From: Maciej Żenczykowski <zenczykowski@gmail.com>
Date: Thu, 28 Oct 2010 01:30:06 +0000 (-0400)
Subject: ext4: don't update sb journal_devnum when RO dev
X-Git-Tag: v2.6.37-rc1~76^2^2~34
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c41303ced67c4ebf51bf2e7d0f139155e09e0939;p=pandora-kernel.git

ext4: don't update sb journal_devnum when RO dev

An ext4 filesystem on a read-only device, with an external journal
which is at a different device number then recorded in the superblock
will fail to honor the read-only setting of the device and trigger
a superblock update (write).

For example:
  - ext4 on a software raid which is in read-only mode
  - external journal on a read-write device which has changed device num
  - attempt to mount with -o journal_dev=<new_number>
  - hits BUG_ON(mddev->ro = 1) in md.c

Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Maciej Żenczykowski <zenczykowski@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
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