btrfs: reloc: move error handling of build_backref_tree() to backref.c

The error cleanup will be extracted as a new function,
btrfs_backref_error_cleanup(), and moved to backref.c and exported for
later usage.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/backref.c

@@ -3063,3 +3063,57 @@ int btrfs_backref_finish_upper_links(struct btrfs_backref_cache *cache,
 	}
 	return 0;
 }
+
+void btrfs_backref_error_cleanup(struct btrfs_backref_cache *cache,
+				 struct btrfs_backref_node *node)
+{
+	struct btrfs_backref_node *lower;
+	struct btrfs_backref_node *upper;
+	struct btrfs_backref_edge *edge;
+
+	while (!list_empty(&cache->useless_node)) {
+		lower = list_first_entry(&cache->useless_node,
+				   struct btrfs_backref_node, list);
+		list_del_init(&lower->list);
+	}
+	while (!list_empty(&cache->pending_edge)) {
+		edge = list_first_entry(&cache->pending_edge,
+				struct btrfs_backref_edge, list[UPPER]);
+		list_del(&edge->list[UPPER]);
+		list_del(&edge->list[LOWER]);
+		lower = edge->node[LOWER];
+		upper = edge->node[UPPER];
+		btrfs_backref_free_edge(cache, edge);
+
+		/*
+		 * Lower is no longer linked to any upper backref nodes and
+		 * isn't in the cache, we can free it ourselves.
+		 */
+		if (list_empty(&lower->upper) &&
+		    RB_EMPTY_NODE(&lower->rb_node))
+			list_add(&lower->list, &cache->useless_node);
+
+		if (!RB_EMPTY_NODE(&upper->rb_node))
+			continue;
+
+		/* Add this guy's upper edges to the list to process */
+		list_for_each_entry(edge, &upper->upper, list[LOWER])
+			list_add_tail(&edge->list[UPPER],
+				      &cache->pending_edge);
+		if (list_empty(&upper->upper))
+			list_add(&upper->list, &cache->useless_node);
+	}
+
+	while (!list_empty(&cache->useless_node)) {
+		lower = list_first_entry(&cache->useless_node,
+				   struct btrfs_backref_node, list);
+		list_del_init(&lower->list);
+		if (lower == node)
+			node = NULL;
+		btrfs_backref_free_node(cache, lower);
+	}
+
+	btrfs_backref_cleanup_node(cache, node);
+	ASSERT(list_empty(&cache->useless_node) &&
+	       list_empty(&cache->pending_edge));
+}

fs/btrfs/backref.h

@@ -372,4 +372,7 @@ int btrfs_backref_add_tree_node(struct btrfs_backref_cache *cache,
 int btrfs_backref_finish_upper_links(struct btrfs_backref_cache *cache,
 				     struct btrfs_backref_node *start);
 
+void btrfs_backref_error_cleanup(struct btrfs_backref_cache *cache,
+				 struct btrfs_backref_node *node);
+
 #endif

fs/btrfs/relocation.c

@@ -474,8 +474,6 @@ static noinline_for_stack struct btrfs_backref_node *build_backref_tree(
 	/* For searching parent of TREE_BLOCK_REF */
 	struct btrfs_path *path;
 	struct btrfs_backref_node *cur;
-	struct btrfs_backref_node *upper;
-	struct btrfs_backref_node *lower;
 	struct btrfs_backref_node *node = NULL;
 	struct btrfs_backref_edge *edge;
 	int ret;
@@ -532,51 +530,7 @@ static noinline_for_stack struct btrfs_backref_node *build_backref_tree(
 	btrfs_backref_iter_free(iter);
 	btrfs_free_path(path);
 	if (err) {
-		while (!list_empty(&cache->useless_node)) {
-			lower = list_first_entry(&cache->useless_node,
-					   struct btrfs_backref_node, list);
-			list_del_init(&lower->list);
-		}
-		while (!list_empty(&cache->pending_edge)) {
-			edge = list_first_entry(&cache->pending_edge,
-					struct btrfs_backref_edge, list[UPPER]);
-			list_del(&edge->list[UPPER]);
-			list_del(&edge->list[LOWER]);
-			lower = edge->node[LOWER];
-			upper = edge->node[UPPER];
-			btrfs_backref_free_edge(cache, edge);
-
-			/*
-			 * Lower is no longer linked to any upper backref nodes
-			 * and isn't in the cache, we can free it ourselves.
-			 */
-			if (list_empty(&lower->upper) &&
-			    RB_EMPTY_NODE(&lower->rb_node))
-				list_add(&lower->list, &cache->useless_node);
-
-			if (!RB_EMPTY_NODE(&upper->rb_node))
-				continue;
-
-			/* Add this guy's upper edges to the list to process */
-			list_for_each_entry(edge, &upper->upper, list[LOWER])
-				list_add_tail(&edge->list[UPPER],
-					      &cache->pending_edge);
-			if (list_empty(&upper->upper))
-				list_add(&upper->list, &cache->useless_node);
-		}
-
-		while (!list_empty(&cache->useless_node)) {
-			lower = list_first_entry(&cache->useless_node,
-					   struct btrfs_backref_node, list);
-			list_del_init(&lower->list);
-			if (lower == node)
-				node = NULL;
-			btrfs_backref_free_node(cache, lower);
-		}
-
-		btrfs_backref_cleanup_node(cache, node);
-		ASSERT(list_empty(&cache->useless_node) &&
-		       list_empty(&cache->pending_edge));
+		btrfs_backref_error_cleanup(cache, node);
 		return ERR_PTR(err);
 	}
 	ASSERT(!node || !node->detached);