From a9ed27a764156929efe714033edb3e9023c5f321 Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Wed, 18 Aug 2021 09:09:25 +0800 Subject: [PATCH] blk-mq: fix is_flush_rq is_flush_rq() is called from bt_iter()/bt_tags_iter(), and runs the following check: hctx->fq->flush_rq == req but the passed hctx from bt_iter()/bt_tags_iter() may be NULL because: 1) memory re-order in blk_mq_rq_ctx_init(): rq->mq_hctx = data->hctx; ... refcount_set(&rq->ref, 1); OR 2) tag re-use and ->rqs[] isn't updated with new request. Fix the issue by re-writing is_flush_rq() as: return rq->end_io == flush_end_io; which turns out simpler to follow and immune to data race since we have ordered WRITE rq->end_io and refcount_set(&rq->ref, 1). Fixes: 2e315dc07df0 ("blk-mq: grab rq->refcount before calling ->fn in blk_mq_tagset_busy_iter") Cc: "Blank-Burian, Markus, Dr." Cc: Yufen Yu Signed-off-by: Ming Lei Link: https://lore.kernel.org/r/20210818010925.607383-1-ming.lei@redhat.com Signed-off-by: Jens Axboe --- block/blk-flush.c | 5 +++++ block/blk-mq.c | 2 +- block/blk.h | 6 +----- 3 files changed, 7 insertions(+), 6 deletions(-) diff --git a/block/blk-flush.c b/block/blk-flush.c index 4912c8dbb1d8a..4201728bf3a5a 100644 --- a/block/blk-flush.c +++ b/block/blk-flush.c @@ -262,6 +262,11 @@ static void flush_end_io(struct request *flush_rq, blk_status_t error) spin_unlock_irqrestore(&fq->mq_flush_lock, flags); } +bool is_flush_rq(struct request *rq) +{ + return rq->end_io == flush_end_io; +} + /** * blk_kick_flush - consider issuing flush request * @q: request_queue being kicked diff --git a/block/blk-mq.c b/block/blk-mq.c index 914c71ecc72a4..9d4fdc2be88a5 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -911,7 +911,7 @@ static bool blk_mq_req_expired(struct request *rq, unsigned long *next) void blk_mq_put_rq_ref(struct request *rq) { - if (is_flush_rq(rq, rq->mq_hctx)) + if (is_flush_rq(rq)) rq->end_io(rq, 0); else if (refcount_dec_and_test(&rq->ref)) __blk_mq_free_request(rq); diff --git a/block/blk.h b/block/blk.h index 4b885c0f6708d..cb01429c162c6 100644 --- a/block/blk.h +++ b/block/blk.h @@ -44,11 +44,7 @@ static inline void __blk_get_queue(struct request_queue *q) kobject_get(&q->kobj); } -static inline bool -is_flush_rq(struct request *req, struct blk_mq_hw_ctx *hctx) -{ - return hctx->fq->flush_rq == req; -} +bool is_flush_rq(struct request *req); struct blk_flush_queue *blk_alloc_flush_queue(int node, int cmd_size, gfp_t flags); -- 2.39.5