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SubjectRe: [PATCH] md: Don't clear MD_CLOSING when the raid is about to stop
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Hi,

在 2023/12/11 17:56, Mariusz Tkaczyk 写道:
> On Mon, 11 Dec 2023 16:17:14 +0800
> linan666@huaweicloud.com wrote:
>
>> From: Li Nan <linan122@huawei.com>
>>
>> The raid should not be opened anymore when it is about to be stopped.
>> However, other processes can open it again if the flag MD_CLOSING is
>> cleared before exiting. From now on, this flag will not be cleared when
>> the raid will be stopped.
>>
>> Fixes: 065e519e71b2 ("md: MD_CLOSING needs to be cleared after called
>> md_set_readonly or do_md_stop") Signed-off-by: Li Nan <linan122@huawei.com>
>
> Hello Li Nan,
> I was there when I needed to fix this:
> https://git.kernel.org/pub/scm/linux/kernel/git/song/md.git/commit/?h=md-next&id=c8870379a21fbd9ad14ca36204ccfbe9d25def43
>
> For sure, you have to consider applying same solution for array_store "clear".
> Minor nit below.
>
> Thanks,
> Mariusz
>
>> ---
>> drivers/md/md.c | 8 +++-----
>> 1 file changed, 3 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/md/md.c b/drivers/md/md.c
>> index 4e9fe5cbeedc..ebdfc9068a60 100644
>> --- a/drivers/md/md.c
>> +++ b/drivers/md/md.c
>> @@ -6238,7 +6238,6 @@ static void md_clean(struct mddev *mddev)
>> mddev->persistent = 0;
>> mddev->level = LEVEL_NONE;
>> mddev->clevel[0] = 0;
>> - mddev->flags = 0;
>
> I recommend (safety recommendation):
> mddev->flags = MD_CLOSING;

Taking a look I think both MD_CLOSING and MD_DELETED should not be
cleared, however, there is no guarantee that MD_CLOSING will be set
before md_clean, because mdadm can be removed without running. Hence I
think just set MD_CLOSING is werid.

I think the proper way is to keep MD_CLOSING and MD_DELETED if they are
set. However, there is no such api to clear other bits at once. Since
we're not expecting anyone else to write flags, following maybe
acceptable:

mddev->flags &= BIT_ULL_MASK(MD_CLOSING) | BIT_ULL_MASK(MD_DELETED);

Or after making sure other flags cannot race, this patch is ok.

Thanks,
Kuai

>
> Unless you can prove that other flags cannot race.
>
>> mddev->sb_flags = 0;
>> mddev->ro = MD_RDWR;
>> mddev->metadata_type[0] = 0;
>
> .
>

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