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From: Christoph Hellwig <hch@lst.de>
To: Jens Axboe <axboe@kernel.dk>
Cc: Tejun Heo <tj@kernel.org>,
	linux-block@vger.kernel.org, Ming Lei <ming.lei@redhat.com>
Subject: [PATCH 2/4] block: split bio_queue_enter from blk_queue_enter
Date: Mon, 20 Sep 2021 13:24:03 +0200	[thread overview]
Message-ID: <20210920112405.1299667-3-hch@lst.de> (raw)
In-Reply-To: <20210920112405.1299667-1-hch@lst.de>

To prepare for fixing a gendisk shutdown race, open code the
blk_queue_enter logic in bio_queue_enter.  This also remove the
pointless flags translation.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-core.c | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 4c078681f39b8..be7cd1819b605 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -475,18 +475,32 @@ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags)
 static inline int bio_queue_enter(struct bio *bio)
 {
 	struct request_queue *q = bio->bi_bdev->bd_disk->queue;
-	bool nowait = bio->bi_opf & REQ_NOWAIT;
-	int ret;
 
-	ret = blk_queue_enter(q, nowait ? BLK_MQ_REQ_NOWAIT : 0);
-	if (unlikely(ret)) {
-		if (nowait && !blk_queue_dying(q))
+	while (!blk_try_enter_queue(q, false)) {
+		if (bio->bi_opf & REQ_NOWAIT) {
 			bio_wouldblock_error(bio);
-		else
+			return -EBUSY;
+		}
+
+		/*
+		 * read pair of barrier in blk_freeze_queue_start(), we need to
+		 * order reading __PERCPU_REF_DEAD flag of .q_usage_counter and
+		 * reading .mq_freeze_depth or queue dying flag, otherwise the
+		 * following wait may never return if the two reads are
+		 * reordered.
+		 */
+		smp_rmb();
+		wait_event(q->mq_freeze_wq,
+			   (!q->mq_freeze_depth &&
+			    blk_pm_resume_queue(false, q)) ||
+			   blk_queue_dying(q));
+		if (blk_queue_dying(q)) {
 			bio_io_error(bio);
+			return -ENODEV;
+		}
 	}
 
-	return ret;
+	return 0;
 }
 
 void blk_queue_exit(struct request_queue *q)
-- 
2.30.2


  parent reply	other threads:[~2021-09-20 11:26 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-20 11:24 tear down file system I/O in del_gendisk Christoph Hellwig
2021-09-20 11:24 ` [PATCH 1/4] block: factor out a blk_try_enter_queue helper Christoph Hellwig
2021-09-21  3:17   ` Bart Van Assche
2021-09-20 11:24 ` Christoph Hellwig [this message]
2021-09-21  3:25   ` [PATCH 2/4] block: split bio_queue_enter from blk_queue_enter Bart Van Assche
2021-09-20 11:24 ` [PATCH 3/4] block: drain file system I/O on del_gendisk Christoph Hellwig
2021-09-20 11:24 ` [PATCH 4/4] block: keep q_usage_counter in atomic mode after del_gendisk Christoph Hellwig
2021-09-21  3:29   ` Bart Van Assche
2021-09-21  9:07     ` Christoph Hellwig
2021-09-21  3:38 ` tear down file system I/O in del_gendisk Bart Van Assche
2021-09-21  9:08   ` Christoph Hellwig
2021-09-21 14:24     ` Bart Van Assche
2021-09-21 22:33       ` Bart Van Assche
2021-09-22 17:22 tear down file system I/O in del_gendisk v2 Christoph Hellwig
2021-09-22 17:22 ` [PATCH 2/4] block: split bio_queue_enter from blk_queue_enter Christoph Hellwig

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