blk: generic dispatch queue

Index: blk-fixes/drivers/block/elevator.c
===================================================================
@@ -40,6 +40,11 @@
 static DEFINE_SPINLOCK(elv_list_lock);
 static LIST_HEAD(elv_list);
 
+static inline sector_t rq_last_sector(struct request *rq)
+{
+	return rq->sector + rq->nr_sectors;
+}
+
 /*
  * can we safely merge with this request?
  */

@@ -143,6 +148,9 @@ static int elevator_attach(request_queue
 	INIT_LIST_HEAD(&q->queue_head);
 	q->last_merge = NULL;
 	q->elevator = eq;
+	q->last_sector = 0;
+	q->boundary_rq = NULL;
+	q->max_back_kb = 0;
 
 	if (eq->ops->elevator_init_fn)
 		ret = eq->ops->elevator_init_fn(q, eq);

@@ -225,6 +233,48 @@ void elevator_exit(elevator_t *e)
 	kfree(e);
 }
 
+/*
+ * Insert rq into dispatch queue of q.  Queue lock must be held on
+ * entry.  If sort != 0, rq is sort-inserted; otherwise, rq will be
+ * appended to the dispatch queue.  To be used by specific elevators.
+ */
+void elv_dispatch_insert(request_queue_t *q, struct request *rq, int sort)
+{
+	sector_t boundary;
+	unsigned max_back;
+	struct list_head *entry;
+
+	if (!sort) {
+		/* Specific elevator is performing sort.  Step away. */
+		q->last_sector = rq_last_sector(rq);
+		q->boundary_rq = rq;
+		list_add_tail(&rq->queuelist, &q->queue_head);
+		return;
+	}
+
+	boundary = q->last_sector;
+	max_back = q->max_back_kb * 2;
+	boundary = boundary > max_back ? boundary - max_back : 0;
+
+	list_for_each_prev(entry, &q->queue_head) {
+		struct request *pos = list_entry_rq(entry);
+
+		if (pos->flags & (REQ_SOFTBARRIER|REQ_HARDBARRIER|REQ_STARTED))
+			break;
+		if (rq->sector >= boundary) {
+			if (pos->sector < boundary)
+				continue;
+		} else {
+			if (pos->sector >= boundary)
+				break;
+		}
+		if (rq->sector >= pos->sector)
+			break;
+	}
+
+	list_add(&rq->queuelist, entry);
+}
+
 int elv_merge(request_queue_t *q, struct request **req, struct bio *bio)
 {
 	elevator_t *e = q->elevator;

@@ -255,13 +305,7 @@ void elv_merge_requests(request_queue_t 
 		e->ops->elevator_merge_req_fn(q, rq, next);
 }
 
-/*
- * For careful internal use by the block layer. Essentially the same as
- * a requeue in that it tells the io scheduler that this request is not
- * active in the driver or hardware anymore, but we don't want the request
- * added back to the scheduler. Function is not exported.
- */
-void elv_deactivate_request(request_queue_t *q, struct request *rq)
+void elv_requeue_request(request_queue_t *q, struct request *rq)
 {
 	elevator_t *e = q->elevator;
 

@@ -269,19 +313,14 @@ void elv_deactivate_request(request_queu
 	 * it already went through dequeue, we need to decrement the
 	 * in_flight count again
 	 */
-	if (blk_account_rq(rq))
+	if (blk_account_rq(rq)) {
 		q->in_flight--;
+		if (blk_sorted_rq(rq) && e->ops->elevator_deactivate_req_fn)
+			e->ops->elevator_deactivate_req_fn(q, rq);
+	}
 
 	rq->flags &= ~REQ_STARTED;
 
-	if (e->ops->elevator_deactivate_req_fn)
-		e->ops->elevator_deactivate_req_fn(q, rq);
-}
-
-void elv_requeue_request(request_queue_t *q, struct request *rq)
-{
-	elv_deactivate_request(q, rq);
-
 	/*
 	 * if this is the flush, requeue the original instead and drop the flush
 	 */

@@ -290,55 +329,89 @@ void elv_requeue_request(request_queue_t
 		rq = rq->end_io_data;
 	}
 
-	/*
-	 * the request is prepped and may have some resources allocated.
-	 * allowing unprepped requests to pass this one may cause resource
-	 * deadlock.  turn on softbarrier.
-	 */
-	rq->flags |= REQ_SOFTBARRIER;
-
-	/*
-	 * if iosched has an explicit requeue hook, then use that. otherwise
-	 * just put the request at the front of the queue
-	 */
-	if (q->elevator->ops->elevator_requeue_req_fn)
-		q->elevator->ops->elevator_requeue_req_fn(q, rq);
-	else
-		__elv_add_request(q, rq, ELEVATOR_INSERT_FRONT, 0);
+	__elv_add_request(q, rq, ELEVATOR_INSERT_FRONT, 0);
 }
 
 void __elv_add_request(request_queue_t *q, struct request *rq, int where,
 		       int plug)
 {
-	/*
-	 * barriers implicitly indicate back insertion
-	 */
-	if (rq->flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER) &&
-	    where == ELEVATOR_INSERT_SORT)
-		where = ELEVATOR_INSERT_BACK;
+	if (rq->flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)) {
+		/*
+		 * barriers implicitly indicate back insertion
+		 */
+		if (where == ELEVATOR_INSERT_SORT)
+			where = ELEVATOR_INSERT_BACK;
+
+		/*
+		 * this request is scheduling boundary, update last_sector
+		 */
+		if (blk_fs_request(rq)) {
+			q->last_sector = rq_last_sector(rq);
+			q->boundary_rq = rq;
+		}
+	}
 
 	if (plug)
 		blk_plug_device(q);
 
 	rq->q = q;
 
-	if (!test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags)) {
-		q->elevator->ops->elevator_add_req_fn(q, rq, where);
-
-		if (blk_queue_plugged(q)) {
-			int nrq = q->rq.count[READ] + q->rq.count[WRITE]
-				  - q->in_flight;
-
-			if (nrq >= q->unplug_thresh)
-				__generic_unplug_device(q);
-		}
-	} else
+	if (unlikely(test_bit(QUEUE_FLAG_DRAIN, &q->queue_flags))) {
 		/*
 		 * if drain is set, store the request "locally". when the drain
 		 * is finished, the requests will be handed ordered to the io
 		 * scheduler
 		 */
 		list_add_tail(&rq->queuelist, &q->drain_list);
+		return;
+	}
+
+	switch (where) {
+	case ELEVATOR_INSERT_FRONT:
+		rq->flags |= REQ_SOFTBARRIER;
+
+		list_add(&rq->queuelist, &q->queue_head);
+		break;
+
+	case ELEVATOR_INSERT_BACK:
+		rq->flags |= REQ_SOFTBARRIER;
+
+		while (q->elevator->ops->elevator_dispatch_fn(q, 1))
+			;
+		list_add_tail(&rq->queuelist, &q->queue_head);
+		/*
+		 * We kick the queue here for the following reasons.
+		 * - The elevator might have returned NULL previously
+		 *   to delay requests and returned them now.  As the
+		 *   queue wasn't empty before this request, ll_rw_blk
+		 *   won't run the queue on return, resulting in hang.
+		 * - Usually, back inserted requests won't be merged
+		 *   with anything.  There's no point in delaying queue
+		 *   processing.
+		 */
+		blk_remove_plug(q);
+		q->request_fn(q);
+		break;
+
+	case ELEVATOR_INSERT_SORT:
+		BUG_ON(!blk_fs_request(rq));
+		rq->flags |= REQ_SORTED;
+		q->elevator->ops->elevator_add_req_fn(q, rq);
+		break;
+
+	default:
+		printk(KERN_ERR "%s: bad insertion point %d\n",
+		       __FUNCTION__, where);
+		BUG();
+	}
+
+	if (blk_queue_plugged(q)) {
+		int nrq = q->rq.count[READ] + q->rq.count[WRITE]
+			- q->in_flight;
+
+		if (nrq >= q->unplug_thresh)
+			__generic_unplug_device(q);
+	}
 }
 
