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Date:   Thu, 22 Oct 2020 09:24:46 +0900
From:   "Dae R. Jeong" <dae.r.jeong@kaist.ac.kr>
To:     Song Liu <song@kernel.org>
Cc:     yjkwon@kaist.ac.kr, linux-raid <linux-raid@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>
Subject: Re: WARNING in md_ioctl
Message-ID: <20201022002446.GB1811280@dragonet>
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> > > diff --git i/drivers/md/md.c w/drivers/md/md.c
> > > index 6072782070230..49442a3f4605b 100644
> > > --- i/drivers/md/md.c
> > > +++ w/drivers/md/md.c
> > > @@ -7591,8 +7591,10 @@ static int md_ioctl(struct block_device *bdev,
> > > fmode_t mode,
> > >                         err = -EBUSY;
> > >                         goto out;
> > >                 }
> > > -               WARN_ON_ONCE(test_bit(MD_CLOSING, &mddev->flags));
> > > -               set_bit(MD_CLOSING, &mddev->flags);
> > > +               if (test_and_set_bit(MD_CLOSING, &mddev->flags)) {
> > > +                       err = -EBUSY;
> > > +                       goto out;
> > > +               }
> > >                 did_set_md_closing = true;
> > >                 mutex_unlock(&mddev->open_mutex);
> > >                 sync_blockdev(bdev);
> > >
> 
> Good catch! The fix looks good. Would you like to submit a patch for it?

Sure. I will send a patch soon.

Best regards,
Dae R. Jeong.