ocfs2: return -EROFS when filesystem becomes read-only

We should return -EROFS rather than other errno if filesystem becomes
read-only.

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/5B191B26.9010501@huawei.com


Signed-off-by: Jun Piao <piaojun@huawei.com>
Reviewed-by: Yiwen Jiang <jiangyiwen@huawei.com>
Acked-by: Joseph Qi <jiangqi903@gmail.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <ge.changwei@h3c.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>