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From:   Anna Schumaker <anna.schumaker@netapp.com>
Date:   Tue, 22 Sep 2020 12:11:46 -0400
Message-ID: <CAFX2JfmPNMbM3FShzP-WbVf+=8iTNs__wRGk-M5waLoQpP1WUQ@mail.gmail.com>
Subject: Re: [PATCH 1/3] NFSv4: Fix a livelock when CLOSE pre-emptively bumps
 state sequence
To:     Benjamin Coddington <bcodding@redhat.com>
Cc:     Trond Myklebust <trond.myklebust@hammerspace.com>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>
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On Tue, Sep 22, 2020 at 11:53 AM Anna Schumaker
<anna.schumaker@netapp.com> wrote:
>
> On Tue, Sep 22, 2020 at 11:49 AM Benjamin Coddington
> <bcodding@redhat.com> wrote:
> >
> > On 22 Sep 2020, at 10:43, Anna Schumaker wrote:
> >
> > > On Tue, Sep 22, 2020 at 10:31 AM Anna Schumaker
> > > <anna.schumaker@netapp.com> wrote:
> > >>
> > >> On Tue, Sep 22, 2020 at 10:22 AM Benjamin Coddington
> > >> <bcodding@redhat.com> wrote:
> > >>>
> > >>> On 22 Sep 2020, at 10:03, Anna Schumaker wrote:
> > >>>> Hi Ben,
> > >>>>
> > >>>> Once I apply this patch I have trouble with generic/478 doing lock
> > >>>> reclaim:
> > >>>>
> > >>>> [  937.460505] run fstests generic/478 at 2020-09-22 09:59:14
> > >>>> [  937.607990] NFS: __nfs4_reclaim_open_state: Lock reclaim failed!
> > >>>>
> > >>>> And the test just hangs until I kill it.
> > >>>>
> > >>>> Just thought you should know!
> > >>>
> > >>> Yes, thanks!  I'm not seeing that..  I've tested these based on
> > >>> v5.8.4, I'll
> > >>> rebase and check again.  I see a wirecap of generic/478 is only 515K
> > >>> on my
> > >>> system, would you be willing to share a capture of your test
> > >>> failing?
> > >>
> > >> I have it based on v5.9-rc6 (plus the patches I have queued up for
> > >> v5.10), so there definitely could be a difference there! I'm using a
> > >> stock kernel on my server, though :)
> > >>
> > >> I can definitely get you a packet trace once I re-apply the patch and
> > >> rerun the test.
> > >
> > > Here's the packet trace, I reran the test with just this patch applied
> > > on top of v5.9-rc6 so it's not interacting with something else in my
> > > tree. Looks like it's ending up in an NFS4ERR_OLD_STATEID loop.
> >
> > Thanks very much!
> >
> > Did you see this failure with all three patches applied, or just with
> > the
> > first patch?
>
> I saw it with the first patch applied, and with the first and third
> applied. I initially hit it as I was wrapping up for the day
> yesterday, but I left out #2 since I saw your retraction

I reran with all three patches applied, and didn't have the issue. So
something in the refactor patch fixes it.

Anna

>
> >
> > I see the client get two OPEN responses, but then is sending
> > TEST_STATEID
> > with the first seqid.  Seems like seqid 2 is getting lost.  I wonder if
> > we're making a bad assumption that NFS_OPEN_STATE can only be toggled
> > under
> > the so_lock.
> >
> > Ben
> >