block: optionally merge discontiguous discard bios into a single request

[mirror_ubuntu-artful-kernel.git] / block / blk-merge.c

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 182398cb152490d96b7e48c4fd74f11657c8e665..2afa262425d102e5c1500912f3b6d77525754566 100644 (file)
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -482,13 +482,6 @@ int blk_rq_map_sg(struct request_queue *q, struct request *rq,
 }
 EXPORT_SYMBOL(blk_rq_map_sg);
 
-static void req_set_nomerge(struct request_queue *q, struct request *req)
-{
-       req->cmd_flags |= REQ_NOMERGE;
-       if (req == q->last_merge)
-               q->last_merge = NULL;
-}
-
 static inline int ll_new_hw_segment(struct request_queue *q,
                                    struct request *req,
                                    struct bio *bio)
@@ -659,31 +652,32 @@ static void blk_account_io_merge(struct request *req)
 }
 
 /*
- * Has to be called with the request spinlock acquired
+ * For non-mq, this has to be called with the request spinlock acquired.
+ * For mq with scheduling, the appropriate queue wide lock should be held.
  */
-static int attempt_merge(struct request_queue *q, struct request *req,
-                         struct request *next)
+static struct request *attempt_merge(struct request_queue *q,
+                                    struct request *req, struct request *next)
 {
        if (!rq_mergeable(req) || !rq_mergeable(next))
-               return 0;
+               return NULL;
 
        if (req_op(req) != req_op(next))
-               return 0;
+               return NULL;
 
        /*
         * not contiguous
         */
        if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
-               return 0;
+               return NULL;
 
        if (rq_data_dir(req) != rq_data_dir(next)
            || req->rq_disk != next->rq_disk
            || req_no_special_merge(next))
-               return 0;
+               return NULL;
 
        if (req_op(req) == REQ_OP_WRITE_SAME &&
            !blk_write_same_mergeable(req->bio, next->bio))
-               return 0;
+               return NULL;
 
        /*
         * If we are allowed to merge, then append bio list
@@ -692,7 +686,7 @@ static int attempt_merge(struct request_queue *q, struct request *req,
         * counts here.
         */
        if (!ll_merge_requests_fn(q, req, next))
-               return 0;
+               return NULL;
 
        /*
         * If failfast settings disagree or any of the two is already
@@ -732,42 +726,51 @@ static int attempt_merge(struct request_queue *q, struct request *req,
        if (blk_rq_cpu_valid(next))
                req->cpu = next->cpu;
 
-       /* owner-ship of bio passed from next to req */
+       /*
+        * ownership of bio passed from next to req, return 'next' for
+        * the caller to free
+        */
        next->bio = NULL;
-       __blk_put_request(q, next);
-       return 1;
+       return next;
 }
 
-int attempt_back_merge(struct request_queue *q, struct request *rq)
+struct request *attempt_back_merge(struct request_queue *q, struct request *rq)
 {
        struct request *next = elv_latter_request(q, rq);
 
        if (next)
                return attempt_merge(q, rq, next);
 
-       return 0;
+       return NULL;
 }
 
-int attempt_front_merge(struct request_queue *q, struct request *rq)
+struct request *attempt_front_merge(struct request_queue *q, struct request *rq)
 {
        struct request *prev = elv_former_request(q, rq);
 
        if (prev)
                return attempt_merge(q, prev, rq);
 
-       return 0;
+       return NULL;
 }
 
 int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
                          struct request *next)
 {
        struct elevator_queue *e = q->elevator;
+       struct request *free;
 
-       if (e->type->ops.elevator_allow_rq_merge_fn)
-               if (!e->type->ops.elevator_allow_rq_merge_fn(q, rq, next))
+       if (!e->uses_mq && e->type->ops.sq.elevator_allow_rq_merge_fn)
+               if (!e->type->ops.sq.elevator_allow_rq_merge_fn(q, rq, next))
                        return 0;
 
-       return attempt_merge(q, rq, next);
+       free = attempt_merge(q, rq, next);
+       if (free) {
+               __blk_put_request(q, free);
+               return 1;
+       }
+
+       return 0;
 }
 
 bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
@@ -798,9 +801,12 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
        return true;
 }
 
-int blk_try_merge(struct request *rq, struct bio *bio)
+enum elv_merge blk_try_merge(struct request *rq, struct bio *bio)
 {
-       if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
+       if (req_op(rq) == REQ_OP_DISCARD &&
+           queue_max_discard_segments(rq->q) > 1)
+               return ELEVATOR_DISCARD_MERGE;
+       else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
                return ELEVATOR_BACK_MERGE;
        else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
                return ELEVATOR_FRONT_MERGE;