[PATCH] 02/05: update ioscheds to use generic dispatch queue

This patch updates all four ioscheds to use generic dispatch
queue.  There's one behavior change in as-iosched.

* In as-iosched, when force dispatching
  (ELEVATOR_INSERT_BACK), batch_data_dir is reset to REQ_SYNC
  and changed_batch and new_batch are cleared to zero.  This
  prevernts AS from doing incorrect update_write_batch after
  the forced dispatched requests are finished.

* In cfq-iosched, cfqd->rq_in_driver currently counts the
  number of activated (removed) requests to determine
  whether queue-kicking is needed and cfq_max_depth has been
  reached.  With generic dispatch queue, I think counting
  the number of dispatched requests would be more appropriate.

* cfq_max_depth can be lowered to 1 again.

Original from Tejun Heo, modified version applied.

Signed-off-by: Jens Axboe <axboe@suse.de>

1 files changed, 17 insertions, 78 deletions

diff --git a/drivers/block/deadline-iosched.c b/drivers/block/deadline-iosched.c
index 52a3ae5289a0..07de4d24ddba 100644
--- a/drivers/block/deadline-iosched.c
+++ b/drivers/block/deadline-iosched.c
@@ -50,7 +50,6 @@ struct deadline_data {
          * next in sort order. read, write or both are NULL
          */
         struct deadline_rq *next_drq[2];
-        struct list_head *dispatch;     /* driver dispatch queue */
         struct list_head *hash;         /* request hash */
         unsigned int batching;          /* number of sequential requests made */
         sector_t last_sector;           /* head position */
@@ -239,10 +238,9 @@ deadline_del_drq_rb(struct deadline_data *dd, struct deadline_rq *drq)
                         dd->next_drq[data_dir] = rb_entry_drq(rbnext);
         }
 
-        if (ON_RB(&drq->rb_node)) {
-                rb_erase(&drq->rb_node, DRQ_RB_ROOT(dd, drq));
-                RB_CLEAR(&drq->rb_node);
-        }
+        BUG_ON(!ON_RB(&drq->rb_node));
+        rb_erase(&drq->rb_node, DRQ_RB_ROOT(dd, drq));
+        RB_CLEAR(&drq->rb_node);
 }
 
 static struct request *
@@ -286,7 +284,7 @@ deadline_find_first_drq(struct deadline_data *dd, int data_dir)
 /*
  * add drq to rbtree and fifo
  */
-static inline void
+static void
 deadline_add_request(struct request_queue *q, struct request *rq)
 {
         struct deadline_data *dd = q->elevator->elevator_data;
@@ -315,14 +313,11 @@ deadline_add_request(struct request_queue *q, struct request *rq)
 static void deadline_remove_request(request_queue_t *q, struct request *rq)
 {
         struct deadline_rq *drq = RQ_DATA(rq);
+        struct deadline_data *dd = q->elevator->elevator_data;
 
-        if (drq) {
-                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);
-        }
+        list_del_init(&drq->fifo);
+        deadline_remove_merge_hints(q, drq);
+        deadline_del_drq_rb(dd, drq);
 }
 
 static int
@@ -452,7 +447,7 @@ deadline_move_to_dispatch(struct deadline_data *dd, struct deadline_rq *drq)
         request_queue_t *q = drq->request->q;
 
         deadline_remove_request(q, drq->request);
-        list_add_tail(&drq->request->queuelist, dd->dispatch);
+        elv_dispatch_add_tail(q, drq->request);
 }
 
 /*
@@ -502,8 +497,9 @@ static inline int deadline_check_fifo(struct deadline_data *dd, int ddir)
  * deadline_dispatch_requests selects the best request according to
  * read/write expire, fifo_batch, etc
  */
-static int deadline_dispatch_requests(struct deadline_data *dd)
+static int deadline_dispatch_requests(request_queue_t *q, int force)
 {
+        struct deadline_data *dd = q->elevator->elevator_data;
         const int reads = !list_empty(&dd->fifo_list[READ]);
         const int writes = !list_empty(&dd->fifo_list[WRITE]);
         struct deadline_rq *drq;
@@ -597,65 +593,12 @@ dispatch_request:
         return 1;
 }
 
