On Thu, Jun 07, 2007 at 02:59:58PM +0100, David Greaves wrote:

David Chinner wrote:

quoted

On Thu, Jun 07, 2007 at 11:30:05AM +0100, David Greaves wrote:

quoted

Tejun Heo wrote:

quoted

Hello,

David Greaves wrote:

quoted

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...

quoted

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 suspected as much :/

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.

sync just guarantees that metadata changes are logged and data is
on disk - it doesn't stop the filesystem from doing anything after
the sync...

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.

Ok, so it's not an obvious XFS problem...

quoted

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

.....

[this works and resumes]

Ok.

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

Interesting. That means something in the generic remount code
is affecting this.

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

Ok, so a clean inode is sufficient to prevent hibernate from working.

So, what's different between a sync and a remount?

do_remount_sb() does:

    599         shrink_dcache_sb(sb);
    600         fsync_super(sb);

of which a sync does neither. sync does what fsync_super() does in
different sort of way, but does not call sync_blockdev() on each
block device. It looks like that is the two main differences between
sync and remount - remount trims the dentry cache and syncs the blockdev,
sync doesn't.

quoted

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']

I suspect that the frozen filesystem might cause other problems
in the hibernate process. However, while a freeze calls sync_blockdev()
it does not trim the dentry cache.....

So, rather than a remount before hibernate, lets see if we can 
remove the dentries some other way to determine if removing excess
dentries/inodes from the caches makes a difference. Can you do:

# touch /huge/foo
# sync
# echo 1 > /proc/sys/vm/drop_caches
# hibernate

# touch /huge/bar
# sync
# echo 2 > /proc/sys/vm/drop_caches
# hibernate

# touch /huge/baz
# sync
# echo 3 > /proc/sys/vm/drop_caches
# hibernate

And see if any of those survive the suspend/resume?

Cheers,

Dave.
-- 
Dave Chinner
Principal Engineer
SGI Australian Software Group