From 6cfeadbff3f8905f2854735ebb88e581402c16c4 Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Thu, 16 Jun 2022 09:44:01 +0800 Subject: [PATCH] blk-mq: don't clear flush_rq from tags->rqs[] commit 364b61818f65 ("blk-mq: clearing flush request reference in tags->rqs[]") is added to clear the to-be-free flush request from tags->rqs[] for avoiding use-after-free on the flush rq. Yu Kuai reported that blk_mq_clear_flush_rq_mapping() slows down boot time by ~8s because running scsi probe which may create and remove lots of unpresent LUNs on megaraid-sas which uses BLK_MQ_F_TAG_HCTX_SHARED and each request queue has lots of hw queues. Improve the situation by not running blk_mq_clear_flush_rq_mapping if disk isn't added when there can't be any flush request issued. Reviewed-by: Christoph Hellwig Reported-by: Yu Kuai Signed-off-by: Ming Lei Link: https://lore.kernel.org/r/20220616014401.817001-4-ming.lei@redhat.com Signed-off-by: Jens Axboe --- block/blk-mq.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 4cdb08a709122b..33145ba52c9606 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -3431,8 +3431,9 @@ static void blk_mq_exit_hctx(struct request_queue *q, if (blk_mq_hw_queue_mapped(hctx)) blk_mq_tag_idle(hctx); - blk_mq_clear_flush_rq_mapping(set->tags[hctx_idx], - set->queue_depth, flush_rq); + if (blk_queue_init_done(q)) + blk_mq_clear_flush_rq_mapping(set->tags[hctx_idx], + set->queue_depth, flush_rq); if (set->ops->exit_request) set->ops->exit_request(set, flush_rq, hctx_idx);