dm-mpath need this API for improving IO scheduling. The IO schedule is actually done on dm-rq(mpath) queue, instead of underlying devices. If we set q->nr_requests as q->queue_depth on underlying devices, we can get the queue's busy feedback by simply checking if blk_get_request() returns successfully. This way will make block layer's I/O schedule more effective on dm-rq device. Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> --- block/blk-core.c | 4 +++- block/blk-sysfs.c | 5 +---- block/blk.h | 2 -- include/linux/blkdev.h | 1 + 4 files changed, 5 insertions(+), 7 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index aebe676225e6..9752aac9821c 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -1108,7 +1108,8 @@ int blk_update_nr_requests(struct request_queue *q, unsigned int nr) struct request_list *rl; int on_thresh, off_thresh; - WARN_ON_ONCE(q->mq_ops); + if (q->mq_ops) + return blk_mq_update_nr_requests(q, nr); spin_lock_irq(q->queue_lock); q->nr_requests = nr; @@ -1145,6 +1146,7 @@ int blk_update_nr_requests(struct request_queue *q, unsigned int nr) spin_unlock_irq(q->queue_lock); return 0; } +EXPORT_SYMBOL(blk_update_nr_requests); /** * __get_request - get a free request diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index b8362c0df51d..2dbef5dbd195 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -77,10 +77,7 @@ queue_requests_store(struct request_queue *q, const char *page, size_t count) if (nr < BLKDEV_MIN_RQ) nr = BLKDEV_MIN_RQ; - if (q->request_fn) - err = blk_update_nr_requests(q, nr); - else - err = blk_mq_update_nr_requests(q, nr); + err = blk_update_nr_requests(q, nr); if (err) return err; diff --git a/block/blk.h b/block/blk.h index fa4f232afc18..5bf662da2417 100644 --- a/block/blk.h +++ b/block/blk.h @@ -308,8 +308,6 @@ static inline int queue_congestion_off_threshold(struct request_queue *q) return q->nr_congestion_off; } -extern int blk_update_nr_requests(struct request_queue *, unsigned int); - /* * Contribute to IO statistics IFF: * diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 460294bb0fa5..226b97142999 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -1229,6 +1229,7 @@ struct request_queue *blk_alloc_queue(gfp_t); struct request_queue *blk_alloc_queue_node(gfp_t, int); extern void blk_put_queue(struct request_queue *); extern void blk_set_queue_dying(struct request_queue *); +extern int blk_update_nr_requests(struct request_queue *, unsigned int); /* * block layer runtime pm functions -- 2.9.5
