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Re: [libvirt] [PATCH] iscsi: do not fail to stop a stopped pool




On 04/29/2015 10:40 AM, Ján Tomko wrote:
> On Wed, Apr 29, 2015 at 10:10:11AM -0400, John Ferlan wrote:
>>
>>
>> On 04/29/2015 09:08 AM, Ján Tomko wrote:
>>> Just as we allow stopping filesystem pools when they were unmounted
>>> externally, do not fail to stop an iscsi pool when someone else
>>> closed the session externally.
>>>
>>> Resolves:
>>> https://bugzilla.redhat.com/show_bug.cgi?id=1171984
>>
>> For this I disagree - it doesn't resolve all the issues in 1171984.
> 
> I can remove the 'Resolves:' line.
> 

Fair enough

>> It
>> resolves a symptom of libvirt allowing more than one pool to use the
>> same session.
> 
> This resolves the error to stop a pool when there's no pool anymore,
> whether that's because someone called StopPool earlier on a pool that
> was duplicate but libvirt didn't catch it, or manually via messing with
> iscsiadm.
> 

I did some more testing of this and found one could start a domain using
the pool in the funky state which would cause the session to be logged
back in (I have authentication enabled too, so that could be a reason -
I didn't chase deeper)....

This patch only addresses failure to shutdown the second of the
duplicated pools, but trying to refresh the pool gets the same result -
that is an error since the session was logged out. However, if someone
calls refreshPool and there's a failure because of the logout, then the
pool gets marked as inactive.

The checkPool will be "tricked" into believing the pool isn't started
which shouldn't be a huge deal unless pool-autostart is set for the
pool. But I think someone would have expected (based on a recent series)
that if a pool was started, that it could survive a 'service libvirtd
restart'.

The findPoolSources, uploadVol, downloadVol, and wipeVol don't require
the session as they go direct to the block device

>>
>> While there is disagreement over the method I've taken :
>>
>> http://www.redhat.com/archives/libvir-list/2015-April/msg01197.html
>>
>> Simply "covering up" the original issue by just ignoring the error on
>> stop doesn't seem to be the best solution to me.
>>
> 
> The proposed series aims to detect duplicate pools on the same hosts.
> It does not deal with duplicate pools on different hosts.
> Even if we change the duplicate checks to only deal with the target,
> as I suggested here:
> https://www.redhat.com/archives/libvir-list/2015-April/msg00959.html
> (since libvirt's iscsi backend treats the same target on different hosts
> as a duplicate pool, but the check above does not), this patch also
> fixes stopping the pool after someone messes with iscsiadm manually,
> 
> 
As noted in my response, duplicated IQN's on truly different host names
(by name or address) is a different bug.  Not that it doesn't deserve to
be fixed, but let's take it one step at a time.

There's still another issue of how to resolve the "same host" when using
different IP address families...

John


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