 void elv_add_request(request_queue_t *q, struct request *rq, int where,

@@ -353,13 +426,19 @@ void elv_add_request(request_queue_t *q,
 
 static inline struct request *__elv_next_request(request_queue_t *q)
 {
-	struct request *rq = q->elevator->ops->elevator_next_req_fn(q);
+	struct request *rq;
+
+	if (unlikely(list_empty(&q->queue_head) &&
+		     !q->elevator->ops->elevator_dispatch_fn(q, 0)))
+		return NULL;
+
+	rq = list_entry_rq(q->queue_head.next);
 
 	/*
 	 * if this is a barrier write and the device has to issue a
 	 * flush sequence to support it, check how far we are
 	 */
-	if (rq && blk_fs_request(rq) && blk_barrier_rq(rq)) {
+	if (blk_fs_request(rq) && blk_barrier_rq(rq)) {
 		BUG_ON(q->ordered == QUEUE_ORDERED_NONE);
 
 		if (q->ordered == QUEUE_ORDERED_FLUSH &&

@@ -376,16 +455,34 @@ struct request *elv_next_request(request
 	int ret;
 
 	while ((rq = __elv_next_request(q)) != NULL) {
-		/*
-		 * just mark as started even if we don't start it, a request
-		 * that has been delayed should not be passed by new incoming
-		 * requests
-		 */
-		rq->flags |= REQ_STARTED;
+		if (!(rq->flags & REQ_STARTED)) {
+			elevator_t *e = q->elevator;
+
+			/*
+			 * This is the first time the device driver
+			 * sees this request (possibly after
+			 * requeueing).  Notify IO scheduler.
+			 */
+			if (blk_sorted_rq(rq) &&
+			    e->ops->elevator_activate_req_fn)
+				e->ops->elevator_activate_req_fn(q, rq);
+
+			/*
+			 * just mark as started even if we don't start
+			 * it, a request that has been delayed should
+			 * not be passed by new incoming requests
+			 */
+			rq->flags |= REQ_STARTED;
+		}
 
 		if (rq == q->last_merge)
 			q->last_merge = NULL;
 
+		if (!q->boundary_rq || q->boundary_rq == rq) {
+			q->last_sector = rq_last_sector(rq);
+			q->boundary_rq = NULL;
+		}
+
 		if ((rq->flags & REQ_DONTPREP) || !q->prep_rq_fn)
 			break;
 

@@ -396,9 +493,9 @@ struct request *elv_next_request(request
 			/*
 			 * the request may have been (partially) prepped.
 			 * we need to keep this request in the front to
-			 * avoid resource deadlock.  turn on softbarrier.
+			 * avoid resource deadlock.  REQ_STARTED will
+			 * prevent other fs requests from passing this one.
 			 */
-			rq->flags |= REQ_SOFTBARRIER;
 			rq = NULL;
 			break;
 		} else if (ret == BLKPREP_KILL) {

@@ -421,16 +518,16 @@ struct request *elv_next_request(request
 	return rq;
 }
 
-void elv_remove_request(request_queue_t *q, struct request *rq)
+void elv_dequeue_request(request_queue_t *q, struct request *rq)
 {
-	elevator_t *e = q->elevator;
+	BUG_ON(list_empty(&rq->queuelist));
+
+	list_del_init(&rq->queuelist);
 
 	/*
 	 * the time frame between a request being removed from the lists
 	 * and to it is freed is accounted as io that is in progress at
-	 * the driver side. note that we only account requests that the
-	 * driver has seen (REQ_STARTED set), to avoid false accounting
-	 * for request-request merges
+	 * the driver side.
 	 */
 	if (blk_account_rq(rq))
 		q->in_flight++;

@@ -444,19 +541,19 @@ void elv_remove_request(request_queue_t 
 	 */
 	if (rq == q->last_merge)
 		q->last_merge = NULL;
-
-	if (e->ops->elevator_remove_req_fn)
-		e->ops->elevator_remove_req_fn(q, rq);
 }
 
 int elv_queue_empty(request_queue_t *q)
 {
 	elevator_t *e = q->elevator;
 
+	if (!list_empty(&q->queue_head))
+		return 0;
+
 	if (e->ops->elevator_queue_empty_fn)
 		return e->ops->elevator_queue_empty_fn(q);
 
-	return list_empty(&q->queue_head);
+	return 1;
 }
 
 struct request *elv_latter_request(request_queue_t *q, struct request *rq)

@@ -528,11 +625,11 @@ void elv_completed_request(request_queue
 	/*
 	 * request is released from the driver, io must be done
 	 */
-	if (blk_account_rq(rq))
+	if (blk_account_rq(rq)) {
 		q->in_flight--;
-
-	if (e->ops->elevator_completed_req_fn)
-		e->ops->elevator_completed_req_fn(q, rq);
+		if (blk_sorted_rq(rq) && e->ops->elevator_completed_req_fn)
+			e->ops->elevator_completed_req_fn(q, rq);
+	}
 }
 
 int elv_register_queue(struct request_queue *q)

@@ -705,11 +802,12 @@ ssize_t elv_iosched_show(request_queue_t
 	return len;
 }
 
+EXPORT_SYMBOL(elv_dispatch_insert);
 EXPORT_SYMBOL(elv_add_request);
 EXPORT_SYMBOL(__elv_add_request);
 EXPORT_SYMBOL(elv_requeue_request);
 EXPORT_SYMBOL(elv_next_request);
-EXPORT_SYMBOL(elv_remove_request);
+EXPORT_SYMBOL(elv_dequeue_request);
 EXPORT_SYMBOL(elv_queue_empty);
 EXPORT_SYMBOL(elv_completed_request);
 EXPORT_SYMBOL(elevator_exit);

