From: Stanislav Brabec <sbrabec@suse.cz>
To: Al Viro <viro@ZenIV.linux.org.uk>,
"Austin S. Hemmelgarn" <ahferroin7@gmail.com>
Cc: linux-kernel@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
Btrfs BTRFS <linux-btrfs@vger.kernel.org>,
David Sterba <dsterba@suse.cz>
Subject: Re: loop subsystem corrupted after mounting multiple btrfs sub-volumes
Date: Fri, 26 Feb 2016 22:00:44 +0100 [thread overview]
Message-ID: <56D0BCFC.5020302@suse.cz> (raw)
In-Reply-To: <20160226203010.GD17997@ZenIV.linux.org.uk>
On Feb 26, 2016 at 21:30 Al Viro wrote:
> IMO on-demand losetup a-la -o loop is simply a bad idea...
So the correct behavior of -o loop should:
Check, whether another mount command already did losetup.
If not, allocate new loop device.
If yes, reuse existing loop device.
Well, it seems to be safe, even if the loop device was not allocated by
mount(8) itself, as
ioctl(fd, LOOP_CLR_FD)
never returns EBUSY:
# losetup /dev/loop2 /ext4.img
# mount /dev/loop2 /mnt
# strace losetup -d /dev/loop2 2>&1 | tail -n7 | head -n3
open("/dev/loop2", O_RDONLY|O_CLOEXEC) = 3
ioctl(3, LOOP_CLR_FD) = 0
close(3) = 0
If the recycling "alien" loop devices will not be considered as a good
idea, then (if possible):
If the loop device was allocated by mount(8) itself, recycle it.
If the loop device was not allocated by mount(8) itself, return error.
--
Best Regards / S pozdravem,
Stanislav Brabec
software developer
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next prev parent reply other threads:[~2016-02-26 21:00 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-25 19:22 loop subsystem corrupted after mounting multiple btrfs sub-volumes Stanislav Brabec
2016-02-26 12:33 ` Austin S. Hemmelgarn
2016-02-26 15:50 ` Stanislav Brabec
2016-02-26 16:39 ` Austin S. Hemmelgarn
2016-02-26 17:07 ` Stanislav Brabec
2016-02-26 18:22 ` Austin S. Hemmelgarn
2016-02-26 19:31 ` Stanislav Brabec
2016-02-26 17:53 ` Al Viro
2016-02-26 19:12 ` Stanislav Brabec
2016-02-26 20:05 ` Austin S. Hemmelgarn
2016-02-26 20:30 ` Al Viro
2016-02-26 20:36 ` Austin S. Hemmelgarn
2016-02-26 21:00 ` Stanislav Brabec [this message]
2016-02-26 22:00 ` Valdis.Kletnieks
2016-02-29 14:56 ` Stanislav Brabec
2016-03-01 13:44 ` Ming Lei
2016-04-12 18:38 ` Stanislav Brabec
2016-02-26 20:37 ` Stanislav Brabec
2016-02-26 21:03 ` Al Viro
2016-02-26 21:36 ` Stanislav Brabec
2016-02-26 21:45 ` Al Viro
2016-02-29 13:11 ` Austin S. Hemmelgarn
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