64 bytenr;
 	u64 ptr_gen = 0;
 	u64 last_snapshot;
 	u32 nritems;
@@ -1426,8 +1424,6 @@ int walk_down_reloc_tree(struct btrfs_root *root, struct btrfs_path *path,
 	last_snapshot = btrfs_root_last_snapshot(&root->root_item);
 
 	for (i = *level; i > 0; i--) {
-		struct btrfs_key first_key;
-
 		eb = path->nodes[i];
 		nritems = btrfs_header_nritems(eb);
 		while (path->slots[i] < nritems) {
@@ -1447,16 +1443,9 @@ int walk_down_reloc_tree(struct btrfs_root *root, struct btrfs_path *path,
 			return 0;
 		}
 
-		bytenr = btrfs_node_blockptr(eb, path->slots[i]);
-		btrfs_node_key_to_cpu(eb, &first_key, path->slots[i]);
-		eb = read_tree_block(fs_info, bytenr, ptr_gen, i - 1,
-				     &first_key);
-		if (IS_ERR(eb)) {
+		eb = btrfs_read_node_slot(eb, path->slots[i]);
+		if (IS_ERR(eb))
 			return PTR_ERR(eb);
-		} else if (!extent_buffer_uptodate(eb)) {
-			free_extent_buffer(eb);
-			return -EIO;
-		}
 		BUG_ON(btrfs_header_level(eb) != i - 1);
 		path->nodes[i - 1] = eb;
 		path->slots[i - 1] = 0;