Index: blk-fixes/drivers/block/ll_rw_blk.c
===================================================================
@@ -353,6 +353,8 @@ static void blk_pre_flush_end_io(struct 
 	struct request *rq = flush_rq->end_io_data;
 	request_queue_t *q = rq->q;
 
+	elv_completed_request(q, flush_rq);
+
 	rq->flags |= REQ_BAR_PREFLUSH;
 
 	if (!flush_rq->errors)

@@ -369,6 +371,8 @@ static void blk_post_flush_end_io(struct
 	struct request *rq = flush_rq->end_io_data;
 	request_queue_t *q = rq->q;
 
+	elv_completed_request(q, flush_rq);
+
 	rq->flags |= REQ_BAR_POSTFLUSH;
 
 	q->end_flush_fn(q, flush_rq);

@@ -408,8 +412,6 @@ struct request *blk_start_pre_flush(requ
 	if (!list_empty(&rq->queuelist))
 		blkdev_dequeue_request(rq);
 
-	elv_deactivate_request(q, rq);
-
 	flush_rq->end_io_data = rq;
 	flush_rq->end_io = blk_pre_flush_end_io;
 

@@ -1040,6 +1042,7 @@ EXPORT_SYMBOL(blk_queue_invalidate_tags)
 static char *rq_flags[] = {
 	"REQ_RW",
 	"REQ_FAILFAST",
+	"REQ_SORTED",
 	"REQ_SOFTBARRIER",
 	"REQ_HARDBARRIER",
 	"REQ_CMD",

@@ -2454,6 +2457,8 @@ static void __blk_put_request(request_qu
 	if (unlikely(--req->ref_count))
 		return;
 
+	elv_completed_request(q, req);
+
 	req->rq_status = RQ_INACTIVE;
 	req->rl = NULL;
 

@@ -2464,8 +2469,6 @@ static void __blk_put_request(request_qu
 	if (rl) {
 		int rw = rq_data_dir(req);
 
-		elv_completed_request(q, req);
-
 		BUG_ON(!list_empty(&req->queuelist));
 
 		blk_free_request(q, req);

@@ -2475,14 +2478,14 @@ static void __blk_put_request(request_qu
 
 void blk_put_request(struct request *req)
 {
+	unsigned long flags;
+	request_queue_t *q = req->q;
+
 	/*
-	 * if req->rl isn't set, this request didnt originate from the
-	 * block layer, so it's safe to just disregard it
+	 * Gee, IDE calls in w/ NULL q.  Fix IDE and remove the
+	 * following if (q) test.
 	 */
-	if (req->rl) {
-		unsigned long flags;
-		request_queue_t *q = req->q;
-
+	if (q) {
 		spin_lock_irqsave(q->queue_lock, flags);
 		__blk_put_request(q, req);
 		spin_unlock_irqrestore(q->queue_lock, flags);

Index: blk-fixes/include/linux/blkdev.h
===================================================================
@@ -203,6 +203,7 @@ struct request {
 enum rq_flag_bits {
 	__REQ_RW,		/* not set, read. set, write */
 	__REQ_FAILFAST,		/* no low level driver retries */
+	__REQ_SORTED,		/* elevator knows about this request */
 	__REQ_SOFTBARRIER,	/* may not be passed by ioscheduler */
 	__REQ_HARDBARRIER,	/* may not be passed by drive either */
 	__REQ_CMD,		/* is a regular fs rw request */

@@ -235,6 +236,7 @@ enum rq_flag_bits {
 
 #define REQ_RW		(1 << __REQ_RW)
 #define REQ_FAILFAST	(1 << __REQ_FAILFAST)
+#define REQ_SORTED	(1 << __REQ_SORTED)
 #define REQ_SOFTBARRIER	(1 << __REQ_SOFTBARRIER)
 #define REQ_HARDBARRIER	(1 << __REQ_HARDBARRIER)
 #define REQ_CMD		(1 << __REQ_CMD)

@@ -333,6 +335,13 @@ struct request_queue
 	end_flush_fn		*end_flush_fn;
 
 	/*
+	 * Dispatch queue sorting
+	 */
+	sector_t		last_sector;
+	struct request		*boundary_rq;
+	unsigned int		max_back_kb;
+
+	/*
 	 * Auto-unplugging state
 	 */
 	struct timer_list	unplug_timer;

@@ -454,6 +463,7 @@ enum {
 #define blk_pm_request(rq)	\
 	((rq)->flags & (REQ_PM_SUSPEND | REQ_PM_RESUME))
 
+#define blk_sorted_rq(rq)	((rq)->flags & REQ_SORTED)
 #define blk_barrier_rq(rq)	((rq)->flags & REQ_HARDBARRIER)
 #define blk_barrier_preflush(rq)	((rq)->flags & REQ_BAR_PREFLUSH)
 #define blk_barrier_postflush(rq)	((rq)->flags & REQ_BAR_POSTFLUSH)

@@ -611,12 +621,7 @@ extern void end_request(struct request *
 
 static inline void blkdev_dequeue_request(struct request *req)
 {
-	BUG_ON(list_empty(&req->queuelist));
-
-	list_del_init(&req->queuelist);
-
-	if (req->rl)
-		elv_remove_request(req->q, req);
+	elv_dequeue_request(req->q, req);
 }
 
 /*

Index: blk-fixes/include/linux/elevator.h
===================================================================
@@ -8,18 +8,17 @@ typedef void (elevator_merge_req_fn) (re
 
 typedef void (elevator_merged_fn) (request_queue_t *, struct request *);
 
-typedef struct request *(elevator_next_req_fn) (request_queue_t *);
+typedef int (elevator_dispatch_fn) (request_queue_t *, int);
 
-typedef void (elevator_add_req_fn) (request_queue_t *, struct request *, int);
+typedef void (elevator_add_req_fn) (request_queue_t *, struct request *);
 typedef int (elevator_queue_empty_fn) (request_queue_t *);
-typedef void (elevator_remove_req_fn) (request_queue_t *, struct request *);
-typedef void (elevator_requeue_req_fn) (request_queue_t *, struct request *);
 typedef struct request *(elevator_request_list_fn) (request_queue_t *, struct request *);
 typedef void (elevator_completed_req_fn) (request_queue_t *, struct request *);
 typedef int (elevator_may_queue_fn) (request_queue_t *, int, struct bio *);
 
 typedef int (elevator_set_req_fn) (request_queue_t *, struct request *, struct bio *, int);
 typedef void (elevator_put_req_fn) (request_queue_t *, struct request *);
+typedef void (elevator_activate_req_fn) (request_queue_t *, struct request *);
 typedef void (elevator_deactivate_req_fn) (request_queue_t *, struct request *);
 
 typedef int (elevator_init_fn) (request_queue_t *, elevator_t *);

@@ -31,10 +30,9 @@ struct elevator_ops
 	elevator_merged_fn *elevator_merged_fn;
 	elevator_merge_req_fn *elevator_merge_req_fn;
 
