Re: deadlock with latest xfs

Dave Chinner wrote:

On Fri, Oct 24, 2008 at 01:08:55PM +1000, Lachlan McIlroy wrote:

quoted

Christoph Hellwig wrote:

quoted

On Thu, Oct 23, 2008 at 07:17:30PM +1000, Lachlan McIlroy wrote:

quoted

another problem with latest xfs

Is this with the 2.6.27-based ptools/cvs tree or with the 2.6.28 based
git tree?  It does looks more like a VM issue than a XFS issue to me.

It's with the 2.6.27-rc8 based ptools tree.  Prior to checking
in these patches:

Can't lock inodes in radix tree preload region
stop using xfs_itobp in xfs_bulkstat
free partially initialized inodes using destroy_inode

I was able to stress a system for about 4 hours before it ran out
of memory.  Now I hit the deadlock within a few minutes.  I need
to roll back to find which patch changed the behaviour.

Ok, I think I've found the regression - it's introduced by the AIL
cursor modifications. The patch below has been running for 15
minutes now on my UML box that would have hung in a couple of
minutes otherwise.

Yep, looks good here too.  My test system has been up at least an hour
and still chugging.

FYI, the way I found this was:

	- put a breakpoint on xfs_create() once the fs hung
	- `touch /mnt/xfs2/fred` to trigger the break point.
	- look at:
		- mp->m_ail->xa_target
		- mp->m_ail->xa_ail.next->li_lsn
		- mp->m_log->l_tail_lsn
	  which indicated the push target was way ahead the
	  tail of the log, so AIL pushing was obviously not
	  happening otherwise we'd be making progress.
	- added breakpoint on xfsaild_push() and continued
	- xfsaild_push() bp triggered, looked at *last_lsn
	  and found it way behind the tail of the log (like
	  3 cycle behind), which meant that would return
	  NULL instead of the first object and AIL pushing
	  would abort. Confirmed with single stepping.

Cheers,

Dave.