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SubjectRe: [PATCH -next 3/7] md: don't rely on 'mddev->pers' to be set in mddev_suspend()
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Hi,

在 2023/08/22 8:13, Song Liu 写道:
> On Thu, Aug 3, 2023 at 6:30 AM Yu Kuai <yukuai1@huaweicloud.com> wrote:
>>
>> From: Yu Kuai <yukuai3@huawei.com>
>>
>> Now that active io is initialized when mddev is allocated, it's safe to
>> call mddev_suspend() before 'mddev->pers' is set.
>>
>> This also prevent null-ptr-def in some cases that caller doesn't
>> guarantee 'mddev->pers' to be set.
>
> This description is a little confusing (to me at least). Please revise it.

Sorry about this, how about this:

'active_io' used to be initialized while the array is running, and
'mddev->pers' is set while the array is running as well. Hence caller
must hold 'reconfig_mutex' and guarantee 'mddev->pers' is set before
calling mddev_suspend().

Now that 'active_io' is initialized when mddev is allocated, such
restriction doesn't exist anymore. In the meantime, follow up patches
will refactor mddev_suspend(), hence add checking for 'mddev->pers' to
prevent null-ptr-deref.

Thanks,
Kuai

>
> Other than that, the set looks good to me.
>
> Thanks,
> Song
>
>>
>> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
>> ---
>> drivers/md/md.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/md/md.c b/drivers/md/md.c
>> index 897e94a9e47d..f14f2f0a9484 100644
>> --- a/drivers/md/md.c
>> +++ b/drivers/md/md.c
>> @@ -448,7 +448,7 @@ void mddev_suspend(struct mddev *mddev)
>> set_bit(MD_ALLOW_SB_UPDATE, &mddev->flags);
>> percpu_ref_kill(&mddev->active_io);
>>
>> - if (mddev->pers->prepare_suspend)
>> + if (mddev->pers && mddev->pers->prepare_suspend)
>> mddev->pers->prepare_suspend(mddev);
>>
>> wait_event(mddev->sb_wait, percpu_ref_is_zero(&mddev->active_io));
>> --
>> 2.39.2
>>
> .
>

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