Re: [PATCH] md: avoid modifying spares while the array is not suspended

[Abd-Alrhman Masalkhi]

Hi Kuai,

On Wed, Jul 08, 2026 at 16:32 +0800, yu kuai wrote:
> Hi,
>
> 在 2026/7/7 18:35, Abd-Alrhman Masalkhi 写道:
>> Hi Kuai,
>>
>> On Tue, Jul 07, 2026 at 09:12 +0800, yu kuai wrote:
>>> Hi,
>>>
>>> 在 2026/7/6 3:58, Abd-Alrhman Masalkhi 写道:
>>>>> The problem looks real, however, I think this will cause a change that user will be awared,
>>>>> if there are really spares that can be removed from conf, but array is not suspended here,
>>>>> user will still expect rdev will be removed from conf automatically.
>>>>>
>>>>> In md_start_sync, if suspend is false, can we check again after mddev_lock? If suspend is
>>>>> supposed to be true, we can release the lock and retry with suspend = true.
>>>>>
>>>> Yes, I see, and your approach is much better. But what do you think
>>>> about taking the lock first and then checking only once?
>>> I don't get what you mean. If we take the lock and then check that array should
>>> suspend, we still have to release the lock before we suspend the array.
>>>
>> Sorry, I was not clear. I meant, do we need to check twice, once before
>> taking the lock and once after? It seems that the check before taking the
>> lock is redundant. since the result would need to be checked again after
>> taking the lock anyway.
>>
>> Could we drop the check before taking the lock and only check whether
>> suspension is needed once while holding it? If suspension is needed, we
>> would release the lock, suspend the array, and then reacquire the lock.
>
> Thanks for the explanation, I understand now. Howerver, I still prefer to check
> first before holding the lock. Because the checking is much lower overhead than
> acquire reconfig_mutex, and the race window that rdev become spare is small, so
> it's unlikely we'll acquire reconfig_mtuex twice.
>

I see, thanks for the explanation. I'll send a v2 shortly.

>>
>>> -- 
>>> Thanks,
>>> Kuai
>
> -- 
> Thanks,
> Kuai

-- 
Best Regards,
Abd-Alrhman