Re: nvme: Return BLK_STS_TARGET if the DNR bit is set

From: Hannes Reinecke <hare@suse.de>
To: Mike Snitzer <snitzer@redhat.com>, Christoph Hellwig <hch@lst.de>,
	Jens Axboe <axboe@kernel.dk>
Cc: dm-devel@redhat.com, linux-block@vger.kernel.org,
	linux-nvme@lists.infradead.org
Subject: Re: nvme: Return BLK_STS_TARGET if the DNR bit is set
Date: Fri, 16 Apr 2021 07:58:10 +0200	[thread overview]
Message-ID: <c715a982-4a75-d30f-e6f6-15ad125e7b89@suse.de> (raw)
In-Reply-To: <20210415231126.8746-1-snitzer@redhat.com>

On 4/16/21 1:11 AM, Mike Snitzer wrote:
> BZ: 1948690
> Upstream Status: RHEL-only
> 
> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
> 
> rhel-8.git commit ef4ab90c12db5e0e50800ec323736b95be7a6ff5
> Author: Mike Snitzer <snitzer@redhat.com>
> Date:   Tue Aug 25 21:52:45 2020 -0400
> 
>     [nvme] nvme: Return BLK_STS_TARGET if the DNR bit is set
>     
>     Message-id: <20200825215248.2291-8-snitzer@redhat.com>
>     Patchwork-id: 325178
>     Patchwork-instance: patchwork
>     O-Subject: [RHEL8.3 PATCH 07/10] nvme: Return BLK_STS_TARGET if the DNR bit is set
>     Bugzilla: 1843515
>     RH-Acked-by: David Milburn <dmilburn@redhat.com>
>     RH-Acked-by: Gopal Tiwari <gtiwari@redhat.com>
>     RH-Acked-by: Ewan Milne <emilne@redhat.com>
>     
>     BZ: 1843515
>     Upstream Status: RHEL-only
>     
>     If the DNR bit is set we should not retry the command, even if
>     the standard status evaluation indicates so.
>     
>     SUSE is carrying this patch in their kernel:
>     https://lwn.net/Articles/800370/
>     
>     Based on patch posted for upstream inclusion but rejected:
>     v1: https://lore.kernel.org/linux-nvme/20190806111036.113233-1-hare@suse.de/
>     v2: https://lore.kernel.org/linux-nvme/20190807071208.101882-1-hare@suse.de/
>     v2-keith: https://lore.kernel.org/linux-nvme/20190807144725.GB25621@localhost.localdomain/
>     v3: https://lore.kernel.org/linux-nvme/20190812075147.79598-1-hare@suse.de/
>     v3-keith: https://lore.kernel.org/linux-nvme/20190813141510.GB32686@localhost.localdomain/
>     
>     This commit's change is basically "v3-keith".
>     
>     Signed-off-by: Mike Snitzer <snitzer@redhat.com>
>     Signed-off-by: Frantisek Hrbata <fhrbata@redhat.com>
> 
> ---
>  drivers/nvme/host/core.c |    3 +++
>  1 file changed, 3 insertions(+)
> 
> Index: linux-rhel9/drivers/nvme/host/core.c
> ===================================================================
> --- linux-rhel9.orig/drivers/nvme/host/core.c
> +++ linux-rhel9/drivers/nvme/host/core.c
> @@ -237,6 +237,9 @@ static void nvme_delete_ctrl_sync(struct
>  
>  static blk_status_t nvme_error_status(u16 status)
>  {
> +	if (unlikely(status & NVME_SC_DNR))
> +		return BLK_STS_TARGET;
> +
>  	switch (status & 0x7ff) {
>  	case NVME_SC_SUCCESS:
>  		return BLK_STS_OK;
> 
No; this is most likely wrong for quite some machines.
At this time we don't have a fixed mapping for the DNR bit;
some BLK_STS_XX codes can be retried, some might, others should not; we
never went so far as to formally code that.

But mapping it to BLK_STS_TARGET is not the correct way here.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
hare@suse.de			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)