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Date: Thu, 7 Jun 2012 18:54:46 -0400
From: "Ted Ts'o" <tytso@mit.edu>
To: Kees Cook <keescook@chromium.org>
Cc: djwong@us.ibm.com, Sander Eikelenboom <linux@eikelenboom.it>,
        Linus Torvalds <torvalds@linux-foundation.org>, dm-devel@redhat.com,
        linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [dm-devel] EXT4-fs error (device dm-42):
 ext4_mb_generate_buddy:741: group 1904, 32254 clusters in bitmap, 32258 in
 gd
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On Thu, Jun 07, 2012 at 03:40:40PM -0700, Kees Cook wrote:
> 
> FWIW, I was building the filesystem that triggered this as ext4:
> 
>   mkfs.ext4 -T default -m 0 -O ^huge_file,^flex_bg -E
> discard,lazy_itable_init /dev/mapper/...

Ouy of curiosity, was there a reason you chose those particular file
system parameters?  It's a surprising set, because if you're starting
with a fresh file system, enabling flex_bg produces a more optimal
file system layout.

The reason why I wrote the commit description way I did was because it
seemed to be the most likely way that someone would trip across this
bug.  We didn't notice this for as long as we did since most of the
users of ext4 (especially those who use community distributions) have
been using freshly mkfs'ed ext4 file systems.

						- Ted
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