-	elevator_next_req_fn *elevator_next_req_fn;
+	elevator_dispatch_fn *elevator_dispatch_fn;
 	elevator_add_req_fn *elevator_add_req_fn;
-	elevator_remove_req_fn *elevator_remove_req_fn;
-	elevator_requeue_req_fn *elevator_requeue_req_fn;
+	elevator_activate_req_fn *elevator_activate_req_fn;
 	elevator_deactivate_req_fn *elevator_deactivate_req_fn;
 
 	elevator_queue_empty_fn *elevator_queue_empty_fn;

@@ -81,15 +79,15 @@ struct elevator_queue
 /*
  * block elevator interface
  */
+extern void elv_dispatch_insert(request_queue_t *, struct request *, int);
 extern void elv_add_request(request_queue_t *, struct request *, int, int);
 extern void __elv_add_request(request_queue_t *, struct request *, int, int);
 extern int elv_merge(request_queue_t *, struct request **, struct bio *);
 extern void elv_merge_requests(request_queue_t *, struct request *,
 			       struct request *);
 extern void elv_merged_request(request_queue_t *, struct request *);
-extern void elv_remove_request(request_queue_t *, struct request *);
+extern void elv_dequeue_request(request_queue_t *, struct request *);
 extern void elv_requeue_request(request_queue_t *, struct request *);
-extern void elv_deactivate_request(request_queue_t *, struct request *);
 extern int elv_queue_empty(request_queue_t *);
 extern struct request *elv_next_request(struct request_queue *q);
 extern struct request *elv_former_request(request_queue_t *, struct request *);

Index: blk-fixes/drivers/block/as-iosched.c
===================================================================
@@ -98,7 +98,6 @@ struct as_data {
 
 	struct as_rq *next_arq[2];	/* next in sort order */
 	sector_t last_sector[2];	/* last REQ_SYNC & REQ_ASYNC sectors */
-	struct list_head *dispatch;	/* driver dispatch queue */
 	struct list_head *hash;		/* request hash */
 
 	unsigned long exit_prob;	/* probability a task will exit while

@@ -239,6 +238,25 @@ static struct io_context *as_get_io_cont
 	return ioc;
 }
 
+static void as_put_io_context(struct as_rq *arq)
+{
+	struct as_io_context *aic;
+
+	if (unlikely(!arq->io_context))
+		return;
+
+	aic = arq->io_context->aic;
+
+	if (arq->is_sync == REQ_SYNC && aic) {
+		spin_lock(&aic->lock);
+		set_bit(AS_TASK_IORUNNING, &aic->state);
+		aic->last_end_request = jiffies;
+		spin_unlock(&aic->lock);
+	}
+
+	put_io_context(arq->io_context);
+}
+
 /*
  * the back merge hash support functions
  */

@@ -950,23 +968,12 @@ static void as_completed_request(request
 
 	WARN_ON(!list_empty(&rq->queuelist));
 
-	if (arq->state == AS_RQ_PRESCHED) {
-		WARN_ON(arq->io_context);
-		goto out;
-	}
-
-	if (arq->state == AS_RQ_MERGED)
-		goto out_ioc;
-
 	if (arq->state != AS_RQ_REMOVED) {
 		printk("arq->state %d\n", arq->state);
 		WARN_ON(1);
 		goto out;
 	}
 
-	if (!blk_fs_request(rq))
-		goto out;
-
 	if (ad->changed_batch && ad->nr_dispatched == 1) {
 		kblockd_schedule_work(&ad->antic_work);
 		ad->changed_batch = 0;

@@ -1001,21 +1008,7 @@ static void as_completed_request(request
 		}
 	}
 
-out_ioc:
-	if (!arq->io_context)
-		goto out;
-
-	if (arq->is_sync == REQ_SYNC) {
-		struct as_io_context *aic = arq->io_context->aic;
-		if (aic) {
-			spin_lock(&aic->lock);
-			set_bit(AS_TASK_IORUNNING, &aic->state);
-			aic->last_end_request = jiffies;
-			spin_unlock(&aic->lock);
-		}
-	}
-
-	put_io_context(arq->io_context);
+	as_put_io_context(arq);
 out:
 	arq->state = AS_RQ_POSTSCHED;
 }

@@ -1052,68 +1045,6 @@ static void as_remove_queued_request(req
 }
 
 /*
- * as_remove_dispatched_request is called to remove a request which has gone
- * to the dispatch list.
- */
-static void as_remove_dispatched_request(request_queue_t *q, struct request *rq)
-{
-	struct as_rq *arq = RQ_DATA(rq);
-	struct as_io_context *aic;
-
-	if (!arq) {
-		WARN_ON(1);
-		return;
-	}
-
-	WARN_ON(arq->state != AS_RQ_DISPATCHED);
-	WARN_ON(ON_RB(&arq->rb_node));
-	if (arq->io_context && arq->io_context->aic) {
-		aic = arq->io_context->aic;
-		if (aic) {
-			WARN_ON(!atomic_read(&aic->nr_dispatched));
-			atomic_dec(&aic->nr_dispatched);
-		}
-	}
-}
-
-/*
- * as_remove_request is called when a driver has finished with a request.
- * This should be only called for dispatched requests, but for some reason
- * a POWER4 box running hwscan it does not.
- */
-static void as_remove_request(request_queue_t *q, struct request *rq)
-{
-	struct as_rq *arq = RQ_DATA(rq);
-
-	if (unlikely(arq->state == AS_RQ_NEW))
-		goto out;
-
-	if (ON_RB(&arq->rb_node)) {
-		if (arq->state != AS_RQ_QUEUED) {
-			printk("arq->state %d\n", arq->state);
-			WARN_ON(1);
-			goto out;
-		}
-		/*
-		 * We'll lose the aliased request(s) here. I don't think this
-		 * will ever happen, but if it does, hopefully someone will
-		 * report it.
-		 */
-		WARN_ON(!list_empty(&rq->queuelist));
-		as_remove_queued_request(q, rq);
-	} else {
-		if (arq->state != AS_RQ_DISPATCHED) {
-			printk("arq->state %d\n", arq->state);
-			WARN_ON(1);
-			goto out;
-		}
-		as_remove_dispatched_request(q, rq);
-	}
-out:
-	arq->state = AS_RQ_REMOVED;
-}
-
-/*
  * as_fifo_expired returns 0 if there are no expired reads on the fifo,
  * 1 otherwise.  It is ratelimited so that we only perform the check once per
  * `fifo_expire' interval.  Otherwise a large number of expired requests

@@ -1162,10 +1093,9 @@ static inline int as_batch_expired(struc
 /*
  * move an entry to dispatch queue
  */
-static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq)
+static void as_move_to_dispatch(struct as_data *ad, struct as_rq *arq, int force)
 {
 	struct request *rq = arq->request;
-	struct list_head *insert;
 	const int data_dir = arq->is_sync;
 
 	BUG_ON(!ON_RB(&arq->rb_node));

