From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Jan Kara <jack@suse.cz>, Kai-Heng Feng <kaihengfeng@me.com>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org,
John Lenton <john.lenton@canonical.com>,
jean-baptiste.lallement@canonical.com
Subject: Re: [PATCH] loop: Don't change loop device under exclusive opener
Date: Tue, 30 Jul 2019 19:16:19 +0900 [thread overview]
Message-ID: <f7e6717f-be46-1dfe-80ed-f85a18065c85@i-love.sakura.ne.jp> (raw)
In-Reply-To: <20190730092939.GB28829@quack2.suse.cz>
On 2019/07/30 18:29, Jan Kara wrote:
>> This patch introduced a regression [1].
>> A reproducer can be found at [2].
>>
>> [1] https://bugs.launchpad.net/bugs/1836914
>> [2] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1836914/comments/4
>
> Thanks for the notice and the references. What's your version of
> util-linux? What your test script does is indeed racy. You have there:
>
> echo Running:
> for i in {a..z}{a..z}; do
> mount $i.squash /mnt/$i &
> done
>
> So all mount(8) commands will run in parallel and race to setup loop
> devices with LOOP_SET_FD and mount them. However util-linux (at least in
> the current version) seems to handle EBUSY from LOOP_SET_FD just fine and
> retries with the new loop device. So at this point I don't see why the patch
> makes difference... I guess I'll need to reproduce and see what's going on
> in detail.
Firstly, why not to check the return value of blkdev_get() ?
EBUSY is not the only error code blkdev_get() might return.
/*
* If we don't hold exclusive handle for the device, upgrade to it
* here to avoid changing device under exclusive owner.
*/
if (!(mode & FMODE_EXCL)) {
bdgrab(bdev);
error = blkdev_get(bdev, mode | FMODE_EXCL, loop_set_fd);
- if (error)
+ if (error) {
+ printk("loop_set_fd: %d\n", error);
goto out_putf;
+ }
}
And try finding which line is returning an error
(like https://marc.info/?l=linux-xfs&m=156437221703110 does).
prev parent reply other threads:[~2019-07-30 10:16 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-16 14:01 [PATCH] loop: Don't change loop device under exclusive opener Jan Kara
2019-05-16 20:44 ` Jens Axboe
2019-05-27 12:29 ` Jan Kara
2019-05-27 13:34 ` Jens Axboe
2019-07-18 8:15 ` Kai-Heng Feng
2019-07-30 9:29 ` Jan Kara
2019-07-30 9:36 ` John Lenton
2019-07-30 10:16 ` Jan Kara
2019-07-30 13:36 ` Jan Kara
2019-07-30 17:59 ` Kai-Heng Feng
2019-07-30 19:17 ` Jens Axboe
2019-07-30 21:11 ` John Lenton
2019-07-31 8:56 ` Jan Kara
2019-08-05 16:41 ` Bart Van Assche
2019-08-05 21:01 ` Tetsuo Handa
2019-08-07 9:45 ` Jan Kara
2019-08-07 18:45 ` Bart Van Assche
2019-08-08 13:37 ` Jens Axboe
2019-07-30 10:16 ` Tetsuo Handa [this message]
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