[PATCH 1/3] block: Provide icq in request allocation data

[Jan Kara <jack@xxxxxxx>]

Currently we lookup ICQ only after the request is allocated. However BFQ
will want to decide how many scheduler tags it allows a given bfq queue
(effectively a process) to consume based on cgroup weight. So lookup ICQ
earlier and provide it in struct blk_mq_alloc_data so that BFQ can use
it.

Signed-off-by: Jan Kara <jack@xxxxxxx>
---
 block/blk-mq-sched.c | 18 ++++++++++--------
 block/blk-mq-sched.h |  3 ++-
 block/blk-mq.c       |  7 ++++---
 block/blk-mq.h       |  1 +
 4 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index c838d81ac058..3e34f5bb24ae 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -18,9 +18,8 @@
 #include "blk-mq-tag.h"
 #include "blk-wbt.h"
 
-void blk_mq_sched_assign_ioc(struct request *rq)
+struct io_cq *blk_mq_sched_lookup_icq(struct request_queue *q)
 {
-	struct request_queue *q = rq->q;
 	struct io_context *ioc;
 	struct io_cq *icq;
 
@@ -29,17 +28,20 @@ void blk_mq_sched_assign_ioc(struct request *rq)
 	 */
 	ioc = current->io_context;
 	if (!ioc)
-		return;
+		return NULL;
 
 	spin_lock_irq(&q->queue_lock);
 	icq = ioc_lookup_icq(ioc, q);
 	spin_unlock_irq(&q->queue_lock);
+	if (icq)
+		return icq;
+	return ioc_create_icq(ioc, q, GFP_ATOMIC);
+}
 
-	if (!icq) {
-		icq = ioc_create_icq(ioc, q, GFP_ATOMIC);
-		if (!icq)
-			return;
-	}
+void blk_mq_sched_assign_ioc(struct request *rq, struct io_cq *icq)
+{
+	if (!icq)
+		return;
 	get_io_context(icq->ioc);
 	rq->elv.icq = icq;
 }
diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h
index 5246ae040704..4529991e55e6 100644
--- a/block/blk-mq-sched.h
+++ b/block/blk-mq-sched.h
@@ -7,7 +7,8 @@
 
 #define MAX_SCHED_RQ (16 * BLKDEV_MAX_RQ)
 
-void blk_mq_sched_assign_ioc(struct request *rq);
+struct io_cq *blk_mq_sched_lookup_icq(struct request_queue *q);
+void blk_mq_sched_assign_ioc(struct request *rq, struct io_cq *icq);
 
 bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
 		unsigned int nr_segs, struct request **merged_request);
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 2c4ac51e54eb..b9d83644158f 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -333,9 +333,7 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
 
 		rq->elv.icq = NULL;
 		if (e && e->type->ops.prepare_request) {
-			if (e->type->icq_cache)
-				blk_mq_sched_assign_ioc(rq);
-
+			blk_mq_sched_assign_ioc(rq, data->icq);
 			e->type->ops.prepare_request(rq);
 			rq->rq_flags |= RQF_ELVPRIV;
 		}
@@ -360,6 +358,9 @@ static struct request *__blk_mq_alloc_request(struct blk_mq_alloc_data *data)
 		data->flags |= BLK_MQ_REQ_NOWAIT;
 
 	if (e) {
+		if (!op_is_flush(data->cmd_flags) && e->type->icq_cache &&
+		    e->type->ops.prepare_request)
+			data->icq = blk_mq_sched_lookup_icq(q);
 		/*
 		 * Flush/passthrough requests are special and go directly to the
 		 * dispatch list. Don't include reserved tags in the
diff --git a/block/blk-mq.h b/block/blk-mq.h
index d08779f77a26..c502232384c6 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -151,6 +151,7 @@ static inline struct blk_mq_ctx *blk_mq_get_ctx(struct request_queue *q)
 struct blk_mq_alloc_data {
 	/* input parameter */
 	struct request_queue *q;
+	struct io_cq *icq;
 	blk_mq_req_flags_t flags;
 	unsigned int shallow_depth;
 	unsigned int cmd_flags;
-- 
2.26.2