@@ -1198,13 +1128,13 @@ static void as_move_to_dispatch(struct a
 	/*
 	 * take it off the sort and fifo list, add to dispatch queue
 	 */
-	insert = ad->dispatch->prev;
-
 	while (!list_empty(&rq->queuelist)) {
 		struct request *__rq = list_entry_rq(rq->queuelist.next);
 		struct as_rq *__arq = RQ_DATA(__rq);
 
-		list_move_tail(&__rq->queuelist, ad->dispatch);
+		list_del(&__rq->queuelist);
+
+		elv_dispatch_insert(ad->q, __rq, force);
 
 		if (__arq->io_context && __arq->io_context->aic)
 			atomic_inc(&__arq->io_context->aic->nr_dispatched);

@@ -1218,7 +1148,8 @@ static void as_move_to_dispatch(struct a
 	as_remove_queued_request(ad->q, rq);
 	WARN_ON(arq->state != AS_RQ_QUEUED);
 
-	list_add(&rq->queuelist, insert);
+	elv_dispatch_insert(ad->q, rq, force);
+
 	arq->state = AS_RQ_DISPATCHED;
 	if (arq->io_context && arq->io_context->aic)
 		atomic_inc(&arq->io_context->aic->nr_dispatched);

@@ -1230,12 +1161,42 @@ static void as_move_to_dispatch(struct a
  * read/write expire, batch expire, etc, and moves it to the dispatch
  * queue. Returns 1 if a request was found, 0 otherwise.
  */
-static int as_dispatch_request(struct as_data *ad)
+static int as_dispatch_request(request_queue_t *q, int force)
 {
+	struct as_data *ad = q->elevator->elevator_data;
 	struct as_rq *arq;
 	const int reads = !list_empty(&ad->fifo_list[REQ_SYNC]);
 	const int writes = !list_empty(&ad->fifo_list[REQ_ASYNC]);
 
+	if (unlikely(force)) {
+		/*
+		 * Forced dispatch, accounting is useless.  Reset
+		 * accounting states and dump fifo_lists.  Note that
+		 * batch_data_dir is reset to REQ_SYNC to avoid
+		 * screwing write batch accounting as write batch
+		 * accounting occurs on W->R transition.
+		 */
+		int dispatched = 0;
+
+		ad->batch_data_dir = REQ_SYNC;
+		ad->changed_batch = 0;
+		ad->new_batch = 0;
+
+		while (ad->next_arq[REQ_SYNC]) {
+			as_move_to_dispatch(ad, ad->next_arq[REQ_SYNC], 1);
+			dispatched++;
+		}
+		ad->last_check_fifo[REQ_SYNC] = jiffies;
+
+		while (ad->next_arq[REQ_ASYNC]) {
+			as_move_to_dispatch(ad, ad->next_arq[REQ_ASYNC], 1);
+			dispatched++;
+		}
+		ad->last_check_fifo[REQ_ASYNC] = jiffies;
+
+		return dispatched;
+	}
+
 	/* Signal that the write batch was uncontended, so we can't time it */
 	if (ad->batch_data_dir == REQ_ASYNC && !reads) {
 		if (ad->current_write_count == 0 || !writes)

@@ -1354,25 +1315,11 @@ fifo_expired:
 	/*
 	 * arq is the selected appropriate request.
 	 */
-	as_move_to_dispatch(ad, arq);
+	as_move_to_dispatch(ad, arq, 0);
 
 	return 1;
 }
 
-static struct request *as_next_request(request_queue_t *q)
-{
-	struct as_data *ad = q->elevator->elevator_data;
-	struct request *rq = NULL;
-
-	/*
-	 * if there are still requests on the dispatch queue, grab the first
-	 */
-	if (!list_empty(ad->dispatch) || as_dispatch_request(ad))
-		rq = list_entry_rq(ad->dispatch->next);
-
-	return rq;
-}
-
 /*
  * Add arq to a list behind alias
  */

@@ -1410,11 +1357,19 @@ as_add_aliased_request(struct as_data *a
 /*
  * add arq to rbtree and fifo
  */
-static void as_add_request(struct as_data *ad, struct as_rq *arq)
+static void as_add_request(request_queue_t *q, struct request *rq)
 {
+	struct as_data *ad = q->elevator->elevator_data;
+	struct as_rq *arq = RQ_DATA(rq);
 	struct as_rq *alias;
 	int data_dir;
 
+	if (arq->state != AS_RQ_PRESCHED) {
+		printk("arq->state: %d\n", arq->state);
+		WARN_ON(1);
+	}
+	arq->state = AS_RQ_NEW;
+
 	if (rq_data_dir(arq->request) == READ
 			|| current->flags&PF_SYNCWRITE)
 		arq->is_sync = 1;

@@ -1463,96 +1418,24 @@ static void as_add_request(struct as_dat
 	arq->state = AS_RQ_QUEUED;
 }
 
-static void as_deactivate_request(request_queue_t *q, struct request *rq)
+static void as_activate_request(request_queue_t *q, struct request *rq)
 {
-	struct as_data *ad = q->elevator->elevator_data;
 	struct as_rq *arq = RQ_DATA(rq);
 
-	if (arq) {
-		if (arq->state == AS_RQ_REMOVED) {
-			arq->state = AS_RQ_DISPATCHED;
-			if (arq->io_context && arq->io_context->aic)
-				atomic_inc(&arq->io_context->aic->nr_dispatched);
-		}
-	} else
-		WARN_ON(blk_fs_request(rq)
-			&& (!(rq->flags & (REQ_HARDBARRIER|REQ_SOFTBARRIER))) );
-
-	/* Stop anticipating - let this request get through */
-	as_antic_stop(ad);
-}
-
-/*
- * requeue the request. The request has not been completed, nor is it a
- * new request, so don't touch accounting.
- */
-static void as_requeue_request(request_queue_t *q, struct request *rq)
-{
-	as_deactivate_request(q, rq);
-	list_add(&rq->queuelist, &q->queue_head);
-}
-
-/*
- * Account a request that is inserted directly onto the dispatch queue.
- * arq->io_context->aic->nr_dispatched should not need to be incremented
- * because only new requests should come through here: requeues go through
- * our explicit requeue handler.
- */
-static void as_account_queued_request(struct as_data *ad, struct request *rq)
-{
-	if (blk_fs_request(rq)) {
-		struct as_rq *arq = RQ_DATA(rq);
-		arq->state = AS_RQ_DISPATCHED;
-		ad->nr_dispatched++;
-	}
+	WARN_ON(arq->state != AS_RQ_DISPATCHED);
+	arq->state = AS_RQ_REMOVED;
+	if (arq->io_context && arq->io_context->aic)
+		atomic_dec(&arq->io_context->aic->nr_dispatched);
 }
 
-static void
-as_insert_request(request_queue_t *q, struct request *rq, int where)
+static void as_deactivate_request(request_queue_t *q, struct request *rq)
 {
-	struct as_data *ad = q->elevator->elevator_data;
 	struct as_rq *arq = RQ_DATA(rq);
 
