[PATCH v2 3/5] blk-mq-sched: make completed_request() callback more useful

[Omar Sandoval]

From: Omar Sandoval <osan...@fb.com>

Currently, this callback is called right after put_request() and has no
distinguishable purpose. Instead, let's call it before put_request() as
soon as I/O has completed on the request, before we account it in
blk-stat. With this, Kyber can enable stats when it sees a latency
outlier and make sure the outlier gets accounted.

Signed-off-by: Omar Sandoval <osan...@fb.com>
---
 block/blk-mq-sched.h     | 11 +++--------
 block/blk-mq.c           |  5 ++++-
 include/linux/elevator.h |  2 +-
 3 files changed, 8 insertions(+), 10 deletions(-)

diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h
index c6e760df0fb4..d846e07bb564 100644
--- a/block/blk-mq-sched.h
+++ b/block/blk-mq-sched.h
@@ -82,17 +82,12 @@ blk_mq_sched_allow_merge(struct request_queue *q, struct 
request *rq,
        return true;
 }
 
-static inline void
-blk_mq_sched_completed_request(struct blk_mq_hw_ctx *hctx, struct request *rq)
+static inline void blk_mq_sched_completed_request(struct request *rq)
 {
-       struct elevator_queue *e = hctx->queue->elevator;
+       struct elevator_queue *e = rq->q->elevator;
 
        if (e && e->type->ops.mq.completed_request)
-               e->type->ops.mq.completed_request(hctx, rq);
-
-       BUG_ON(rq->internal_tag == -1);
-
-       blk_mq_put_tag(hctx, hctx->sched_tags, rq->mq_ctx, rq->internal_tag);
+               e->type->ops.mq.completed_request(rq);
 }
 
 static inline void blk_mq_sched_started_request(struct request *rq)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index b49fdfde7e06..3dbfed6d0e5b 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -350,7 +350,7 @@ void __blk_mq_finish_request(struct blk_mq_hw_ctx *hctx, 
struct blk_mq_ctx *ctx,
        if (rq->tag != -1)
                blk_mq_put_tag(hctx, hctx->tags, ctx, rq->tag);
        if (sched_tag != -1)
-               blk_mq_sched_completed_request(hctx, rq);
+               blk_mq_put_tag(hctx, hctx->sched_tags, ctx, sched_tag);
        blk_mq_sched_restart_queues(hctx);
        blk_queue_exit(q);
 }
@@ -443,6 +443,9 @@ static void __blk_mq_complete_request(struct request *rq)
 {
        struct request_queue *q = rq->q;
 
+       if (rq->internal_tag != -1)
+               blk_mq_sched_completed_request(rq);
+
        blk_mq_stat_add(rq);
 
        if (!q->softirq_done_fn)
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index b7ec315ee7e7..3a216318ae73 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -106,7 +106,7 @@ struct elevator_mq_ops {
        void (*insert_requests)(struct blk_mq_hw_ctx *, struct list_head *, 
bool);
        struct request *(*dispatch_request)(struct blk_mq_hw_ctx *);
        bool (*has_work)(struct blk_mq_hw_ctx *);
-       void (*completed_request)(struct blk_mq_hw_ctx *, struct request *);
+       void (*completed_request)(struct request *);
        void (*started_request)(struct request *);
        void (*requeue_request)(struct request *);
        struct request *(*former_request)(struct request_queue *, struct 
request *);
-- 
2.12.2