[PATCH] 01/05 Implement generic dispatch queue

Implements generic dispatch queue which can replace all
dispatch queues implemented by each iosched.  This reduces
code duplication, eases enforcing semantics over dispatch
queue, and simplifies specific ioscheds.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jens Axboe <axboe@suse.de>

drivers/block/ll_rw_blk.c

@@ -353,6 +353,8 @@ static void blk_pre_flush_end_io(struct request *flush_rq)
 	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 request *flush_rq)
 	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(request_queue_t *q, struct request *rq)
 	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",
@@ -2456,6 +2459,8 @@ static void __blk_put_request(request_queue_t *q, struct request *req)
 	if (unlikely(--req->ref_count))
 		return;
 
+	elv_completed_request(q, req);
+
 	req->rq_status = RQ_INACTIVE;
 	req->rl = NULL;
 
@@ -2466,8 +2471,6 @@ static void __blk_put_request(request_queue_t *q, struct request *req)
 	if (rl) {
 		int rw = rq_data_dir(req);
 
-		elv_completed_request(q, req);
-
 		BUG_ON(!list_empty(&req->queuelist));
 
 		blk_free_request(q, req);
@@ -2477,14 +2480,14 @@ static void __blk_put_request(request_queue_t *q, struct request *req)
 
 void blk_put_request(struct request *req)
 {
-	/*
-	 * if req->rl isn't set, this request didnt originate from the
-	 * block layer, so it's safe to just disregard it
-	 */
-	if (req->rl) {
 	unsigned long flags;
 	request_queue_t *q = req->q;
 
+	/*
+	 * Gee, IDE calls in w/ NULL q.  Fix IDE and remove the
+	 * following if (q) test.
+	 */
+	if (q) {
 		spin_lock_irqsave(q->queue_lock, flags);
 		__blk_put_request(q, req);
 		spin_unlock_irqrestore(q->queue_lock, flags);

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)
@@ -332,6 +334,13 @@ struct request_queue
 	prepare_flush_fn	*prepare_flush_fn;
 	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
 	 */
@@ -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 *req, int uptodate);
 
 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);
 }
 
 /*

include/linux/elevator.h

@@ -8,18 +8,17 @@ typedef void (elevator_merge_req_fn) (request_queue_t *, struct request *, struc
 
 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 *);