From: Guoqing Jiang <guoqing.jiang@linux.dev>
To: Yu Kuai <yukuai3@huawei.com>, Marc Smith <msmith626@gmail.com>
Cc: Donald Buczek <buczek@molgen.mpg.de>, Song Liu <song@kernel.org>,
linux-raid@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
it+raid@molgen.mpg.de
Subject: Re: md_raid: mdX_raid6 looping after sync_action "check" to "idle" transition
Date: Wed, 15 Mar 2023 17:30:21 +0800 [thread overview]
Message-ID: <9dc19483-de0f-e8c6-bf18-10c33d0a35fd@linux.dev> (raw)
In-Reply-To: <60829bc7-2eb9-f4ca-1a36-d2dbda5b0f3e@huawei.com>
On 3/15/23 11:02, Yu Kuai wrote:
>
>
> 在 2023/03/14 21:55, Guoqing Jiang 写道:
>>
>>
>> On 3/14/23 21:25, Marc Smith wrote:
>>> On Mon, Feb 8, 2021 at 7:49 PM Guoqing Jiang
>>> <guoqing.jiang@cloud.ionos.com> wrote:
>>>> Hi Donald,
>>>>
>>>> On 2/8/21 19:41, Donald Buczek wrote:
>>>>> Dear Guoqing,
>>>>>
>>>>> On 08.02.21 15:53, Guoqing Jiang wrote:
>>>>>>
>>>>>> On 2/8/21 12:38, Donald Buczek wrote:
>>>>>>>> 5. maybe don't hold reconfig_mutex when try to unregister
>>>>>>>> sync_thread, like this.
>>>>>>>>
>>>>>>>> /* resync has finished, collect result */
>>>>>>>> mddev_unlock(mddev);
>>>>>>>> md_unregister_thread(&mddev->sync_thread);
>>>>>>>> mddev_lock(mddev);
>>>>>>> As above: While we wait for the sync thread to terminate,
>>>>>>> wouldn't it
>>>>>>> be a problem, if another user space operation takes the mutex?
>>>>>> I don't think other places can be blocked while hold mutex,
>>>>>> otherwise
>>>>>> these places can cause potential deadlock. Please try above two
>>>>>> lines
>>>>>> change. And perhaps others have better idea.
>>>>> Yes, this works. No deadlock after >11000 seconds,
>>>>>
>>>>> (Time till deadlock from previous runs/seconds: 1723, 37, 434, 1265,
>>>>> 3500, 1136, 109, 1892, 1060, 664, 84, 315, 12, 820 )
>>>> Great. I will send a formal patch with your reported-by and tested-by.
>>>>
>>>> Thanks,
>>>> Guoqing
>>> I'm still hitting this issue with Linux 5.4.229 -- it looks like 1/2
>>> of the patches that supposedly resolve this were applied to the stable
>>> kernels, however, one was omitted due to a regression:
>>> md: don't unregister sync_thread with reconfig_mutex held (upstream
>>> commit 8b48ec23cc51a4e7c8dbaef5f34ebe67e1a80934)
> Hi, Guoqing,
>
> Just borrow this thread to discuss, I think this commit might have
> problem in some corner cases:
>
> t1: t2:
> action_store
> mddev_lock
> if (mddev->sync_thread)
> mddev_unlock
> md_unregister_thread
> md_check_recovery
> set_bit(MD_RECOVERY_RUNNING, &mddev->recovery)
> queue_work(md_misc_wq, &mddev->del_work)
> mddev_lock_nointr
> md_reap_sync_thread
> // clear running
> mddev_lock
>
> t3:
> md_start_sync
> // running is not set
What does 'running' mean? MD_RECOVERY_RUNNING?
> Our test report a problem that can be cause by this in theory, by we
> can't be sure for now...
I guess you tried to describe racy between
action_store -> md_register_thread
and
md_start_sync -> md_register_thread
Didn't you already fix them in the series?
[PATCH -next 0/5] md: fix uaf for sync_thread
Sorry, I didn't follow the problem and also your series, I might try your
test with latest mainline kernel if the test is available somewhere.
> We thought about how to fix this, instead of calling
> md_register_thread() here to wait for sync_thread to be done
> synchronisely,
IMO, md_register_thread just create and wake a thread, not sure why it
waits for sync_thread.
> we do this asynchronously like what md_set_readonly() and
> do_md_stop() does.
Still, I don't have clear picture about the problem, so I can't judge it.
Thanks,
Guoqing
next prev parent reply other threads:[~2023-03-15 9:30 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-28 12:25 md_raid: mdX_raid6 looping after sync_action "check" to "idle" transition Donald Buczek
2020-11-30 2:06 ` Guoqing Jiang
2020-12-01 9:29 ` Donald Buczek
2020-12-02 17:28 ` Donald Buczek
2020-12-03 1:55 ` Guoqing Jiang
2020-12-03 11:42 ` Donald Buczek
2020-12-21 12:33 ` Donald Buczek
2021-01-19 11:30 ` Donald Buczek
2021-01-20 16:33 ` Guoqing Jiang
2021-01-23 13:04 ` Donald Buczek
2021-01-25 8:54 ` Donald Buczek
2021-01-25 21:32 ` Donald Buczek
2021-01-26 0:44 ` Guoqing Jiang
2021-01-26 9:50 ` Donald Buczek
2021-01-26 11:14 ` Guoqing Jiang
2021-01-26 12:58 ` Donald Buczek
2021-01-26 14:06 ` Guoqing Jiang
2021-01-26 16:05 ` Donald Buczek
2021-02-02 15:42 ` Guoqing Jiang
2021-02-08 11:38 ` Donald Buczek
2021-02-08 14:53 ` Guoqing Jiang
2021-02-08 18:41 ` Donald Buczek
2021-02-09 0:46 ` Guoqing Jiang
2021-02-09 9:24 ` Donald Buczek
2023-03-14 13:25 ` Marc Smith
2023-03-14 13:55 ` Guoqing Jiang
2023-03-14 14:45 ` Marc Smith
2023-03-16 15:25 ` Marc Smith
2023-03-29 0:01 ` Song Liu
2023-08-22 21:16 ` Dragan Stancevic
2023-08-23 1:22 ` Yu Kuai
2023-08-23 15:33 ` Dragan Stancevic
2023-08-24 1:18 ` Yu Kuai
2023-08-28 20:32 ` Dragan Stancevic
2023-08-30 1:36 ` Yu Kuai
2023-09-05 3:50 ` Yu Kuai
2023-09-05 13:54 ` Dragan Stancevic
2023-09-13 9:08 ` Donald Buczek
2023-09-13 14:16 ` Dragan Stancevic
2023-09-14 6:03 ` Donald Buczek
2023-09-17 8:55 ` Donald Buczek
2023-09-24 14:35 ` Donald Buczek
2023-09-25 1:11 ` Yu Kuai
2023-09-25 9:11 ` Donald Buczek
2023-09-25 9:32 ` Yu Kuai
2023-03-15 3:02 ` Yu Kuai
2023-03-15 9:30 ` Guoqing Jiang [this message]
2023-03-15 9:53 ` Yu Kuai
2023-03-15 7:52 ` Donald Buczek
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