Date:	Thu, 07 Jun 2007 14:59:58 +0100
From:	David Greaves <david@...eaves.com>
To:	David Chinner <dgc@....com>
Cc:	Tejun Heo <htejun@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, xfs@....sgi.com,
	"'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>,
	linux-pm <linux-pm@...ts.osdl.org>, Neil Brown <neilb@...e.de>
Subject: Re: 2.6.22-rc3 hibernate(?) fails totally - regression (xfs on raid6)

David Chinner wrote:
> On Thu, Jun 07, 2007 at 11:30:05AM +0100, David Greaves wrote:
>> Tejun Heo wrote:
>>> Hello,
>>>
>>> David Greaves wrote:
>>>> Just to be clear. This problem is where my system won't resume after s2d
>>>> unless I umount my xfs over raid6 filesystem.
>>> This is really weird.  I don't see how xfs mount can affect this at all.
>> Indeed.
>> It does :)
> 
> Ok, so lets determine if it really is XFS.
Seems like a good next step...

> Does the lockup happen with a
> different filesystem on the md device? Or if you can't test that, does
> any other XFS filesystem you have show the same problem?
It's a rather full 1.2Tb raid6 array - can't reformat it - sorry :)
I only noticed the problem when I umounted the fs during tests to prevent 
corruption - and it worked. I'm doing a sync each time it hibernates (see below) 
and a couple of paranoia xfs_repairs haven't shown any problems.

I do have another xfs filesystem on /dev/hdb2 (mentioned when I noticed the 
md/XFS correlation). It doesn't seem to have/cause any problems.

> If it is xfs that is causing the problem, what happens if you
> remount read-only instead of unmounting before shutting down?
Yes, I'm happy to try these tests.
nb, the hibernate script is:
ethtool -s eth0 wol g
sync
echo platform > /sys/power/disk
echo disk > /sys/power/state

So there has always been a sync before any hibernate.


cu:~# mount -oremount,ro /huge
cu:~# mount
/dev/hda2 on / type xfs (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
usbfs on /proc/bus/usb type usbfs (rw)
tmpfs on /dev/shm type tmpfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
nfsd on /proc/fs/nfsd type nfsd (rw)
/dev/hda1 on /boot type ext3 (rw)
/dev/md0 on /huge type xfs (ro)
/dev/hdb2 on /scratch type xfs (rw)
tmpfs on /dev type tmpfs (rw,size=10M,mode=0755)
rpc_pipefs on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw)
cu:(pid2862,port1022) on /net type nfs 
(intr,rw,port=1022,toplvl,map=/usr/share/am-utils/amd.net,noac)
elm:/space on /amd/elm/root/space type nfs (rw,vers=3,proto=tcp)
elm:/space-backup on /amd/elm/root/space-backup type nfs (rw,vers=3,proto=tcp)
elm:/usr/src on /amd/elm/root/usr/src type nfs (rw,vers=3,proto=tcp)
cu:~# /usr/net/bin/hibernate
[this works and resumes]

cu:~# mount -oremount,rw /huge
cu:~# /usr/net/bin/hibernate
[this works and resumes too !]

cu:~# touch /huge/tst
cu:~# /usr/net/bin/hibernate
[but this doesn't even hibernate]




 > What about freezing the filesystem?
cu:~# xfs_freeze -f /huge
cu:~# /usr/net/bin/hibernate
[but this doesn't even hibernate - same as the 'touch']

Nb the screen looks like this:
http://www.dgreaves.com/pub/2.6.21-rc4-ptched-suspend-failure.jpg
whether it hangs on suspend or resume.

So I wouldn't say it *is* XFS at fault - but there certainly seems to be an 
interaction...
At least it's easily reproducible :) Shame about the sysrq

I can think of other permutations of freeze/ro/writing tests but I'm just 
thrashing really. Happy for you to tell me what to try next ...


David
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