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From: Christoph Hellwig <hch@lst.de>
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: 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>,
	Jan Kara <jack@suse.cz>, "Darrick J . Wong" <djwong@kernel.org>,
	Ming Lei <ming.lei@redhat.com>,
	Matteo Croce <mcroce@microsoft.com>,
	linux-block@vger.kernel.org, nbd@other.debian.org
Subject: Re: [PATCH 13/14] loop: remove lo_refcount and avoid lo_mutex in ->open / ->release
Date: Tue, 29 Mar 2022 15:25:02 +0200	[thread overview]
Message-ID: <20220329132502.GA2024@lst.de> (raw)
In-Reply-To: <20220329065234.GA20006@lst.de>

Thinking a bit more, I really don't think the existing any refcount
check protects us against a different tread modififying the backing
file.  When a process has a file descriptor to a loop device open
and is multithreaded (or forks) we can still have multiple threads
manipulating the loop state.

That being said I do not think we really need that refcount check
at all - once loop_clr_fd set lo->lo_state to Lo_rundown under the
global lock we know that loop_validate_file will error out on it
due to the lo_state != Lo_bound check.

  reply	other threads:[~2022-03-29 13:25 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-03-25  6:39 yet another approach to fix the loop lock order inversions v5 Christoph Hellwig
2022-03-25  6:39 ` [PATCH 01/14] nbd: use the correct block_device in nbd_bdev_reset Christoph Hellwig
2022-03-25  9:48   ` Jan Kara
2022-03-25  6:39 ` [PATCH 02/14] zram: cleanup reset_store Christoph Hellwig
2022-03-25  6:39 ` [PATCH 03/14] zram: cleanup zram_remove Christoph Hellwig
2022-03-25  6:39 ` [PATCH 04/14] block: add a disk_openers helper Christoph Hellwig
2022-03-25  6:39 ` [PATCH 05/14] block: turn bdev->bd_openers into an atomic_t Christoph Hellwig
2022-03-25  6:39 ` [PATCH 06/14] loop: de-duplicate the idle worker freeing code Christoph Hellwig
2022-03-25  6:39 ` [PATCH 07/14] loop: initialize the worker tracking fields once Christoph Hellwig
2022-03-25  6:39 ` [PATCH 08/14] loop: remove the racy bd_inode->i_mapping->nrpages asserts Christoph Hellwig
2022-03-25  6:39 ` [PATCH 09/14] loop: don't freeze the queue in lo_release Christoph Hellwig
2022-03-25  6:39 ` [PATCH 10/14] loop: only freeze the queue in __loop_clr_fd when needed Christoph Hellwig
2022-03-25  6:39 ` [PATCH 11/14] loop: implement ->free_disk Christoph Hellwig
2022-03-25 10:42   ` Tetsuo Handa
2022-03-25 15:10     ` Tetsuo Handa
2022-03-25  6:39 ` [PATCH 12/14] loop: suppress uevents while reconfiguring the device Christoph Hellwig
2022-03-25  9:49   ` Jan Kara
2022-03-25  6:39 ` [PATCH 13/14] loop: remove lo_refcount and avoid lo_mutex in ->open / ->release Christoph Hellwig
2022-03-26  2:52   ` Tetsuo Handa
2022-03-29  6:52     ` Christoph Hellwig
2022-03-29 13:25       ` Christoph Hellwig [this message]
2022-03-29 14:02         ` Tetsuo Handa
2022-03-29 14:49           ` Christoph Hellwig
2022-03-25  6:39 ` [PATCH 14/14] loop: don't destroy lo->workqueue in __loop_clr_fd Christoph Hellwig
2022-03-29 15:36 ` [PATCH 15/14] loop: avoid loop_validate_mutex/lo_mutex in ->release Tetsuo Handa
2022-03-30  8:14   ` Jan Kara

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