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From:   Song Liu <song@kernel.org>
Date:   Fri, 7 Jul 2023 17:06:39 +0800
Message-ID: <CAPhsuW4XyaOG29Vg9OaYEhJxqxi+YbEY_16KDdvJ0p868UPxZQ@mail.gmail.com>
Subject: Re: [PATCH -next 1/2] md: don't quiesce in mddev_suspend()
To:     Yu Kuai <yukuai1@huaweicloud.com>
Cc:     xni@redhat.com, colyli@suse.de, linux-raid@vger.kernel.org,
        linux-kernel@vger.kernel.org, yi.zhang@huawei.com,
        yangerkun@huawei.com, "yukuai (C)" <yukuai3@huawei.com>
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On Wed, Jun 28, 2023 at 2:29=E2=80=AFPM Yu Kuai <yukuai1@huaweicloud.com> w=
rote:
>
> Hi,
>
> =E5=9C=A8 2023/06/28 9:29, Yu Kuai =E5=86=99=E9=81=93:
> > From: Yu Kuai <yukuai3@huawei.com>
> >
> > Some levels doesn't implement "pers->quiesce", for example
> > raid0_quiesce() is empty, and now that all levels will drop 'active_io'
> > until io is done, wait for 'active_io' to be 0 is enough to make sure a=
ll
> > normal io is done, and percpu_ref_kill() for 'active_io' will make sure
> > no new normal io can be dispatched. There is no need to call
> > "pers->quiesce" anymore from mddev_suspend().
>
> Just found that this patch actually prevent null_ptr_deref in some cases
> that "pers->quiesce" is NULl for some personalities, and caller of
> mddev_suspend() doesn't check this. For example, suspend_lo_store()
> checks "pers->quiesce" is not NULL before calling mddev_suspend(), while
> suspend_hi_store() doesn't.

Let's refactor the code so that suspend_lo_store() and suspend_hi_store()
share code for this logic.

Thanks,
Song