From: Theodore Ts'o <tytso@mit.edu>
To: Maxim Malkov <malkov@ispras.ru>
Cc: linux-ext4@vger.kernel.org, Andrey Tsyvarev <tsyvarev@ispras.ru>,
Alexey Khoroshilov <khoroshilov@ispras.ru>
Subject: Re: Online resizing of filesystem mounted with backup superblock causes corruption
Date: Wed, 24 Dec 2014 17:33:16 -0500 [thread overview]
Message-ID: <20141224223316.GD29088@thunk.org> (raw)
In-Reply-To: <5499ED8A.5010907@ispras.ru>
On Wed, Dec 24, 2014 at 01:32:42AM +0300, Maxim Malkov wrote:
> # mkfs.ext4 /dev/loop0 100M # adjust if necessary, should be less than
> partition size
>
> Superblock backups stored on blocks:
> 8193, 24577, 40961, 57345, 73729
> (pick one)
>
> # mount -t ext4 -o sb=40961 /dev/loop0 /media/
> # resize2fs /dev/loop0
> resize2fs 1.42.12 (29-Aug-2014)
> Filesystem at /dev/loop0 is mounted on /media; on-line resizing required
> old_desc_blocks = 1, new_desc_blocks = 4
>
> Now, depending on your luck, various things may happen. resize2fs may hang.
> You might see BUG() in your dmesg. Either way, system will become
> severely corrupted (as indicated by fsck). You won't be able to mount
> it, either.
Thanks for the bug report; I've can reproduce this using a 3.18 based
kernel.
It may be that simplest bug fix is to simply disallow resizing if we
are using a backup superblock.
- Ted
next prev parent reply other threads:[~2014-12-24 22:33 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-23 22:32 Online resizing of filesystem mounted with backup superblock causes corruption Maxim Malkov
2014-12-24 22:33 ` Theodore Ts'o [this message]
2014-12-27 4:59 ` [PATCH] ext4: prevent online resize with backup superblock Theodore Ts'o
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