btrfs: qgroup: Fix dead judgement on qgroup_rescan_leaf() return value.

Old qgroup_rescan_leaf() comment indicates ret == 2 as complete and
cleared INCONSISTENT flag.

This is not true since it will never return 2, and inside it no codes
will clear INCONSISTENT flag.
The flag clearance is done in btrfs_qgroup_rescan_work().
This caused the bug that INCONSISTENT flag is never cleared.

So change the comment and fix the dead judgment.
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>

fs/btrfs/qgroup.c

@@ -2560,7 +2560,7 @@ void assert_qgroups_uptodate(struct btrfs_trans_handle *trans)
 
 /*
  * returns < 0 on error, 0 when more leafs are to be scanned.
- * returns 1 when done, 2 when done and FLAG_INCONSISTENT was cleared.
+ * returns 1 when done.
  */
 static int
 qgroup_rescan_leaf(struct btrfs_fs_info *fs_info, struct btrfs_path *path,
@@ -2707,7 +2707,7 @@ static void btrfs_qgroup_rescan_worker(struct btrfs_work *work)
 	mutex_lock(&fs_info->qgroup_rescan_lock);
 	fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_RESCAN;
 
-	if (err == 2 &&
+	if (err > 0 &&
 	    fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT) {
 		fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
 	} else if (err < 0) {
@@ -2717,7 +2717,7 @@ static void btrfs_qgroup_rescan_worker(struct btrfs_work *work)
 
 	if (err >= 0) {
 		btrfs_info(fs_info, "qgroup scan completed%s",
-			err == 2 ? " (inconsistency flag cleared)" : "");
+			err > 0 ? " (inconsistency flag cleared)" : "");
 	} else {
 		btrfs_err(fs_info, "qgroup scan failed with %d", err);
 	}