btrfs: add and use helper to determine if using bitmaps in free space tree

When adding and removing free space to the free space tree, we need to
lookup the respective block group's free info item in the free space tree,
check its flags for the BTRFS_FREE_SPACE_USING_BITMAPS bit and then
release the path.

Move these steps into a helper function and use it in both sites.
This will also help avoiding duplicate code in a subsequent change.

Reviewed-by: Boris Burkov <boris@bur.io>
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/free-space-tree.c

@@ -791,32 +791,40 @@ static int remove_free_space_extent(struct btrfs_trans_handle *trans,
 	return update_free_space_extent_count(trans, block_group, path, new_extents);
 }
 
+static int using_bitmaps(struct btrfs_block_group *bg, struct btrfs_path *path)
+{
+	struct btrfs_free_space_info *info;
+	u32 flags;
+
+	info = btrfs_search_free_space_info(NULL, bg, path, 0);
+	if (IS_ERR(info))
+		return PTR_ERR(info);
+	flags = btrfs_free_space_flags(path->nodes[0], info);
+	btrfs_release_path(path);
+
+	return (flags & BTRFS_FREE_SPACE_USING_BITMAPS) ? 1 : 0;
+}
+
 EXPORT_FOR_TESTS
 int __btrfs_remove_from_free_space_tree(struct btrfs_trans_handle *trans,
 					struct btrfs_block_group *block_group,
 					struct btrfs_path *path, u64 start, u64 size)
 {
-	struct btrfs_free_space_info *info;
-	u32 flags;
 	int ret;
 
 	ret = __add_block_group_free_space(trans, block_group, path);
 	if (ret)
 		return ret;
 
-	info = btrfs_search_free_space_info(NULL, block_group, path, 0);
-	if (IS_ERR(info))
-		return PTR_ERR(info);
-	flags = btrfs_free_space_flags(path->nodes[0], info);
-	btrfs_release_path(path);
+	ret = using_bitmaps(block_group, path);
+	if (ret < 0)
+		return ret;
 
-	if (flags & BTRFS_FREE_SPACE_USING_BITMAPS) {
+	if (ret)
 		return modify_free_space_bitmap(trans, block_group, path,
 						start, size, true);
-	} else {
-		return remove_free_space_extent(trans, block_group, path,
-						start, size);
-	}
+
+	return remove_free_space_extent(trans, block_group, path, start, size);
 }
 
 int btrfs_remove_from_free_space_tree(struct btrfs_trans_handle *trans,
@@ -984,27 +992,21 @@ int __btrfs_add_to_free_space_tree(struct btrfs_trans_handle *trans,
 				   struct btrfs_block_group *block_group,
 				   struct btrfs_path *path, u64 start, u64 size)
 {
-	struct btrfs_free_space_info *info;
-	u32 flags;
 	int ret;
 
 	ret = __add_block_group_free_space(trans, block_group, path);
 	if (ret)
 		return ret;
 
-	info = btrfs_search_free_space_info(NULL, block_group, path, 0);
-	if (IS_ERR(info))
-		return PTR_ERR(info);
-	flags = btrfs_free_space_flags(path->nodes[0], info);
-	btrfs_release_path(path);
+	ret = using_bitmaps(block_group, path);
+	if (ret < 0)
+		return ret;
 
-	if (flags & BTRFS_FREE_SPACE_USING_BITMAPS) {
+	if (ret)
 		return modify_free_space_bitmap(trans, block_group, path,
 						start, size, false);
-	} else {
-		return add_free_space_extent(trans, block_group, path, start,
-					     size);
-	}
+
+	return add_free_space_extent(trans, block_group, path, start, size);
 }
 
 int btrfs_add_to_free_space_tree(struct btrfs_trans_handle *trans,