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Message-ID: <5dc1b00f-0451-bb0d-56e4-6c178d3c2ce7@garloff.de>
Date:   Tue, 27 Sep 2022 20:59:31 +0200
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To:     Thorsten Leemhuis <regressions@leemhuis.info>,
        Greg KH <gregkh@linuxfoundation.org>,
        Sasha Levin <sashal@kernel.org>
Cc:     "anna@kernel.org" <anna@kernel.org>,
        "linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>,
        "it+linux-nfs@molgen.mpg.de" <it+linux-nfs@molgen.mpg.de>,
        "pmenzel@molgen.mpg.de" <pmenzel@molgen.mpg.de>,
        Trond Myklebust <trondmy@hammerspace.com>
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From:   Kurt Garloff <kurt@garloff.de>
Subject: Re: nfs_scan_commit: BUG: unable to handle page fault for address:
 000000001d473c07
In-Reply-To: <0e1263a1-9d3d-a6cf-deb7-197ab1eed437@leemhuis.info>
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Hi Thorsten,

thanks for collecting this issue and providing relevant context!

On 26/09/2022 08:00, Thorsten Leemhuis wrote:

> [adding Greg and Sasha to the recipients, to ensure they see this; CCing
> Kurt as well, to keep him in the loop]
>
> On 22.09.22 15:44, Trond Myklebust wrote:
>> On Thu, 2022-09-22 at 13:42 +0200, Paul Menzel wrote:
>>> Am 21.09.22 um 14:44 schrieb Trond Myklebust:
>>>> On Wed, 2022-09-21 at 13:42 +0200, Paul Menzel wrote:
>>>>> Moving from Linux 5.10.113 to 5.15.69, starting Mozilla
>>>>> Thunderbird or
>>>>> Mozilla Firefox with the home on NFS, both programs get killed,
>>>>> and
>>>>> Linux 5.15.69 logs:
>>>>>
>>>>> ```
>>>>> [ 3827.604396] BUG: unable to handle page fault for address:
>>>>> 000000001d473c07
>>>>> [ 3827.611297] #PF: supervisor read access in kernel mode
>>>>> [ 3827.616452] #PF: error_code(0x0000) - not-present page
>>>>> [ 3827.621604] PGD 0 P4D 0
>>>>> [ 3827.624152] Oops: 0000 [#1] SMP PTI
>>>>> [ 3827.627657] CPU: 0 PID: 2378 Comm: firefox Not tainted
>>>>> 5.15.69.mx64.435 #1
>>>>> [ 3827.634551] Hardware name: Dell Inc. Precision Tower
>>>>> 3620/0MWYPT, BIOS 2.20.0 12/09/2021
>>> […]
>>>
>>>>> [ 3827.743328] Call Trace:
>>>>> [ 3827.745779]  <TASK>
>>>>> [ 3827.747883]  nfs_scan_commit+0x76/0xb0 [nfs]
>>>>> [ 3827.752167]  __nfs_commit_inode+0x108/0x180 [nfs]
>>>>> [ 3827.756886]  nfs_wb_all+0x59/0x110 [nfs]
>>>>> [ 3827.760822]  nfs4_inode_return_delegation+0x58/0x90 [nfsv4]
>>>>> [ 3827.766413]  nfs4_proc_remove+0x101/0x110 [nfsv4]
>>>>> [ 3827.771130]  nfs_unlink+0xf5/0x2d0 [nfs]
>>>>> [ 3827.775065]  vfs_unlink+0x10b/0x280
>>>>> [ 3827.778563]  do_unlinkat+0x19e/0x2c0
>>>>> [ 3827.782158]  __x64_sys_unlink+0x3e/0x60
>>>>> [ 3827.786002]  ? __x64_sys_readlink+0x1b/0x30
>>>>> [ 3827.790192]  do_syscall_64+0x40/0x90
>>>>> [ 3827.793779]  entry_SYSCALL_64_after_hwframe+0x61/0xcb
>>> […]
>>>
>>>>> ```
>>>>>
>>>> Does cherry-picking commit 6e176d47160c ("NFSv4: Fixes for
>>>> nfs4_inode_return_delegation()") into 5.15.69 from the upstream
>>>> kernel
>>>> tree fix the problem?
>>>>
>>>> 8<---------------------------------------------------
>>>>  From 6e176d47160cec8bcaa28d9aa06926d72d54237c Mon Sep 17 00:00:00
>>>> 2001
>>>> From: Trond Myklebust <trond.myklebust@hammerspace.com>
>>>> Date: Sun, 10 Oct 2021 10:58:12 +0200
>>>> Subject: [PATCH] NFSv4: Fixes for nfs4_inode_return_delegation()
>>> […]
>>>
>>> Indeed with that commit, present since v5.16-rc1, we are unable to
>>> reproduce the issue, so it seems to be the fix. It looks like there
>>> are
>>> not a lot of 5.15 NFS users out there. ;-)
>>>
>> I believe this is a dependency that was introduced by the back port of
>> commit e591b298d7ec ("NFS: Save some space in the inode") into 5.15.68.
>> So the reason it wasn't seen is because the change is very recent.
> Side note: I wonder if that is causing this problem from Kurt as well:
> https://lore.kernel.org/all/f6755107-b62c-a388-0ab5-0a6633bf9082@garloff.de/

Looks like it:
After confirming that the 5.15.69 kernel worked again fine backing out
those last three NFS commits, I reapplied them and cherry-picked commit
6e176d47160c as suggested. The kernel worked flawlessly thus far, so this
seems to indeed be a requirement for e591b298d7ec not to cause harm.

>> FYI Greg and Sasha: please also consider pulling 6e176d47160c ("NFSv4:
>> Fixes for nfs4_inode_return_delegation()") into that stable series.
> Greg, I noticed you in the past few days added quite a few patches into
> the queue for the next 5.15.y release, but this one was not among them
> afaics. So just to be sure: is that still on your todo list or is more
> needed to get 6e176d47160c added in time for the next stable -rc?

So by all means, Greg, please put this in the stable queue unless the
NFS wizards out there consider it safer to revert e591b298d7ec instead.

Thanks,

-- 
Kurt Garloff <kurt@garloff.de>
Cologne, Germany