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

[yu kuai]

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.

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

-- 
Thanks,
Kuai