From: Yu Kuai <yukuai3@xxxxxxxxxx> Allocate and free sched_tags while queue is freezed can deadlock[1], this is a long term problem, hence allocate memory before freezing queue and free memory after queue is unfreezed. [1] https://lore.kernel.org/all/0659ea8d-a463-47c8-9180-43c719e106eb@xxxxxxxxxxxxx/ Fixes: e3a2b3f931f5 ("blk-mq: allow changing of queue depth through sysfs") Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx> --- block/blk-mq.c | 22 ++++++++++------------ block/blk-mq.h | 5 ++++- block/blk-sysfs.c | 25 +++++++++++++++++-------- 3 files changed, 31 insertions(+), 21 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 82fa81036115..d85afbb9f031 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -4917,11 +4917,13 @@ void blk_mq_free_tag_set(struct blk_mq_tag_set *set) } EXPORT_SYMBOL(blk_mq_free_tag_set); -int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr) +struct elevator_tags *blk_mq_update_nr_requests(struct request_queue *q, + struct elevator_tags *et, + unsigned int nr) { struct blk_mq_tag_set *set = q->tag_set; + struct elevator_tags *old_et = NULL; struct blk_mq_hw_ctx *hctx; - int ret = 0; unsigned long i; blk_mq_quiesce_queue(q); @@ -4946,23 +4948,19 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr) nr - hctx->sched_tags->nr_reserved_tags); } } else { - queue_for_each_hw_ctx(q, hctx, i) { - if (!hctx->sched_tags) - continue; - blk_mq_tag_update_depth(hctx, &hctx->sched_tags, nr); - if (ret) - goto out; - } + queue_for_each_hw_ctx(q, hctx, i) + hctx->sched_tags = et->tags[i]; + + old_et = q->elevator->et; + q->elevator->et = et; } q->nr_requests = nr; if (q->elevator && q->elevator->type->ops.depth_updated) q->elevator->type->ops.depth_updated(q); -out: blk_mq_unquiesce_queue(q); - - return ret; + return old_et; } /* diff --git a/block/blk-mq.h b/block/blk-mq.h index 731f4578d9a8..6c9d03625ba1 100644 --- a/block/blk-mq.h +++ b/block/blk-mq.h @@ -6,6 +6,7 @@ #include "blk-stat.h" struct blk_mq_tag_set; +struct elevator_tags; struct blk_mq_ctxs { struct kobject kobj; @@ -45,7 +46,9 @@ void blk_mq_submit_bio(struct bio *bio); int blk_mq_poll(struct request_queue *q, blk_qc_t cookie, struct io_comp_batch *iob, unsigned int flags); void blk_mq_exit_queue(struct request_queue *q); -int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr); +struct elevator_tags *blk_mq_update_nr_requests(struct request_queue *q, + struct elevator_tags *tags, + unsigned int nr); void blk_mq_wake_waiters(struct request_queue *q); bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *, bool); diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index 7ea15bf68b4b..a0a7ebad378f 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -64,11 +64,12 @@ static ssize_t queue_requests_show(struct gendisk *disk, char *page) static ssize_t queue_requests_store(struct gendisk *disk, const char *page, size_t count) { - unsigned long nr; - int ret, err; - unsigned int memflags; struct request_queue *q = disk->queue; struct blk_mq_tag_set *set = q->tag_set; + struct elevator_tags *et = NULL; + unsigned int memflags; + unsigned long nr; + int ret; ret = queue_var_store(&nr, page, count); if (ret < 0) @@ -90,16 +91,24 @@ queue_requests_store(struct gendisk *disk, const char *page, size_t count) goto unlock; } + if (q->elevator && nr > q->elevator->et->nr_requests) { + /* allocate memory before freezing queue to prevent deadlock */ + et = blk_mq_alloc_sched_tags(set, q->nr_hw_queues, nr); + if (!et) { + ret = -ENOMEM; + goto unlock; + } + } + memflags = blk_mq_freeze_queue(q); mutex_lock(&q->elevator_lock); - - err = blk_mq_update_nr_requests(disk->queue, nr); - if (err) - ret = err; - + et = blk_mq_update_nr_requests(q, et, nr); mutex_unlock(&q->elevator_lock); blk_mq_unfreeze_queue(q, memflags); + if (et) + blk_mq_free_sched_tags(et, set); + unlock: up_write(&set->update_nr_hwq_lock); return ret; -- 2.39.2
