[Cluster-devel] [GFS2 PATCH] gfs2: Panic when an io error occurs writing

[Bob Peterson <rpeterso@redhat.com>]

----- Original Message -----
> Hi Bob,
> 
> I agree, it's a hard problem. I'm just trying to understand that we've done
> the absolute best we can and that if this condition is hit then the best
> solution really is to just kill the node. I guess it's also a question of
> how common this actually ends up being. We have now got customers starting
> to use GFS2 for VM storage on XenServer so I guess we'll just have to see
> how many support calls we get in on it.
> 
> Thanks,
> 
> Mark.

Hi Mark,

I don't expect the problem to be very common in the real world. 
The user has to get IO errors while writing to the GFS2 journal, which is
not very common. The patch is basically reacting to a phenomenon we
recently started noticing in which the HBA (qla2xxx) driver shuts down
and stops accepting requests when you do abnormal reboots (which we sometimes
do to test node recovery). In these cases, the node doesn't go down right away.
It stays up just long enough to cause IO errors with subsequent withdraws,
which, we discovered, results in file system corruption.
Normal reboots, "/sbin/reboot -fin", and "echo b > /proc/sysrq-trigger" should
not have this problem, nor should node fencing, etc.

And like I said, I'm open to suggestions on how to fix it. I wish there was a
better solution.

As it is, I'd kind of like to get something into this merge window for the
upstream kernel, but I'll need to submit the pull request for that probably
tomorrow or Thursday. If we find a better solution, we can always revert these
changes and implement a new one.

Regards,

Bob Peterson