diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 22ba2b4505b3..00d4c4184e76 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -160,7 +160,7 @@ enum {
  */
 struct btrfs_qgroup_swapped_blocks {
 	spinlock_t lock;
-	/* RM_EMPTY_ROOT() of above blocks[] */
+	/* True if any of the rbtrees in the blocks array below is not empty. */
 	bool swapped;
 	struct rb_root blocks[BTRFS_MAX_LEVEL];
 };
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 46de0a5e80d5..798f21608de5 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -4913,7 +4913,7 @@ int btrfs_qgroup_trace_subtree_after_cow(struct btrfs_trans_handle *trans,
 	/* Found one, remove it from @blocks first and update blocks->swapped */
 	rb_erase(&block->node, &blocks->blocks[level]);
 	for (i = 0; i < BTRFS_MAX_LEVEL; i++) {
-		if (RB_EMPTY_ROOT(&blocks->blocks[i])) {
+		if (!RB_EMPTY_ROOT(&blocks->blocks[i])) {
 			swapped = true;
 			break;
 		}