-static struct request *deadline_next_request(request_queue_t *q)
-{
-        struct deadline_data *dd = q->elevator->elevator_data;
-        struct request *rq;
-
-        /*
-         * if there are still requests on the dispatch queue, grab the first one
-         */
-        if (!list_empty(dd->dispatch)) {
-dispatch:
-                rq = list_entry_rq(dd->dispatch->next);
-                return rq;
-        }
-
-        if (deadline_dispatch_requests(dd))
-                goto dispatch;
-
-        return NULL;
-}
-
-static void
-deadline_insert_request(request_queue_t *q, struct request *rq, int where)
-{
-        struct deadline_data *dd = q->elevator->elevator_data;
-
-        /* barriers must flush the reorder queue */
-        if (unlikely(rq->flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER)
-                        && where == ELEVATOR_INSERT_SORT))
-                where = ELEVATOR_INSERT_BACK;
-
-        switch (where) {
-                case ELEVATOR_INSERT_BACK:
-                        while (deadline_dispatch_requests(dd))
-                                ;
-                        list_add_tail(&rq->queuelist, dd->dispatch);
-                        break;
-                case ELEVATOR_INSERT_FRONT:
-                        list_add(&rq->queuelist, dd->dispatch);
-                        break;
-                case ELEVATOR_INSERT_SORT:
-                        BUG_ON(!blk_fs_request(rq));
-                        deadline_add_request(q, rq);
-                        break;
-                default:
-                        printk("%s: bad insert point %d\n", __FUNCTION__,where);
-                        return;
-        }
-}
-
 static int deadline_queue_empty(request_queue_t *q)
 {
         struct deadline_data *dd = q->elevator->elevator_data;
 
-        if (!list_empty(&dd->fifo_list[WRITE])
-            || !list_empty(&dd->fifo_list[READ])
-            || !list_empty(dd->dispatch))
-                return 0;
-
-        return 1;
+        return list_empty(&dd->fifo_list[WRITE])
+                && list_empty(&dd->fifo_list[READ]);
 }
 
 static struct request *
@@ -733,7 +676,6 @@ static int deadline_init_queue(request_queue_t *q, elevator_t *e)
         INIT_LIST_HEAD(&dd->fifo_list[WRITE]);
         dd->sort_list[READ] = RB_ROOT;
         dd->sort_list[WRITE] = RB_ROOT;
-        dd->dispatch = &q->queue_head;
         dd->fifo_expire[READ] = read_expire;
         dd->fifo_expire[WRITE] = write_expire;
         dd->writes_starved = writes_starved;
@@ -748,10 +690,8 @@ static void deadline_put_request(request_queue_t *q, struct request *rq)
         struct deadline_data *dd = q->elevator->elevator_data;
         struct deadline_rq *drq = RQ_DATA(rq);
 
-        if (drq) {
-                mempool_free(drq, dd->drq_pool);
-                rq->elevator_private = NULL;
-        }
+        mempool_free(drq, dd->drq_pool);
+        rq->elevator_private = NULL;
 }
 
 static int
@@ -917,9 +857,8 @@ static struct elevator_type iosched_deadline = {
                 .elevator_merge_fn =            deadline_merge,
                 .elevator_merged_fn =           deadline_merged_request,
                 .elevator_merge_req_fn =        deadline_merged_requests,
-                .elevator_next_req_fn =         deadline_next_request,
-                .elevator_add_req_fn =          deadline_insert_request,
-                .elevator_remove_req_fn =       deadline_remove_request,
+                .elevator_dispatch_fn =         deadline_dispatch_requests,
+                .elevator_add_req_fn =          deadline_add_request,
                 .elevator_queue_empty_fn =      deadline_queue_empty,
                 .elevator_former_req_fn =       deadline_former_request,
                 .elevator_latter_req_fn =       deadline_latter_request,