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From:   Daniel Wagner <dwagner@suse.de>
To:     linux-nvme@lists.infradead.org
Cc:     linux-kernel@vger.kernel.org, Hannes Reinecke <hare@suse.de>,
        Keith Busch <kbusch@kernel.org>, Jens Axboe <axboe@fb.com>,
        Christoph Hellwig <hch@lst.de>, Daniel Wagner <dwagner@suse.de>
Subject: [PATCH] nvme-multipath: Reset bi_disk to ns head when failover
Date:   Mon,  3 May 2021 14:57:41 +0200
Message-Id: <20210503125741.68117-1-dwagner@suse.de>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

The path can be stale when we failover. If we don't reset the bdev to
the ns head and the I/O finally completes in end_io() it will triggers
a crash. By resetting the to ns head disk so that the submit path can
map the request to an active path.

Signed-off-by: Daniel Wagner <dwagner@suse.de>
---

The patch is against nvme-5.13.

[ 6552.155244] Call Trace:
[ 6552.155251]  bio_endio+0x74/0x120
[ 6552.155260]  nvme_ns_head_submit_bio+0x36f/0x3e0 [nvme_core]
[ 6552.155266]  ? __switch_to_asm+0x34/0x70
[ 6552.155269]  ? __switch_to_asm+0x40/0x70
[ 6552.155271]  submit_bio_noacct+0x175/0x490
[ 6552.155274]  ? __switch_to_asm+0x34/0x70
[ 6552.155277]  ? __switch_to_asm+0x34/0x70
[ 6552.155284]  ? nvme_requeue_work+0x5a/0x70 [nvme_core]
[ 6552.155290]  nvme_requeue_work+0x5a/0x70 [nvme_core]
[ 6552.155296]  process_one_work+0x1f4/0x3e0
[ 6552.155299]  worker_thread+0x2d/0x3e0
[ 6552.155302]  ? process_one_work+0x3e0/0x3e0
[ 6552.155305]  kthread+0x10d/0x130
[ 6552.155307]  ? kthread_park+0xa0/0xa0
[ 6552.155311]  ret_from_fork+0x35/0x40

 drivers/nvme/host/multipath.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 0d0de3433f37..0faf267faa58 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -69,7 +69,9 @@ void nvme_failover_req(struct request *req)
 {
 	struct nvme_ns *ns = req->q->queuedata;
 	u16 status = nvme_req(req)->status & 0x7ff;
+	struct block_device *bdev;
 	unsigned long flags;
+	struct bio *bio;
 
 	nvme_mpath_clear_current_path(ns);
 
@@ -83,9 +85,13 @@ void nvme_failover_req(struct request *req)
 		queue_work(nvme_wq, &ns->ctrl->ana_work);
 	}
 
+	bdev = bdget_disk(ns->head->disk, 0);
 	spin_lock_irqsave(&ns->head->requeue_lock, flags);
+	for (bio = req->bio; bio; bio = bio->bi_next)
+		bio_set_dev(bio, bdev);
 	blk_steal_bios(&ns->head->requeue_list, req);
 	spin_unlock_irqrestore(&ns->head->requeue_lock, flags);
+	bdput(bdev);
 
 	blk_mq_end_request(req, 0);
 	kblockd_schedule_work(&ns->head->requeue_work);
-- 
2.29.2