From mboxrd@z Thu Jan 1 00:00:00 1970
From: bugzilla-daemon@bugzilla.kernel.org
Subject: [Bug 42723] EXT4-fs error: ext4_mb_generate_buddy
Date: Tue, 30 Oct 2012 20:55:49 +0000 (UTC)
Message-ID: <20121030205549.37B6F11FB59@bugzilla.kernel.org>
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https://bugzilla.kernel.org/show_bug.cgi?id=42723
Theodore Tso changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
CC| |tytso@mit.edu
Resolution| |PATCH_ALREADY_AVAILABLE
--- Comment #8 from Theodore Tso 2012-10-30 20:55:48 ---
I'm pretty sure the bug the user was seeing is the one which was introduced in
3.2, and was fixed by commit b0dd6b70f0fd, which landed in 3.5, and then
backported to 3.2.20 and 3.4.3.
Birger first saw it in 3.2, and fell back to 3.1.7 where he didn't see it. And
the symptoms matched up. So that's almost certainly it. Note: the file system
wasn't actually corrupted at all; ext4 was just confused. :-)
commit b0dd6b70f0fda17ae9762fbb72d98e40a4f66556
Author: Theodore Ts'o
Date: Thu Jun 7 18:56:06 2012 -0400
ext4: fix the free blocks calculation for ext3 file systems w/ uninit_bg
Ext3 filesystems that are converted to use as many ext4 file system
features as possible will enable uninit_bg to speed up e2fsck times.
These file systems will have a native ext3 layout of inode tables and
block allocation bitmaps (as opposed to ext4's flex_bg layout).
Unfortunately, in these cases, when first allocating a block in an
uninitialized block group, ext4 would incorrectly calculate the number
of free blocks in that block group, and then errorneously report that
the file system was corrupt:
EXT4-fs error (device vdd): ext4_mb_generate_buddy:741: group 30, 32254
clusters in bitmap, 3
This problem can be reproduced via:
mke2fs -q -t ext4 -O ^flex_bg /dev/vdd 5g
mount -t ext4 /dev/vdd /mnt
fallocate -l 4600m /mnt/test
The problem was caused by a bone headed mistake in the check to see if a
particular metadata block was part of the block group.
Many thanks to Kees Cook for finding and bisecting the buggy commit
which introduced this bug (commit fd034a84e1, present since v3.2).
Reported-by: Sander Eikelenboom
Reported-by: Kees Cook
Signed-off-by: "Theodore Ts'o"
Tested-by: Kees Cook
Cc: stable@kernel.org
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