From: Eric Sandeen <sandeen@redhat.com>
Date: Sun, 19 Aug 2012 02:29:40 +0000 (-0400)
Subject: jbd2: don't write superblock when if its empty
X-Git-Tag: v3.7-rc1~91^2~55
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=eeecef0af5ea4efd763c9554cf2bd80fc4a0efd3;p=pandora-kernel.git

jbd2: don't write superblock when if its empty

This sequence:

# truncate --size=1g fsfile
# mkfs.ext4 -F fsfile
# mount -o loop,ro fsfile /mnt
# umount /mnt
# dmesg | tail

results in an IO error when unmounting the RO filesystem:

[  318.020828] Buffer I/O error on device loop1, logical block 196608
[  318.027024] lost page write due to I/O error on loop1
[  318.032088] JBD2: Error -5 detected when updating journal superblock for loop1-8.

This was a regression introduced by commit 24bcc89c7e7c: "jbd2: split
updating of journal superblock and marking journal empty".

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
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