bfq: update internal depth state when queue depth changes

A previous commit moved the shallow depth and BFQ depth map calculations
to be done at init time, moving it outside of the hotter IO path. This
potentially causes hangs if the users changes the depth of the scheduler
map, by writing to the 'nr_requests' sysfs file for that device.

Add a blk-mq-sched hook that allows blk-mq to inform the scheduler if
the depth changes, so that the scheduler can update its internal state.

Tested-by: Kai Krakow <kai@kaishome.de>
Reported-by: Paolo Valente <paolo.valente@linaro.org>
Fixes: f0635b8a416e ("bfq: calculate shallow depths at init time")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index dfb8cb0af13a872737e07647de307e9e44017f0d..5ba1e0d841b4d552e3858ad30888e489669772bd 100644 (file)
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -5396,7 +5396,7 @@ static unsigned int bfq_update_depths(struct bfq_data *bfqd,
        return min_shallow;
 }
 
-static int bfq_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int index)
+static void bfq_depth_updated(struct blk_mq_hw_ctx *hctx)
 {
        struct bfq_data *bfqd = hctx->queue->elevator->elevator_data;
        struct blk_mq_tags *tags = hctx->sched_tags;
@@ -5404,6 +5404,11 @@ static int bfq_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int index)
 
        min_shallow = bfq_update_depths(bfqd, &tags->bitmap_tags);
        sbitmap_queue_min_shallow_depth(&tags->bitmap_tags, min_shallow);
+}
+
+static int bfq_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int index)
+{
+       bfq_depth_updated(hctx);
        return 0;
 }
 
@@ -5826,6 +5831,7 @@ static struct elevator_type iosched_bfq_mq = {
                .requests_merged        = bfq_requests_merged,
                .request_merged         = bfq_request_merged,
                .has_work               = bfq_has_work,
+               .depth_updated          = bfq_depth_updated,
                .init_hctx              = bfq_init_hctx,
                .init_sched             = bfq_init_queue,
                .exit_sched             = bfq_exit_queue,

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 9516304a38ee37c70f897185e6bfe94fc7fe79f8..fc60ed7e940ead5ae7d7332ee9f64b9ffe922aca 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3135,6 +3135,8 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
                }
                if (ret)
                        break;
+               if (q->elevator && q->elevator->type->ops.depth_updated)
+                       q->elevator->type->ops.depth_updated(hctx);
        }
 
        if (!ret)

diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index 2e9e2763bf47dbea239976034e32fd11f14826f7..6e8bc53740f050f63883ea6b7d077e5911bdca9f 100644 (file)
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -31,6 +31,7 @@ struct elevator_mq_ops {
        void (*exit_sched)(struct elevator_queue *);
        int (*init_hctx)(struct blk_mq_hw_ctx *, unsigned int);
        void (*exit_hctx)(struct blk_mq_hw_ctx *, unsigned int);
+       void (*depth_updated)(struct blk_mq_hw_ctx *);
 
        bool (*allow_merge)(struct request_queue *, struct request *, struct bio *);
        bool (*bio_merge)(struct blk_mq_hw_ctx *, struct bio *);