md/raid5: add simple plugging infrastructure.
md/raid5 uses the plugging infrastructure provided by the block layer
and 'struct request_queue'. However when we plug raid5 under dm there
is no request queue so we cannot use that.
So create a similar infrastructure that is much lighter weight and use
it for raid5.
Signed-off-by: NeilBrown <neilb@suse.de>
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index d6470de..6acd458 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -398,6 +398,9 @@
* (fresh device added).
* Cleared when a sync completes.
*/
+
+ struct plug_handle plug;
+
/* per cpu variables */
struct raid5_percpu {
struct page *spare_page; /* Used when checking P/Q in raid6 */