When the in memory flag is changed, we need to persist the change in the
rdev superblock flags. This is needed for "writemostly" and "failfast".
Reviewed-by: NLi Feng <fengli@smartx.com>
Signed-off-by: NXiao Ni <xni@redhat.com>
Signed-off-by: NSong Liu <songliubraving@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>