[PATCH] nvme-multipath: Reset bi_disk to ns head when failover

[PATCH] nvme-multipath: Reset bi_disk to ns head when failover

[Daniel Wagner]

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

Re: [PATCH] nvme-multipath: Reset bi_disk to ns head when failover

[Hannes Reinecke]

On 5/3/21 2:57 PM, Daniel Wagner wrote:
> 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);
> 
Maybe a WARN_ON(!bdev) after bdget_disk(), but otherwise:

Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

Re: [PATCH] nvme-multipath: Reset bi_disk to ns head when failover

[Christoph Hellwig]

On Mon, May 03, 2021 at 02:57:41PM +0200, Daniel Wagner wrote:
> 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.

There is no bi_disk in nvme-5.13, but fortunately that slipped in only
in the subject.

> +	bdev = bdget_disk(ns->head->disk, 0);

Please just use ns->head->disk->part0 directly.  No need for the
reference and bdget_disk is about to go away.

Re: [PATCH] nvme-multipath: Reset bi_disk to ns head when failover

[kernel test robot]

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Hi Daniel,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linux/master]
[also build test ERROR on hch-configfs/for-next linus/master v5.12 next-20210503]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Daniel-Wagner/nvme-multipath-Reset-bi_disk-to-ns-head-when-failover/20210503-210018
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 1fe5501ba1abf2b7e78295df73675423bd6899a0
config: x86_64-randconfig-a006-20210503 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build):
        # https://github.com/0day-ci/linux/commit/603164e7d6800851ee5366bfaff31084453284bb
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Daniel-Wagner/nvme-multipath-Reset-bi_disk-to-ns-head-when-failover/20210503-210018
        git checkout 603164e7d6800851ee5366bfaff31084453284bb
        # save the attached .config to linux build tree
        make W=1 W=1 ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>, old ones prefixed by <<):

>> ERROR: modpost: "bdget_disk" [drivers/nvme/host/nvme-core.ko] undefined!

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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