linux-kernel - Re: [PATCH] md: prevent incoreect update of resync/recovery offset

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Message-ID: <969460f8-9ed2-4535-8336-4a7c359f5708@yukuai.org.cn>
Date: Sat, 30 Aug 2025 19:04:16 +0800
From: Yu Kuai <hailan@...uai.org.cn>
To: Paul Menzel <pmenzel@...gen.mpg.de>, Li Nan <linan666@...weicloud.com>
Cc: song@...nel.org, yukuai3@...wei.com, linux-raid@...r.kernel.org,
 linux-kernel@...r.kernel.org, yangerkun@...wei.com, yi.zhang@...wei.com
Subject: Re: [PATCH] md: prevent incoreect update of resync/recovery offset

Hi,

在 2025/8/30 17:41, Paul Menzel 写道:
> Dear Nan,
>
>
> Thank you for your patch. I have some formal comments. In the 
> summary/title: incor*r*ect.
>
> Am 30.08.25 um 11:02 schrieb linan666@...weicloud.com:
>> From: Li Nan <linan122@...wei.com>
>>
>> In md_do_sync(), when md_sync_action returns ACTION_FROZEN, subsequent
>> call to md_sync_position() will return MaxSector. This causes
>> 'curr_resync' (and later 'recovery_offset') to be set to MaxSector too,
>> which incorrectly signals that recovery/resync has completed even though
>> disk data has not actually been updated.
>>
>> To fix this issue, skip updating any offset values when the sync acion
>
> ac*t*ion
>
>> is either FROZEN or IDLE.
>
> Maybe state that the same holds true for IDLE?
>
> Should these two cases be handled differently in `md_sync_position()`. 
> Does it semantically make sense, that the default of MaxSector is 
> returned?
>
Max sectors will return, however, following procedures will update
resync_offset to MaxSector, while recovery can be interuppted by the
concurrent frozen, can this will cause data lost.

>> Fixes: 7d9f107a4e94 ("md: use new helpers in md_do_sync()")
>> Signed-off-by: Li Nan <linan122@...wei.com>
>> ---
>>   drivers/md/md.c | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/md/md.c b/drivers/md/md.c
>> index e78f80d39271..6828a569e819 100644
>> --- a/drivers/md/md.c
>> +++ b/drivers/md/md.c
>> @@ -9397,6 +9397,9 @@ void md_do_sync(struct md_thread *thread)
>>       }
>>         action = md_sync_action(mddev);
>> +    if (action == ACTION_FROZEN || action == ACTION_IDLE)
>> +        goto skip;
>> +
>>       desc = md_sync_action_name(action);
>>       mddev->last_sync_action = action;
>
Please send a new verison with the typo fixed.

Thanks,
Kuai

>
> Kind regards,
>
> Paul
>