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Date:   Tue, 19 Jul 2022 07:06:55 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Song Liu <song@kernel.org>
Cc:     Hannes Reinecke <hare@suse.de>, Christoph Hellwig <hch@lst.de>,
        Logan Gunthorpe <logang@deltatee.com>,
        linux-raid <linux-raid@vger.kernel.org>,
        linux-block@vger.kernel.org
Subject: Re: [PATCH 09/10] md: only delete entries from all_mddevs when the
 disk is freed
Message-ID: <20220719050655.GA26785@lst.de>
References: <20220718063410.338626-1-hch@lst.de> <20220718063410.338626-10-hch@lst.de> <b8521a53-fb41-279c-dc43-580e8d0de045@suse.de> <CAPhsuW6VYLt0hPsa667mr5+Zn1pxjY_670NaD8+No=2ZjoOzYg@mail.gmail.com>
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On Mon, Jul 18, 2022 at 11:20:39AM -0700, Song Liu wrote:
> > >   static inline struct mddev *mddev_get(struct mddev *mddev)
> > >   {
> > > +     lockdep_assert_held(&all_mddevs_lock);
> > > +
> > > +     if (mddev->deleted)
> > > +             return NULL;
> > >       atomic_inc(&mddev->active);
> > >       return mddev;
> > >   }
> >
> > Why can't we use 'atomic_inc_unless_zero' here and do away with the
> > additional 'deleted' flag?

> I think atomic_inc_unless_zero() should work here. Alternatively, we can
> also grab a big from mddev->flags as MD_DELETED.

s/big/bit/ ?

Yes, this could use mddev->flags.  I don't think atomic_inc_unless_zero
would work, as an array can have a refcount of 0 but we still allow
to take new references to it, the deletion only happens if the other
conditions in mddev_put are met.

Do you want me to repin the series using a flag?