From: Stanislav Brabec <sbrabec@suse.cz>
To: "Austin S. Hemmelgarn" <ahferroin7@gmail.com>,
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 20:31:43 +0100 [thread overview]
Message-ID: <56D0A81F.2050405@suse.cz> (raw)
In-Reply-To: <56D097D7.9020907@gmail.com>
On Feb 26, 2016 at 19:22 Austin S. Hemmelgarn wrote:
> The first commit is just test cases, and the others are specific issues
> that only affected BTRFS which have nothing to do with this thread at
> all other than involving mount(8) and BTRFS.
Yes, it is a bit off topic. It just demonstrates, how complex mount(8)
for btrfs is.
The test case is all-fail in util-linux 2.27.1.
> mount(8) behavior has the potential to cause either data
> corruption or similar behavior in the future (I would expect that XFS
> with metadata checksumming enabled would cause a similar interaction,
> although they probably would handle it better).
Especially "mount -a" has a hard time to recognize what was already
mounted and what still needs to be mounted.
The only information mount(8) has is the one from mountinfo.
Interpreting of the mountinfo contents to reconstruct possible mount
options used is a task far from being trivial.
Some of them are even impossible to discriminate:
Suppose you have:
mount -osubvol=/ /dev/sda2 /mnt/1
mount -osubvol=/sbv /dev/sda2 /mnt/2
Case 1:
mount -obind /mnt/1/sbv/bnd /mnt/3
Case 2:
mount -obind /mnt/2/bnd /mnt/3
Case 1 and case 2 have exactly the same mountinfo, but different
reference counts for /mnt/1 and /mnt/2.
--
Best Regards / S pozdravem,
Stanislav Brabec
software developer
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next prev parent reply other threads:[~2016-02-26 19:31 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 [this message]
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
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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