On Tue, Aug 02, 2011 at 07:44:28PM +0800, Wu Fengguang wrote: > On Tue, Aug 02, 2011 at 12:52:42AM +0800, Christoph Hellwig wrote: > > wb_check_background_flush is indeed what we're hitting. > > That means s_umount is NOT held by another queued writeback work. Right. We already kind of knew that was ocurring because there's a remount,ro going on. > > > See the trace output using a patch inspired by Curt's below: > > > > # tracer: nop > > # > > # TASK-PID CPU# TIMESTAMP FUNCTION > > # | | | | | > > <...>-4279 [000] 113.034052: writeback_grab_super_failed: bdi 7:0: sb_dev 0:0 nr_pages=9223372036854775807 sync_mode=0 kupdate=0 range_cyclic=1 background=1 reason=wb_check_background_flush > > <...>-4279 [000] 113.034052: writeback_grab_super_failed: bdi 7:0: sb_dev 0:0 nr_pages=9223372036854775807 sync_mode=0 kupdate=0 range_cyclic=1 background=1 reason=wb_check_background_flush > > <...>-4279 [000] 113.034052: writeback_grab_super_failed: bdi 7:0: sb_dev 0:0 nr_pages=9223372036854775807 sync_mode=0 kupdate=0 range_cyclic=1 background=1 reason=wb_check_background_flush > > What's that bdi 7:0? And sb_dev=0:0, nr_pages=9223372036854775807=0x7fffffffffffffff. > > All are indicating some special bdi/inode. #define LOOP_MAJOR 7 It's a loop device. xfstests uses them quite a lot. Maybe it would be a good idea to run xfstests on an xfs filesystem in your regular writeback testing cycle to get decent coverage of this case? Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