-	if (arq) {
-		if (arq->state != AS_RQ_PRESCHED) {
-			printk("arq->state: %d\n", arq->state);
-			WARN_ON(1);
-		}
-		arq->state = AS_RQ_NEW;
-	}
-
-	/* barriers must flush the reorder queue */
-	if (unlikely(rq->flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)
-			&& where == ELEVATOR_INSERT_SORT)) {
-		WARN_ON(1);
-		where = ELEVATOR_INSERT_BACK;
-	}
-
-	switch (where) {
-		case ELEVATOR_INSERT_BACK:
-			while (ad->next_arq[REQ_SYNC])
-				as_move_to_dispatch(ad, ad->next_arq[REQ_SYNC]);
-
-			while (ad->next_arq[REQ_ASYNC])
-				as_move_to_dispatch(ad, ad->next_arq[REQ_ASYNC]);
-
-			list_add_tail(&rq->queuelist, ad->dispatch);
-			as_account_queued_request(ad, rq);
-			as_antic_stop(ad);
-			break;
-		case ELEVATOR_INSERT_FRONT:
-			list_add(&rq->queuelist, ad->dispatch);
-			as_account_queued_request(ad, rq);
-			as_antic_stop(ad);
-			break;
-		case ELEVATOR_INSERT_SORT:
-			BUG_ON(!blk_fs_request(rq));
-			as_add_request(ad, arq);
-			break;
-		default:
-			BUG();
-			return;
-	}
+	WARN_ON(arq->state != AS_RQ_REMOVED);
+	arq->state = AS_RQ_DISPATCHED;
+	if (arq->io_context && arq->io_context->aic)
+		atomic_inc(&arq->io_context->aic->nr_dispatched);
 }
 
 /*

@@ -1565,12 +1448,8 @@ static int as_queue_empty(request_queue_
 {
 	struct as_data *ad = q->elevator->elevator_data;
 
-	if (!list_empty(&ad->fifo_list[REQ_ASYNC])
-		|| !list_empty(&ad->fifo_list[REQ_SYNC])
-		|| !list_empty(ad->dispatch))
-			return 0;
-
-	return 1;
+	return list_empty(&ad->fifo_list[REQ_ASYNC])
+		&& list_empty(&ad->fifo_list[REQ_SYNC]);
 }
 
 static struct request *

@@ -1763,6 +1642,7 @@ as_merged_requests(request_queue_t *q, s
 	 * kill knowledge of next, this one is a goner
 	 */
 	as_remove_queued_request(q, next);
+	as_put_io_context(anext);
 
 	anext->state = AS_RQ_MERGED;
 }

@@ -1782,7 +1662,7 @@ static void as_work_handler(void *data)
 	unsigned long flags;
 
 	spin_lock_irqsave(q->queue_lock, flags);
-	if (as_next_request(q))
+	if (!as_queue_empty(q))
 		q->request_fn(q);
 	spin_unlock_irqrestore(q->queue_lock, flags);
 }

@@ -1797,7 +1677,9 @@ static void as_put_request(request_queue
 		return;
 	}
 
-	if (arq->state != AS_RQ_POSTSCHED && arq->state != AS_RQ_PRESCHED) {
+	if (unlikely(arq->state != AS_RQ_POSTSCHED &&
+		     arq->state != AS_RQ_PRESCHED &&
+		     arq->state != AS_RQ_MERGED)) {
 		printk("arq->state %d\n", arq->state);
 		WARN_ON(1);
 	}

@@ -1907,7 +1789,6 @@ static int as_init_queue(request_queue_t
 	INIT_LIST_HEAD(&ad->fifo_list[REQ_ASYNC]);
 	ad->sort_list[REQ_SYNC] = RB_ROOT;
 	ad->sort_list[REQ_ASYNC] = RB_ROOT;
-	ad->dispatch = &q->queue_head;
 	ad->fifo_expire[REQ_SYNC] = default_read_expire;
 	ad->fifo_expire[REQ_ASYNC] = default_write_expire;
 	ad->antic_expire = default_antic_expire;

@@ -2072,10 +1953,9 @@ static struct elevator_type iosched_as =
 		.elevator_merge_fn = 		as_merge,
 		.elevator_merged_fn =		as_merged_request,
 		.elevator_merge_req_fn =	as_merged_requests,
-		.elevator_next_req_fn =		as_next_request,
-		.elevator_add_req_fn =		as_insert_request,
-		.elevator_remove_req_fn =	as_remove_request,
-		.elevator_requeue_req_fn = 	as_requeue_request,
+		.elevator_dispatch_fn =		as_dispatch_request,
+		.elevator_add_req_fn =		as_add_request,
+		.elevator_activate_req_fn =	as_activate_request,
 		.elevator_deactivate_req_fn = 	as_deactivate_request,
 		.elevator_queue_empty_fn =	as_queue_empty,
 		.elevator_completed_req_fn =	as_completed_request,

161 lines not on this page · raw message

Index: blk-fixes/drivers/block/noop-iosched.c
===================================================================
@@ -28,13 +28,9 @@ static void elevator_noop_merge_requests
 	list_del_init(&next->queuelist);
 }
 
-static void elevator_noop_add_request(request_queue_t *q, struct request *rq,
-				      int where)
+static void elevator_noop_add_request(request_queue_t *q, struct request *rq)
 {
-	if (where == ELEVATOR_INSERT_FRONT)
-		list_add(&rq->queuelist, &q->queue_head);
-	else
-		list_add_tail(&rq->queuelist, &q->queue_head);
+	elv_dispatch_insert(q, rq, 0);
 
 	/*
 	 * new merges must not precede this barrier

@@ -45,19 +41,16 @@ static void elevator_noop_add_request(re
 		q->last_merge = rq;
 }
 
-static struct request *elevator_noop_next_request(request_queue_t *q)
+static int elevator_noop_dispatch(request_queue_t *q, int force)
 {
-	if (!list_empty(&q->queue_head))
-		return list_entry_rq(q->queue_head.next);
-
-	return NULL;
+	return 0;
 }
 
 static struct elevator_type elevator_noop = {
 	.ops = {
 		.elevator_merge_fn		= elevator_noop_merge,
 		.elevator_merge_req_fn		= elevator_noop_merge_requests,
-		.elevator_next_req_fn		= elevator_noop_next_request,
+		.elevator_dispatch_fn		= elevator_noop_dispatch,
 		.elevator_add_req_fn		= elevator_noop_add_request,
 	},
 	.elevator_name = "noop",

549 lines not on this page · raw message

index 5720409..0c389a0 100644
@@ -652,13 +652,16 @@ void elv_unregister(struct elevator_type
 		struct io_context *ioc = p->io_context;
 		struct cfq_io_context *cic;
 
+		if (!ioc)
+			continue;
+
 		if (ioc->cic_root.rb_node != NULL) {
 			cic = rb_entry(rb_first(&ioc->cic_root), struct cfq_io_context, rb_node);
 			cic->exit(ioc);
 			cic->dtor(ioc);
 		}
 
