Message-ID: <4FBF89C0.2030805@parallels.com>
Date:	Fri, 25 May 2012 17:31:44 +0400
From:	Stanislav Kinsbursky <skinsbursky@...allels.com>
To:	"Myklebust, Trond" <Trond.Myklebust@...app.com>
CC:	Dave Jones <davej@...hat.com>,
	"bfields@...ldses.org" <bfields@...ldses.org>,
	"linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: 3.4. sunrpc oops during shutdown

On 25.05.2012 17:07, Myklebust, Trond wrote:
> On Fri, 2012-05-25 at 12:12 +0400, Stanislav Kinsbursky wrote:
>> On 21.05.2012 22:03, Myklebust, Trond wrote:
>>> On Mon, 2012-05-21 at 13:14 -0400, Dave Jones wrote:
>>>> Tried to shutdown a machine, got this, and a bunch of hung processes.
>>>> There was one NFS mount mounted at the time.
>>>>
>>>> 	Dave
>>>>
>>>> BUG: unable to handle kernel NULL pointer dereference at 0000000000000028
>>>> IP: [<ffffffffa01191df>] svc_destroy+0x1f/0x140 [sunrpc]
>>>> PGD 1434c4067 PUD 144964067 PMD 0
>>>> Oops: 0000 [#1] PREEMPT SMP
>>>> CPU 4
>>>> Modules linked in: ip6table_filter(-) ip6_tables nfsd nfs fscache auth_rpcgss nfs_acl lockd ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6
>>>>
>>>> Pid: 6946, comm: ntpd Not tainted 3.4.0+ #13
>>>> RIP: 0010:[<ffffffffa01191df>]  [<ffffffffa01191df>] svc_destroy+0x1f/0x140 [sunrpc]
>>>> RSP: 0018:ffff880143c65c48  EFLAGS: 00010286
>>>> RAX: 0000000000000000 RBX: ffff880142cd41a0 RCX: 0000000000000006
>>>> RDX: 0000000000000040 RSI: ffff880143105028 RDI: ffff880142cd41a0
>>>> RBP: ffff880143c65c58 R08: 0000000000000000 R09: 0000000000000001
>>>> R10: 0000000000000000 R11: 0000000000000000 R12: ffff88013bc5a148
>>>> R13: ffff880140981658 R14: ffff880142cd41a0 R15: ffff880146c88000
>>>> FS:  00007fdc0382a740(0000) GS:ffff880149400000(0000) knlGS:0000000000000000
>>>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>> CR2: 0000000000000028 CR3: 0000000036cbb000 CR4: 00000000001407e0
>>>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>>> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
>>>> Process ntpd (pid: 6946, threadinfo ffff880143c64000, task ffff880143104940)
>>>> Stack:
>>>>    ffff880140981660 ffff88013bc5a148 ffff880143c65c88 ffffffffa01193a6
>>>>    0000000000000000 ffff88013e566020 ffff88013e565f28 ffff880146ee6ac0
>>>>    ffff880143c65ca8 ffffffffa024f403 ffff880143c65ca8 ffff880143d3a4f8
>>>> Call Trace:
>>>>    [<ffffffffa01193a6>] svc_exit_thread+0xa6/0xb0 [sunrpc]
>>>>    [<ffffffffa024f403>] nfs_callback_down+0x53/0x90 [nfs]
>>>>    [<ffffffffa021642e>] nfs_free_client+0xfe/0x120 [nfs]
>>>>    [<ffffffffa02185df>] nfs_put_client+0x29f/0x420 [nfs]
>>>>    [<ffffffffa02184e0>] ? nfs_put_client+0x1a0/0x420 [nfs]
>>>>    [<ffffffffa021962f>] nfs_free_server+0x16f/0x2e0 [nfs]
>>>>    [<ffffffffa02194e3>] ? nfs_free_server+0x23/0x2e0 [nfs]
>>>>    [<ffffffffa022363c>] nfs4_kill_super+0x3c/0x50 [nfs]
>>>>    [<ffffffff811ad67c>] deactivate_locked_super+0x3c/0xa0
>>>>    [<ffffffff811ae29e>] deactivate_super+0x4e/0x70
>>>>    [<ffffffff811ccba4>] mntput_no_expire+0xb4/0x100
>>>>    [<ffffffff811ccc16>] mntput+0x26/0x40
>>>>    [<ffffffff811cd597>] release_mounts+0x77/0x90
>>>>    [<ffffffff811cefc6>] put_mnt_ns+0x66/0x80
>>>>    [<ffffffff81078dff>] free_nsproxy+0x1f/0xb0
>>>>    [<ffffffff8107905e>] switch_task_namespaces+0x5e/0x70
>>>>    [<ffffffff81079080>] exit_task_namespaces+0x10/0x20
>>>>    [<ffffffff8104e90e>] do_exit+0x4ee/0xb80
>>>>    [<ffffffff81639c0a>] ? retint_swapgs+0xe/0x13
>>>>    [<ffffffff8104f2ef>] do_group_exit+0x4f/0xc0
>>>>    [<ffffffff8104f377>] sys_exit_group+0x17/0x20
>>>>    [<ffffffff81641352>] system_call_fastpath+0x16/0x1b
>>>> Code: 48 8b 5d f0 4c 8b 65 f8 c9 c3 66 90 55 48 89 e5 41 54 53 66 66 66 66 90 65 48 8b 04 25 80 ba 00 00 48 8b 80 50 05 00 00 48 89 fb<4c>   8b 60 28 8b 47 58 85 c0 0f 84 ec 00 00 00 83 e8 01 85 c0 89
>>>
>>> Aside from the fact that the current net_namespace is not guaranteed to
>>> exist when we are called from free_nsproxy, svc_destroy() looks
>>> seriously broken:
>>
>> Trond, looks like you are mistaken here.
>> Any process holds references to all namespaces it belong to (copy_net_ns()
>> increase usage counter). And network namespace is released after mount namespace
>> in free_nsproxy.
>
> That doesn't help you though. switch_task_namespaces will have already
> set current->nsproxy to NULL, which is why we Oops when we try to read
> current->nsproxy->net_ns in svc_exit_thread().
>
>>>
>>>         * On the one hand it is trying to free struct svc_serv (and
>>>           presumably all structures owned by struct svc_serv).
>>>         * On the other hand, it tries to pass a parameter to
>>>           svc_close_net() saying "please don't free structures on my
>>>           sv_tempsocks, or sv_permsocks list unless they match this net
>>>           namespace".
>>>
>>
>> I've sent patches, which moves svc_shutdown_net() from svc_destroy() ("SUNRPC:
>> separate per-net data creation from service").
>> with this patch set it's assumed, that per-net resources will be created or
>> released prior to service creation and destruction.
>
> Are those patches appropriate for inclusion in the stable kernel series
> so that we can fix 3.4?
>

Yes. But unfortunately, this won't be enough.
"NFS: callback threads containerization" patch set is required as well.

A a bugfix, I can suggest "SUNRPC: separate per-net data creation from service" 
patch set + pass hard-coded "init_net" for NFS callback shutdown routines 
(instead of current->nsproxy->net_ns). This should work.



-- 
Best regards,
Stanislav Kinsbursky
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