linux-kernel - [PATCH v2] nvme-multipath: Reset bdev to ns head when failover

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Date:   Mon,  3 May 2021 19:03:03 +0200
From:   Daniel Wagner <dwagner@...e.de>
To:     linux-nvme@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, Hannes Reinecke <hare@...e.de>,
        Keith Busch <kbusch@...nel.org>, Jens Axboe <axboe@...com>,
        Christoph Hellwig <hch@....de>, Daniel Wagner <dwagner@...e.de>
Subject: [PATCH v2] nvme-multipath: Reset bdev to ns head when failover

When a request finally completes in end_io() after it has failed over,
the bdev pointer can be stale and thus the system can crash. Set the
bdev back to ns head, so the request is map to an active path when
resubmitted.

Signed-off-by: Daniel Wagner <dwagner@...e.de>
Reviewed-by: Hannes Reinecke <hare@...e.de>
---
v2:
 - commit header fix s/bi_disk/bdev/
 - new commit message (hopefully it's better English this time.)
 - dropped bdget_disk, use >disk->part0 directly as
   suggested by hch

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 | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 0d0de3433f37..0551796517e6 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -70,6 +70,7 @@ void nvme_failover_req(struct request *req)
 	struct nvme_ns *ns = req->q->queuedata;
 	u16 status = nvme_req(req)->status & 0x7ff;
 	unsigned long flags;
+	struct bio *bio;
 
 	nvme_mpath_clear_current_path(ns);
 
@@ -84,6 +85,8 @@ void nvme_failover_req(struct request *req)
 	}
 
 	spin_lock_irqsave(&ns->head->requeue_lock, flags);
+	for (bio = req->bio; bio; bio = bio->bi_next)
+		bio_set_dev(bio, ns->head->disk->part0);
 	blk_steal_bios(&ns->head->requeue_list, req);
 	spin_unlock_irqrestore(&ns->head->requeue_lock, flags);
 
-- 
2.29.2