-		if (ioc && ioc->aic) {
+		if (ioc->aic) {
 			ioc->aic->exit(ioc->aic);
 			ioc->aic->dtor(ioc->aic);
 			ioc->aic = NULL;

Index: blk-fixes/drivers/block/elevator.c
===================================================================
@@ -88,15 +88,6 @@ inline int elv_try_merge(struct request 
 }
 EXPORT_SYMBOL(elv_try_merge);
 
-inline int elv_try_last_merge(request_queue_t *q, struct bio *bio)
-{
-	if (q->last_merge)
-		return elv_try_merge(q->last_merge, bio);
-
-	return ELEVATOR_NO_MERGE;
-}
-EXPORT_SYMBOL(elv_try_last_merge);
-
 static struct elevator_type *elevator_find(const char *name)
 {
 	struct elevator_type *e = NULL;

@@ -244,6 +235,9 @@ void elv_dispatch_insert(request_queue_t
 	unsigned max_back;
 	struct list_head *entry;
 
+	if (q->last_merge == rq)
+		q->last_merge = NULL;
+
 	if (!sort) {
 		/* Specific elevator is performing sort.  Step away. */
 		q->last_sector = rq_last_sector(rq);

@@ -278,6 +272,15 @@ void elv_dispatch_insert(request_queue_t
 int elv_merge(request_queue_t *q, struct request **req, struct bio *bio)
 {
 	elevator_t *e = q->elevator;
+	int ret;
+
+	if (q->last_merge) {
+		ret = elv_try_merge(q->last_merge, bio);
+		if (ret != ELEVATOR_NO_MERGE) {
+			*req = q->last_merge;
+			return ret;
+		}
+	}
 
 	if (e->ops->elevator_merge_fn)
 		return e->ops->elevator_merge_fn(q, req, bio);

@@ -291,6 +294,8 @@ void elv_merged_request(request_queue_t 
 
 	if (e->ops->elevator_merged_fn)
 		e->ops->elevator_merged_fn(q, rq);
+
+	q->last_merge = rq;
 }
 
 void elv_merge_requests(request_queue_t *q, struct request *rq,

@@ -298,11 +303,10 @@ void elv_merge_requests(request_queue_t 
 {
 	elevator_t *e = q->elevator;
 
-	if (q->last_merge == next)
-		q->last_merge = NULL;
-
 	if (e->ops->elevator_merge_req_fn)
 		e->ops->elevator_merge_req_fn(q, rq, next);
+
+	q->last_merge = rq;
 }
 
 void elv_requeue_request(request_queue_t *q, struct request *rq)

@@ -397,6 +401,8 @@ void __elv_add_request(request_queue_t *
 		BUG_ON(!blk_fs_request(rq));
 		rq->flags |= REQ_SORTED;
 		q->elevator->ops->elevator_add_req_fn(q, rq);
+		if (q->last_merge == NULL && rq_mergeable(rq))
+			q->last_merge = rq;
 		break;
 
 	default:

@@ -475,9 +481,6 @@ struct request *elv_next_request(request
 			rq->flags |= REQ_STARTED;
 		}
 
-		if (rq == q->last_merge)
-			q->last_merge = NULL;
-
 		if (!q->boundary_rq || q->boundary_rq == rq) {
 			q->last_sector = rq_last_sector(rq);
 			q->boundary_rq = NULL;

@@ -531,16 +534,6 @@ void elv_dequeue_request(request_queue_t
 	 */
 	if (blk_account_rq(rq))
 		q->in_flight++;
-
-	/*
-	 * the main clearing point for q->last_merge is on retrieval of
-	 * request by driver (it calls elv_next_request()), but it _can_
-	 * also happen here if a request is added to the queue but later
-	 * deleted without ever being given to driver (merged with another
-	 * request).
-	 */
-	if (rq == q->last_merge)
-		q->last_merge = NULL;
 }
 
 int elv_queue_empty(request_queue_t *q)

Index: blk-fixes/drivers/block/as-iosched.c
===================================================================
@@ -279,14 +279,6 @@ static inline void as_del_arq_hash(struc
 		__as_del_arq_hash(arq);
 }
 
-static void as_remove_merge_hints(request_queue_t *q, struct as_rq *arq)
-{
-	as_del_arq_hash(arq);
-
-	if (q->last_merge == arq->request)
-		q->last_merge = NULL;
-}
-
 static void as_add_arq_hash(struct as_data *ad, struct as_rq *arq)
 {
 	struct request *rq = arq->request;

@@ -330,7 +322,7 @@ static struct request *as_find_arq_hash(
 		BUG_ON(!arq->on_hash);
 
 		if (!rq_mergeable(__rq)) {
-			as_remove_merge_hints(ad->q, arq);
+			as_del_arq_hash(arq);
 			continue;
 		}
 

@@ -1040,7 +1032,7 @@ static void as_remove_queued_request(req
 		ad->next_arq[data_dir] = as_find_next_arq(ad, arq);
 
 	list_del_init(&arq->fifo);
-	as_remove_merge_hints(q, arq);
+	as_del_arq_hash(arq);
 	as_del_arq_rb(ad, arq);
 }
 

@@ -1351,7 +1343,7 @@ as_add_aliased_request(struct as_data *a
 	/*
 	 * Don't want to have to handle merges.
 	 */
-	as_remove_merge_hints(ad->q, arq);
+	as_del_arq_hash(arq);
 }
 
 /*

@@ -1392,12 +1384,8 @@ static void as_add_request(request_queue
 		arq->expires = jiffies + ad->fifo_expire[data_dir];
 		list_add_tail(&arq->fifo, &ad->fifo_list[data_dir]);
 
-		if (rq_mergeable(arq->request)) {
+		if (rq_mergeable(arq->request))
 			as_add_arq_hash(ad, arq);
-
-			if (!ad->q->last_merge)
-				ad->q->last_merge = arq->request;
-		}
 		as_update_arq(ad, arq); /* keep state machine up to date */
 
 	} else {

@@ -1487,15 +1475,6 @@ as_merge(request_queue_t *q, struct requ
 	int ret;
 
 	/*
-	 * try last_merge to avoid going to hash
-	 */
-	ret = elv_try_last_merge(q, bio);
-	if (ret != ELEVATOR_NO_MERGE) {
-		__rq = q->last_merge;
-		goto out_insert;
-	}
-
-	/*
 	 * see if the merge hash can satisfy a back merge
 	 */
 	__rq = as_find_arq_hash(ad, bio->bi_sector);

@@ -1523,9 +1502,6 @@ as_merge(request_queue_t *q, struct requ
 
 	return ELEVATOR_NO_MERGE;
 out:
-	if (rq_mergeable(__rq))
-		q->last_merge = __rq;
-out_insert:
 	if (ret) {
 		if (rq_mergeable(__rq))
 			as_hot_arq_hash(ad, RQ_DATA(__rq));

