btrfs: add cond_resched to btrfs_qgroup_trace_leaf_items

On an uncontended system, we can end up hitting soft lockups while
doing replace_path.  At the core, and frequently called is
btrfs_qgroup_trace_leaf_items, so it makes sense to add a cond_resched
there.
Signed-off-by: NJeff Mahoney <jeffm@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/qgroup.c

@@ -1559,6 +1559,7 @@ int btrfs_qgroup_trace_leaf_items(struct btrfs_trans_handle *trans,
 		if (ret)
 			return ret;
 	}
+	cond_resched();
 	return 0;
 }