linux-kernel - Re: Issue with Race Condition on NFS4 with KRB

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Message-ID: <BANLkTin0HnH7rufrHJGgEuPc-ZPjkZe3iw@mail.gmail.com>
Date:	Wed, 22 Jun 2011 15:40:32 -0700
From:	Joshua Scoggins <theoretically.x64@...il.com>
To:	Trond Myklebust <Trond.Myklebust@...app.com>
Cc:	linux-kernel@...r.kernel.org, linux-nfs@...r.kernel.org
Subject: Re: Issue with Race Condition on NFS4 with KRB

The patch isn't applying to the 2.6.39 kernel sources.

-Josh

On Wed, Jun 22, 2011 at 2:51 PM, Trond Myklebust
<Trond.Myklebust@...app.com> wrote:
> On Wed, 2011-06-22 at 12:18 -0700, Joshua Scoggins wrote:
>> According to the it guys they are running solaris 10 as the server platform.
>
> Ok. That should not be subject to the race I was thinking of...
>
>> On Wed, Jun 22, 2011 at 11:57 AM, Trond Myklebust
>> <Trond.Myklebust@...app.com> wrote:
>> > On Wed, 2011-06-22 at 11:37 -0700, Joshua Scoggins wrote:
>> >> Here are our mount options from auto.master
>> >>
>> >> /user -fstype=nfs4,sec=krb5p,noresvport,noatime
>> >> /group -fstype=nfs4,sec=krb5p,noresvport,noatime
>> >>
>> >> As for the server, we don't control it. It's actually run by the
>> >> campus wide it department we are just lab support for CS. I can
>> >> potentially get the server information but I need to know what you want
>> >> specifically as they're pretty paranoid about giving out information about
>> >> their servers.
>> >
>> > I would just want to know _what_ server platform you are running
>> > against. I know of at least one server bug that might explain what you
>> > are seeing, and I'd like to eliminate that as a possibility.
>> >
>> > Trond
>> >
>> >> Joshua Scoggins
>> >>
>> >> On Wed, Jun 22, 2011 at 11:30 AM, Trond Myklebust
>> >> <Trond.Myklebust@...app.com> wrote:
>> >> > On Wed, 2011-06-22 at 11:21 -0700, Joshua Scoggins wrote:
>> >> >> Hello,
>> >> >>
>> >> >> We are trying to update our linux images in our CS lab and have it a
>> >> >> bit of an issue. We are
>> >> >> using nfs to load user home folder. While testing the new image we
>> >> >> found that the nfs4 module will
>> >> >>  crash when using firefox 3.6.17 for an extended period of time. Some
>> >> >> research via google yielded that
>> >> >> it's a potential race condition specific to nfs with krb auth with
>> >> >> newer kernels. Our old image doesn't have
>> >> >> this issue and it seems that its due to it running a far older kernel version.
>> >> >>
>> >> >> We have two images and both are having this problem. One is running
>> >> >> 2.6.39 and the other is 2.6.38.
>> >> >> Here is what dmesg spit out from the machine running 2.6.39 on one occasion:
>> >> >>
>> >> >> [  678.632061] ------------[ cut here ]------------
>> >> >> [  678.632068] WARNING: at net/sunrpc/clnt.c:1567 call_decode+0xb2/0x69c()
>> >> >> [  678.632070] Hardware name: OptiPlex 755
>> >> >> [  678.632072] Modules linked in: nvidia(P) scsi_wait_scan
>> >> >> [  678.632078] Pid: 3882, comm: kworker/0:2 Tainted: P
>> >> >> 2.6.39-gentoo-r1 #1
>> >> >> [  678.632080] Call Trace:
>> >> >> [  678.632086]  [<ffffffff81035b20>] warn_slowpath_common+0x80/0x98
>> >> >> [  678.632091]  [<ffffffff8117231e>] ? nfs4_xdr_dec_readdir+0xba/0xba
>> >> >> [  678.632094]  [<ffffffff81035b4d>] warn_slowpath_null+0x15/0x17
>> >> >> [  678.632097]  [<ffffffff81426f48>] call_decode+0xb2/0x69c
>> >> >> [  678.632101]  [<ffffffff8142d2b5>] __rpc_execute+0x78/0x24b
>> >> >> [  678.632104]  [<ffffffff8142d4c9>] ? rpc_execute+0x41/0x41
>> >> >> [  678.632107]  [<ffffffff8142d4d9>] rpc_async_schedule+0x10/0x12
>> >> >> [  678.632111]  [<ffffffff8104a49d>] process_one_work+0x1d9/0x2e7
>> >> >> [  678.632114]  [<ffffffff8104c402>] worker_thread+0x133/0x24f
>> >> >> [  678.632118]  [<ffffffff8104c2cf>] ? manage_workers+0x18d/0x18d
>> >> >> [  678.632121]  [<ffffffff8104f6a0>] kthread+0x7d/0x85
>> >> >> [  678.632125]  [<ffffffff8145e314>] kernel_thread_helper+0x4/0x10
>> >> >> [  678.632128]  [<ffffffff8104f623>] ? kthread_worker_fn+0x13a/0x13a
>> >> >> [  678.632131]  [<ffffffff8145e310>] ? gs_change+0xb/0xb
>> >> >> [  678.632133] ---[ end trace 6bfae002a63e020e ]---
>
> Looking at the code, there is only one way I can see for that warning to
> occur, and that is if we put the request back on the 'xprt->recv' list
> after it has already received a reply from the server.
>
> Can you reproduce the problem with the attached patch?
>
> Trond
>
> --
> Trond Myklebust
> Linux NFS client maintainer
>
> NetApp
> Trond.Myklebust@...app.com
> www.netapp.com
>
>
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