[PATCH] io scheduler oops fixes

Peter Osterlund <petero2@telia.com> notes oopses in the anticipatory
scheduler with slab poisoning enabled due to arq->rb_node.rb_right being
uninitialised.  So wipe the whole thing when we allocate it.

deadline seems to have the same problem.

drivers/block/as-iosched.c

@@ -1718,6 +1718,7 @@ static int as_set_request(request_queue_t *q, struct request *rq, int gfp_mask)
 	struct as_rq *arq = mempool_alloc(ad->arq_pool, gfp_mask);
 
 	if (arq) {
+		memset(arq, 0, sizeof(*arq));
 		RB_CLEAR(&arq->rb_node);
 		arq->request = rq;
 		arq->state = AS_RQ_NEW;

drivers/block/deadline-iosched.c

@@ -765,6 +765,7 @@ deadline_set_request(request_queue_t *q, struct request *rq, int gfp_mask)
 
 	drq = mempool_alloc(dd->drq_pool, gfp_mask);
 	if (drq) {
+		memset(drq, 0, sizeof(*drq));
 		RB_CLEAR(&drq->rb_node);
 		drq->request = rq;