Re: [PATCH 12/13] loop: remove lo_refcount and avoid lo_mutex in ->open / ->release
- To: Jan Kara <jack@suse.cz>
- Cc: Christoph Hellwig <hch@lst.de>, Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>, Dave Chinner <david@fromorbit.com>, Jens Axboe <axboe@kernel.dk>, Josef Bacik <josef@toxicpanda.com>, Minchan Kim <minchan@kernel.org>, Nitin Gupta <ngupta@vflare.org>, "Darrick J . Wong" <djwong@kernel.org>, Ming Lei <ming.lei@redhat.com>, linux-block@vger.kernel.org, nbd@other.debian.org
- Subject: Re: [PATCH 12/13] loop: remove lo_refcount and avoid lo_mutex in ->open / ->release
- From: Christoph Hellwig <hch@lst.de>
- Date: Tue, 29 Mar 2022 15:14:27 +0200
- Message-id: <[🔎] 20220329131427.GA1848@lst.de>
- In-reply-to: <[🔎] 20220329094203.zkgkqtumix7nygs2@quack3.lan>
- References: <[🔎] 20220324075119.1556334-1-hch@lst.de> <[🔎] 20220324075119.1556334-13-hch@lst.de> <[🔎] 20220324141321.pqesnshaswwk3svk@quack3.lan> <[🔎] 96a4e2e7-e16e-7e89-255d-8aa29ffca68b@I-love.SAKURA.ne.jp> <[🔎] 20220324172335.GA28299@lst.de> <[🔎] 0b47dbee-ce17-7502-6bf3-fad939f89bb7@I-love.SAKURA.ne.jp> <[🔎] 20220325162331.GA16355@lst.de> <[🔎] 20220328083045.ryoh7rbhauxgezgn@quack3.lan> <[🔎] 20220329063921.GA19778@lst.de> <[🔎] 20220329094203.zkgkqtumix7nygs2@quack3.lan>
On Tue, Mar 29, 2022 at 11:42:03AM +0200, Jan Kara wrote:
> > entirely, as loop_clr_fd now is safe against concurrent users - it
> > has to anyway as there can be other users even without an open.
>
> Ah, OK, so you'd always set LO_AUTOCLEAR and leave cleanup to happen
> from lo_release()? That makes sense to me.
No, my idea was to never set LO_AUTOCLEAR. We have a frozen queue and
all protections in place to make clearing the file perfectly safe.
In fact the change_fd case also allows this.
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