linux-kernel - Re: [PATCH v5 01/14] md: don't ignore suspended array in md_check

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Date: Sun, 18 Feb 2024 10:34:08 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: Xiao Ni <xni@...hat.com>, Yu Kuai <yukuai1@...weicloud.com>
Cc: mpatocka@...hat.com, heinzm@...hat.com, blazej.kucman@...ux.intel.com,
 agk@...hat.com, snitzer@...nel.org, dm-devel@...ts.linux.dev,
 song@...nel.org, jbrassow@....redhat.com, neilb@...e.de, shli@...com,
 akpm@...l.org, linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org,
 yi.zhang@...wei.com, yangerkun@...wei.com, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH v5 01/14] md: don't ignore suspended array in
 md_check_recovery()

Hi,

在 2024/02/18 10:27, Xiao Ni 写道:
> On Sun, Feb 18, 2024 at 9:46 AM Yu Kuai <yukuai1@...weicloud.com> wrote:
>>
>> Hi,
>>
>> 在 2024/02/18 9:33, Xiao Ni 写道:
>>> The deadlock problem mentioned in this patch should not be right?
>>
>> No, I think it's right. Looks like you are expecting other problems,
>> like mentioned in patch 6, to be fixed by this patch.
> 
> Hi Kuai
> 
> Could you explain why step1 and step2 from this comment can happen
> simultaneously? From the log, the process should be
> The process is :
> dev_remove->dm_destroy->__dm_destroy->dm_table_postsuspend_targets(raid_postsuspend)
> -> dm_table_destroy(raid_dtr).
> After suspending the array, it calls raid_dtr. So these two functions
> can't happen simultaneously.

You're removing the target directly, however, dm can suspend the disk
directly, you can simplily:

1) dmsetup suspend xxx
2) dmsetup remove xxx

Please also take a look at other patches, why step 1) can't stop sync
thread.

Thanks,
Kuai

> 
> 
>>
>> Noted that this patch just fix one case that MD_RECOVERY_RUNNING can't
>> be cleared, I you are testing this patch alone, please make sure that
>> you still triggered the exactly same case:
>>
>> - MD_RCOVERY_RUNNING can't be cleared while array is suspended.
> 
> I'm not testing this patch. I want to understand the patch well. So I
> need to understand the issue first. I can't understand how this
> deadlock (step1,step2) happens.
> 
> Regards
> Xiao
>>
>> Thanks,
>> Kuai
>>
> 
> .
>