tree 6593e7d580d48c2229df94bac0412654a1a7f76e
parent 2407518de63a2f80d9b850fb525f35df93bbbe53
author Maciej Żenczykowski <zenczykowski@gmail.com> 1288229406 -0400
committer Theodore Ts'o <tytso@mit.edu> 1288229406 -0400

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>