block: Provide blk_mq_sched_get_icq()

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 provide a
function blk_mq_sched_get_icq() so that BFQ can lookup ICQ earlier.

Acked-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20211125133645.27483-1-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index b942b38..98c6a97 100644 (file)
--- 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_get_icq(struct request_queue *q)
 {
-       struct request_queue *q = rq->q;
        struct io_context *ioc;
        struct io_cq *icq;
 
@@ -28,22 +27,27 @@ void blk_mq_sched_assign_ioc(struct request *rq)
        if (unlikely(!current->io_context))
                create_task_io_context(current, GFP_ATOMIC, q->node);
 
-       /*
-        * May not have an IO context if it's a passthrough request
-        */
+       /* May not have an IO context if context creation failed */
        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);
+}
+EXPORT_SYMBOL(blk_mq_sched_get_icq);
 
-       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;
+
+       icq = blk_mq_sched_get_icq(rq->q);
+       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 25d1034..add651e 100644 (file)
--- a/block/blk-mq-sched.h
+++ b/block/blk-mq-sched.h
@@ -8,6 +8,7 @@
 
 #define MAX_SCHED_RQ (16 * BLKDEV_DEFAULT_RQ)
 
+struct io_cq *blk_mq_sched_get_icq(struct request_queue *q);
 void blk_mq_sched_assign_ioc(struct request *rq);
 
 bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,