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From: Christoph Hellwig <hch@lst.de>
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Jan Kara <jack@suse.cz>, Christoph Hellwig <hch@lst.de>,
	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
Date: Thu, 24 Mar 2022 18:23:35 +0100	[thread overview]
Message-ID: <20220324172335.GA28299@lst.de> (raw)
In-Reply-To: <96a4e2e7-e16e-7e89-255d-8aa29ffca68b@I-love.SAKURA.ne.jp>

On Thu, Mar 24, 2022 at 11:24:43PM +0900, Tetsuo Handa wrote:
> On 2022/03/24 23:13, Jan Kara wrote:
> >> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> >> index b3170e8cdbe95..e1eb925d3f855 100644
> >> --- a/drivers/block/loop.c
> >> +++ b/drivers/block/loop.c
> >> @@ -1244,7 +1244,7 @@ static int loop_clr_fd(struct loop_device *lo)
> >>  	 * <dev>/do something like mkfs/losetup -d <dev> causing the losetup -d
> >>  	 * command to fail with EBUSY.
> >>  	 */
> >> -	if (atomic_read(&lo->lo_refcnt) > 1) {
> >> +	if (disk_openers(lo->lo_disk) > 1) {
> 
> This is sometimes "if (0) {" due to not holding disk->open_mutex.

Yes, as clearly documented in the commit log.  In fact turning it
into an explicit if 0 (that is removing this code) might be a not
bad idea either - the code was added to work around a

	if (lo->lo_refcnt > 1)  /* we needed one fd for the ioctl */
		return -EBUSY;

that already did not make much sense to start with (but goes
back to before git history).

But for now I'd really prefer to stop moving the goalpost further and
further.

  reply	other threads:[~2022-03-24 17:23 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-03-24  7:51 yet another approach to fix the loop lock order inversions v4 Christoph Hellwig
2022-03-24  7:51 ` [PATCH 01/13] nbd: use the correct block_device in nbd_ioctl Christoph Hellwig
2022-03-24 12:20   ` Jan Kara
2022-03-24 13:23     ` Jan Kara
2022-03-24 17:11       ` Christoph Hellwig
2022-03-25  9:39         ` Jan Kara
2022-03-24  7:51 ` [PATCH 02/13] zram: cleanup reset_store Christoph Hellwig
2022-03-24 12:21   ` Jan Kara
2022-03-24  7:51 ` [PATCH 03/13] zram: cleanup zram_remove Christoph Hellwig
2022-03-24 13:15   ` Jan Kara
2022-03-24  7:51 ` [PATCH 04/13] block: add a disk_openers helper Christoph Hellwig
2022-03-24 13:24   ` Jan Kara
2022-03-24  7:51 ` [PATCH 05/13] block: turn bdev->bd_openers into an atomic_t Christoph Hellwig
2022-03-24 13:31   ` Jan Kara
2022-03-24 17:12     ` Christoph Hellwig
2022-03-24  7:51 ` [PATCH 06/13] loop: de-duplicate the idle worker freeing code Christoph Hellwig
2022-03-24  7:51 ` [PATCH 07/13] loop: initialize the worker tracking fields once Christoph Hellwig
2022-03-24  7:51 ` [PATCH 08/13] loop: remove the racy bd_inode->i_mapping->nrpages asserts Christoph Hellwig
2022-03-24  7:51 ` [PATCH 09/13] loop: don't freeze the queue in lo_release Christoph Hellwig
2022-03-24  7:51 ` [PATCH 10/13] loop: only freeze the queue in __loop_clr_fd when needed Christoph Hellwig
2022-03-24  7:51 ` [PATCH 11/13] loop: implement ->free_disk Christoph Hellwig
2022-03-24  7:51 ` [PATCH 12/13] loop: remove lo_refcount and avoid lo_mutex in ->open / ->release Christoph Hellwig
2022-03-24 14:13   ` Jan Kara
2022-03-24 14:24     ` Tetsuo Handa
2022-03-24 17:23       ` Christoph Hellwig [this message]
2022-03-25 10:54         ` Tetsuo Handa
2022-03-25 16:23           ` Christoph Hellwig
2022-03-28  8:30             ` Jan Kara
2022-03-29  6:39               ` Christoph Hellwig
2022-03-29  9:42                 ` Jan Kara
2022-03-29  9:49                   ` Tetsuo Handa
2022-03-29 13:14                   ` Christoph Hellwig
2022-03-30  7:58                     ` Jan Kara
2022-03-24 17:15     ` Christoph Hellwig
2022-03-24 17:47       ` Christoph Hellwig
2022-03-25  9:34         ` Jan Kara
2022-03-24  7:51 ` [PATCH 13/13] loop: don't destroy lo->workqueue in __loop_clr_fd Christoph Hellwig
2022-03-24 14:14   ` Jan Kara

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