Don't try to make md arrays dirty if that is not meaningful.

Arrays personalities such as 'raid0' and 'linear' have no redundancy,
and so marking them as 'clean' or 'dirty' is not meaningful.
So always allow write requests without requiring a superblock update.

Such arrays types are detected by ->sync_request being NULL.  If it is
not possible to send a sync request we don't need a 'dirty' flag because
all a dirty flag does is trigger some sync_requests.

Signed-off-by: Neil Brown <neilb@suse.de>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 97852099defda678291bfa24d99e38349be466bf..9e3ce432e37e9936583223a9b54e77834b809bed 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5536,6 +5536,8 @@ void md_allow_write(mddev_t *mddev)
                return;
        if (mddev->ro)
                return;
+       if (!mddev->pers->sync_request)
+               return;
 
        spin_lock_irq(&mddev->write_lock);
        if (mddev->in_sync) {