btrfs: rename err and ret to ret in build_backref_tree()

Code style fix in the function build_backref_tree().  Drop the ret
initialization 0, as we don't need it.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/relocation.c

@@ -473,20 +473,19 @@ static noinline_for_stack struct btrfs_backref_node *build_backref_tree(
 	struct btrfs_backref_node *node = NULL;
 	struct btrfs_backref_edge *edge;
 	int ret;
-	int err = 0;
 
 	iter = btrfs_backref_iter_alloc(rc->extent_root->fs_info);
 	if (!iter)
 		return ERR_PTR(-ENOMEM);
 	path = btrfs_alloc_path();
 	if (!path) {
-		err = -ENOMEM;
+		ret = -ENOMEM;
 		goto out;
 	}
 
 	node = btrfs_backref_alloc_node(cache, bytenr, level);
 	if (!node) {
-		err = -ENOMEM;
+		ret = -ENOMEM;
 		goto out;
 	}
 
@@ -497,10 +496,9 @@ static noinline_for_stack struct btrfs_backref_node *build_backref_tree(
 	do {
 		ret = btrfs_backref_add_tree_node(trans, cache, path, iter,
 						  node_key, cur);
-		if (ret < 0) {
-			err = ret;
+		if (ret < 0)
 			goto out;
-		}
+
 		edge = list_first_entry_or_null(&cache->pending_edge,
 				struct btrfs_backref_edge, list[UPPER]);
 		/*
@@ -515,20 +513,18 @@ static noinline_for_stack struct btrfs_backref_node *build_backref_tree(
 
 	/* Finish the upper linkage of newly added edges/nodes */
 	ret = btrfs_backref_finish_upper_links(cache, node);
-	if (ret < 0) {
-		err = ret;
+	if (ret < 0)
 		goto out;
-	}
 
 	if (handle_useless_nodes(rc, node))
 		node = NULL;
 out:
 	btrfs_free_path(iter->path);
 	kfree(iter);
 	btrfs_free_path(path);
-	if (err) {
+	if (ret) {
 		btrfs_backref_error_cleanup(cache, node);
-		return ERR_PTR(err);
+		return ERR_PTR(ret);
 	}
 	ASSERT(!node || !node->detached);
 	ASSERT(list_empty(&cache->useless_node) &&