@@ -1572,9 +1548,6 @@ static void as_merged_request(request_qu
 		 * behind the disk head. We currently don't bother adjusting.
 		 */
 	}
-
-	if (arq->on_hash)
-		q->last_merge = req;
 }
 
 static void

Index: blk-fixes/drivers/block/deadline-iosched.c
===================================================================
@@ -112,15 +112,6 @@ static inline void deadline_del_drq_hash
 		__deadline_del_drq_hash(drq);
 }
 
-static void
-deadline_remove_merge_hints(request_queue_t *q, struct deadline_rq *drq)
-{
-	deadline_del_drq_hash(drq);
-
-	if (q->last_merge == drq->request)
-		q->last_merge = NULL;
-}
-
 static inline void
 deadline_add_drq_hash(struct deadline_data *dd, struct deadline_rq *drq)
 {

@@ -299,12 +290,8 @@ deadline_add_request(struct request_queu
 	drq->expires = jiffies + dd->fifo_expire[data_dir];
 	list_add_tail(&drq->fifo, &dd->fifo_list[data_dir]);
 
-	if (rq_mergeable(rq)) {
+	if (rq_mergeable(rq))
 		deadline_add_drq_hash(dd, drq);
-
-		if (!q->last_merge)
-			q->last_merge = rq;
-	}
 }
 
 /*

@@ -316,8 +303,8 @@ static void deadline_remove_request(requ
 	struct deadline_data *dd = q->elevator->elevator_data;
 
 	list_del_init(&drq->fifo);
-	deadline_remove_merge_hints(q, drq);
 	deadline_del_drq_rb(dd, drq);
+	deadline_del_drq_hash(drq);
 }
 
 static int

@@ -328,15 +315,6 @@ deadline_merge(request_queue_t *q, struc
 	int ret;
 
 	/*
-	 * try last_merge to avoid going to hash
-	 */
-	ret = elv_try_last_merge(q, bio);
-	if (ret != ELEVATOR_NO_MERGE) {
-		__rq = q->last_merge;
-		goto out_insert;
-	}
-
-	/*
 	 * see if the merge hash can satisfy a back merge
 	 */
 	__rq = deadline_find_drq_hash(dd, bio->bi_sector);

@@ -368,8 +346,6 @@ deadline_merge(request_queue_t *q, struc
 
 	return ELEVATOR_NO_MERGE;
 out:
-	q->last_merge = __rq;
-out_insert:
 	if (ret)
 		deadline_hot_drq_hash(dd, RQ_DATA(__rq));
 	*req = __rq;

@@ -394,8 +370,6 @@ static void deadline_merged_request(requ
 		deadline_del_drq_rb(dd, drq);
 		deadline_add_drq_rb(dd, drq);
 	}
-
-	q->last_merge = req;
 }
 
 static void

Index: blk-fixes/drivers/block/noop-iosched.c
===================================================================
@@ -7,38 +7,9 @@
 #include <linux/module.h>
 #include <linux/init.h>
 
-/*
- * See if we can find a request that this buffer can be coalesced with.
- */
-static int elevator_noop_merge(request_queue_t *q, struct request **req,
-			       struct bio *bio)
-{
-	int ret;
-
-	ret = elv_try_last_merge(q, bio);
-	if (ret != ELEVATOR_NO_MERGE)
-		*req = q->last_merge;
-
-	return ret;
-}
-
-static void elevator_noop_merge_requests(request_queue_t *q, struct request *req,
-					 struct request *next)
-{
-	list_del_init(&next->queuelist);
-}
-
 static void elevator_noop_add_request(request_queue_t *q, struct request *rq)
 {
 	elv_dispatch_insert(q, rq, 0);
-
-	/*
-	 * new merges must not precede this barrier
-	 */
-	if (rq->flags & REQ_HARDBARRIER)
-		q->last_merge = NULL;
-	else if (!q->last_merge)
-		q->last_merge = rq;
 }
 
 static int elevator_noop_dispatch(request_queue_t *q, int force)

@@ -48,8 +19,6 @@ static int elevator_noop_dispatch(reques
 
 static struct elevator_type elevator_noop = {
 	.ops = {
-		.elevator_merge_fn		= elevator_noop_merge,
-		.elevator_merge_req_fn		= elevator_noop_merge_requests,
 		.elevator_dispatch_fn		= elevator_noop_dispatch,
 		.elevator_add_req_fn		= elevator_noop_add_request,
 	},

Index: blk-fixes/drivers/block/cfq-iosched.c
===================================================================
@@ -304,14 +304,6 @@ static inline void cfq_del_crq_hash(stru
 	hlist_del_init(&crq->hash);
 }
 
-static void cfq_remove_merge_hints(request_queue_t *q, struct cfq_rq *crq)
-{
-	cfq_del_crq_hash(crq);
-
-	if (q->last_merge == crq->request)
-		q->last_merge = NULL;
-}
-
 static inline void cfq_add_crq_hash(struct cfq_data *cfqd, struct cfq_rq *crq)
 {
 	const int hash_idx = CFQ_MHASH_FN(rq_hash_key(crq->request));

@@ -672,7 +664,7 @@ static void cfq_remove_request(struct re
 
 	list_del_init(&rq->queuelist);
 	cfq_del_crq_rb(crq);
-	cfq_remove_merge_hints(rq->q, crq);
+	cfq_del_crq_hash(crq);
 }
 
 static int

@@ -682,12 +674,6 @@ cfq_merge(request_queue_t *q, struct req
 	struct request *__rq;
 	int ret;
 
-	ret = elv_try_last_merge(q, bio);
-	if (ret != ELEVATOR_NO_MERGE) {
-		__rq = q->last_merge;
-		goto out_insert;
-	}
-
 	__rq = cfq_find_rq_hash(cfqd, bio->bi_sector);
 	if (__rq && elv_rq_merge_ok(__rq, bio)) {
 		ret = ELEVATOR_BACK_MERGE;

@@ -702,8 +688,6 @@ cfq_merge(request_queue_t *q, struct req
 
 	return ELEVATOR_NO_MERGE;
 out:
-	q->last_merge = __rq;
-out_insert:
 	*req = __rq;
 	return ret;
 }

@@ -722,8 +706,6 @@ static void cfq_merged_request(request_q
 		cfq_update_next_crq(crq);
 		cfq_reposition_crq_rb(cfqq, crq);
 	}
-
-	q->last_merge = req;
 }
 
 static void

@@ -1670,13 +1652,9 @@ static void cfq_insert_request(request_q
 
 	list_add_tail(&rq->queuelist, &cfqq->fifo);
 
-	if (rq_mergeable(rq)) {
+	if (rq_mergeable(rq))
 		cfq_add_crq_hash(cfqd, crq);
 
-		if (!cfqd->queue->last_merge)
-			cfqd->queue->last_merge = rq;
-	}
-
 	cfq_crq_enqueued(cfqd, cfqq, crq);
 }