[Linux-cluster] self_fence for FS resource in RHEL 6.x operational?

[Robert Hayden]

On Tue, Jan 22, 2013 at 12:38 PM, Fabio M. Di Nitto <fdinitto at redhat.com> wrote:
>
> On 01/22/2013 06:22 PM, Robert Hayden wrote:
> > I am testing RHCS 6.3 and found that the self_fence option for a file
> > system resource will now longer function as expected.  Before I log an
> > SR with RH, I was wondering if the design changed between RHEL 5 and
> > RHEL 6.
> >
> > In RHEL 5, I see logic in /usr/share/cluster/fs.sh that will complete a
> > "reboot -fn" command on a self_fence logic.  In RHEL 6, there is little
> > to no logic around self_fence in the fs.sh file.
>
> The logic has just been moved to a common file shared by all *fs
> resources (fs-lib)
>
>
>
> >
> > Example of RHEL 5 logic in fs.sh that appears to be removed from RHEL 6:
> >         if [ -n "$umount_failed" ]; then
> >                 ocf_log err "'umount $mp' failed, error=$ret_val"
> >
> >                 if [ "$self_fence" ]; then
> >                         ocf_log alert "umount failed - REBOOTING"
> >                         sync
> >                         reboot -fn
> >                 fi
> >                 return $FAIL
> >         else
> >                 return $SUCCESS
> >         fi
>
> same code, just different file.
>
> >
> >
> >
> > To test in RHEL 6, I simply create a file system (e.g. /test/data)
> > resource with self_fence="1" or self_fence="on" (as added by Conga).
> > Then mount a small ISO image on top of the file system.  This mount will
> > cause the file system resource to be unable to unmount itself and should
> > trigger a self_fence scenario.
> >
> > Testing RHEL 6, I see the following in /var/log/messages:
> >
> > Jan 21 16:40:59 techval16 rgmanager[82637]: [fs] unmounting /test/data
> > Jan 21 16:40:59 techval16 rgmanager[82777]: [fs] Sending SIGTERM to
> > processes on /test/data
> > Jan 21 16:41:04 techval16 rgmanager[82859]: [fs] unmounting /test/data
> > Jan 21 16:41:05 techval16 rgmanager[82900]: [fs] Sending SIGKILL to
> > processes on /test/data
> > Jan 21 16:41:05 techval16 rgmanager[61929]: stop on fs "share16_data"
> > returned 1 (generic error)
>
> Looks like a bug in force_umount option.
>
> Please file a ticket with RH GSS.

I will log a ticket in a few days when I can build a simple test case
for support.

>
> As workaround try to disable force_umount.

The workaround of have force_umount=0 and self_fence=1 worked with the
ISO image mount test.


>
> As far as I can tell, but I haven't verify it:
> ocf_log warning "Sending SIGKILL to processes on $mp"
>                         fuser -kvm "$mp"
>
>                         case $? in
>                         0)
>                                 ;;
>                         1)
>                                 return $OCF_ERR_GENERIC
>                                 ;;
>                         2)
>                                 break
>                                 ;;
>                         esac
>
> the issue is the was fuser error is handled in force_umount path, that
> would match the log you are posting.
>

I have learned that "fuser" command will not find the sub-mounted iso
image that causes the umount to fail.  So, my test case using the iso
image to test self_fence may need to be updated.

[root at techval16]# df -k | grep data
/dev/mapper/share16vg-tv16_mq_data
                        806288     17200    748128   3% /test/data
                           352       352                 0 100% /test/data/mnt
[root at techval16]# fuser -kvm /test/data
[root at techval16]# echo $?
1
[root at techval16]# umount /test/data
umount: /test/data: device is busy.
        (In some cases useful info about processes that use
         the device is found by lsof(8) or fuser(1))
[root at techval16]#

Unsure if the logic in fs-lib needs to be updated to handle
sub-mounted file systems.  That is what the Support Ticket will
determine, I suppose.

> I think the correct way would be to check if self_fence is enabled or
> not and then return/reboot later on the script.
>
> Fabio
>
>
>
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