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From: Jens Axboe <axboe@kernel.dk>
To: "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>
Subject: [PATCH] block: don't dereference request after flush insertion
Date: Sat, 16 Oct 2021 19:35:39 -0600	[thread overview]
Message-ID: <f2f17f46-ff3a-01c4-bfd4-8dec836ec343@kernel.dk> (raw)

We could have a race here, where the request gets freed before we call
into blk_mq_run_hw_queue(). If this happens, we cannot rely on the state
of the request.

Grab the hardware context before inserting the flush.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

---

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 2197cfbf081f..22b30a89bf3a 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2468,9 +2468,10 @@ void blk_mq_submit_bio(struct bio *bio)
 	}
 
 	if (unlikely(is_flush_fua)) {
+		struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
 		/* Bypass scheduler for flush requests */
 		blk_insert_flush(rq);
-		blk_mq_run_hw_queue(rq->mq_hctx, true);
+		blk_mq_run_hw_queue(hctx, true);
 	} else if (plug && (q->nr_hw_queues == 1 ||
 		   blk_mq_is_shared_tags(rq->mq_hctx->flags) ||
 		   q->mq_ops->commit_rqs || !blk_queue_nonrot(q))) {
-- 
Jens Axboe


             reply	other threads:[~2021-10-17  1:35 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-17  1:35 Jens Axboe [this message]
2021-10-18  1:49 ` [PATCH] block: don't dereference request after flush insertion Ming Lei
2021-10-18  1:50   ` Jens Axboe
2021-10-18  2:02     ` Ming Lei
2021-10-18  2:10       ` Jens Axboe
2021-10-18  8:34         ` Christoph Hellwig
2021-10-18  2:11       ` Ming Lei
2021-10-18  2:16         ` Jens Axboe
2021-10-18  2:30           ` Ming Lei
2021-10-18  2:42 ` Ming Lei
2021-10-18  2:44   ` Jens Axboe

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