Thanks Bob,
We believe we have seen these issues from time to time in our automated testing
but I suspect that they're indicating a configuration problem with the backing
storage. For flexibility a proportion of our purely functional testing will use
storage provided by a VM running a software iSCSI target and these tests seem
to be somewhat susceptible to getting I/O errors, some of which will inevitably
end up being in the journal. If we start to see a lot we'll need to look at the
config of the VMs first I think.
Mark.
-----Original Message-----
From: Bob Peterson <rpete...@redhat.com>
Sent: 18 December 2018 15:52
To: Mark Syms <mark.s...@citrix.com>
Cc: cluster-devel@redhat.com
Subject: Re: [Cluster-devel] [GFS2 PATCH] gfs2: Panic when an io error occurs
writing
----- 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
