[PATCH] 04/05 remove last_merge handling from ioscheds

Remove last_merge handling from all ioscheds.  This patch
removes merging capability of noop iosched.

Signed-off-by: Tejun Heo <htejun@gmail.com>

4 files changed, 8 insertions, 114 deletions

diff --git a/drivers/block/as-iosched.c b/drivers/block/as-iosched.c
index 1775ffe9edc7..5d20e4bcbc78 100644
--- a/drivers/block/as-iosched.c
+++ b/drivers/block/as-iosched.c
@@ -279,14 +279,6 @@ static inline void as_del_arq_hash(struct as_rq *arq)
                 __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(struct as_data *ad, sector_t offset)
                 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(request_queue_t *q, struct request *rq)
                 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 *ad, struct as_rq *arq, struct as_rq *alia
         /*
          * 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_t *q, struct request *rq)
                 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 request **req, struct bio *bio)
         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 request **req, struct bio *bio)
 
         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_queue_t *q, struct request *req)
                  * behind the disk head. We currently don't bother adjusting.
                  */
         }
-
-        if (arq->on_hash)
-                q->last_merge = req;
 }
 
 static void
diff --git a/drivers/block/cfq-iosched.c b/drivers/block/cfq-iosched.c
index 7b14160e0798..62a19ed0443b 100644
--- a/drivers/block/cfq-iosched.c
+++ b/drivers/block/cfq-iosched.c
@@ -304,14 +304,6 @@ static inline void cfq_del_crq_hash(struct cfq_rq *crq)
         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 request *rq)
 
         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 request **req, struct bio *bio)
         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 request **req, struct bio *bio)
 
         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_queue_t *q, struct request *req)
                 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_queue_t *q, struct request *rq)
 
         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);
 }
 
diff --git a/drivers/block/deadline-iosched.c b/drivers/block/deadline-iosched.c
index 07de4d24ddba..43d93155efb8 100644
--- a/drivers/block/deadline-iosched.c
+++ b/drivers/block/deadline-iosched.c
@@ -112,15 +112,6 @@ static inline void deadline_del_drq_hash(struct deadline_rq *drq)
                 __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_queue *q, struct request *rq)
         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(request_queue_t *q, struct request *rq)
         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, struct request **req, struct bio *bio)
         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, struct request **req, struct bio *bio)
 
         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(request_queue_t *q, struct request *req)
                 deadline_del_drq_rb(dd, drq);
                 deadline_add_drq_rb(dd, drq);
         }
-
-        q->last_merge = req;
 }
 
 static void
diff --git a/drivers/block/noop-iosched.c b/drivers/block/noop-iosched.c
index bc2252b6f2e5..f56b8edb06e4 100644
--- a/drivers/block/noop-iosched.c
+++ b/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_add_tail(q, rq);
-
-        /*
-         * 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(request_queue_t *q, int force)
 
 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,
         },