[RESEND PATCH] nvme: explicitly use normal NVMe error handling when appropriate

[Mike Snitzer]

Maybe because I didn't cc linux-block?
Only way that I know to "upload this patch there" is to have cc'd
linux-block.

But the patch is in dm-devel's patchwork here:
https://patchwork.kernel.org/patch/11712563/

Is that sufficient for your needs?

Thanks,
Mike

On Thu, Aug 13 2020 at 11:29am -0400,
Meneghini, John <John.Meneghini at netapp.com> wrote:

> Mike, 
> 
> I don't see your patch at:
> 
> https://patchwork.kernel.org/project/linux-block/list/?submitter=1643
> 
> Can you please upload this patch there?
> 
> Thanks,
> 
> /John
> 
> On 8/13/20, 10:48 AM, "Mike Snitzer" <snitzer at redhat.com> wrote:
> 
>     Commit 764e9332098c0 ("nvme-multipath: do not reset on unknown
>     status"), among other things, fixed NVME_SC_CMD_INTERRUPTED error
>     handling by changing multipathing's nvme_failover_req() to short-circuit
>     path failover and then fallback to NVMe's normal error handling (which
>     takes care of NVME_SC_CMD_INTERRUPTED).
> 
>     This detour through native NVMe multipathing code is unwelcome because
>     it prevents NVMe core from handling NVME_SC_CMD_INTERRUPTED independent
>     of any multipathing concerns.
> 
>     Introduce nvme_status_needs_local_error_handling() to prioritize
>     non-failover retry, when appropriate, in terms of normal NVMe error
>     handling.  nvme_status_needs_local_error_handling() will naturely evolve
>     to include handling of any other errors that normal error handling must
>     be used for.
> 
>     nvme_failover_req()'s ability to fallback to normal NVMe error handling
>     has been preserved because it may be useful for future NVME_SC that
>     nvme_status_needs_local_error_handling() hasn't been trained for yet.
> 
>     Signed-off-by: Mike Snitzer <snitzer at redhat.com>
>     ---
>      drivers/nvme/host/core.c | 16 ++++++++++++++--
>      1 file changed, 14 insertions(+), 2 deletions(-)
> 
>     diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
>     index 88cff309d8e4..be749b690af7 100644
>     --- a/drivers/nvme/host/core.c
>     +++ b/drivers/nvme/host/core.c
>     @@ -252,6 +252,16 @@ static inline bool nvme_req_needs_retry(struct request *req)
>             return true;
>      }
> 
>     +static inline bool nvme_status_needs_local_error_handling(u16 status)
>     +{
>     +       switch (status & 0x7ff) {
>     +       case NVME_SC_CMD_INTERRUPTED:
>     +               return true;
>     +       default:
>     +               return false;
>     +       }
>     +}
>     +
>      static void nvme_retry_req(struct request *req)
>      {
>             struct nvme_ns *ns = req->q->queuedata;
>     @@ -270,7 +280,8 @@ static void nvme_retry_req(struct request *req)
> 
>      void nvme_complete_rq(struct request *req)
>      {
>     -       blk_status_t status = nvme_error_status(nvme_req(req)->status);
>     +       u16 nvme_status = nvme_req(req)->status;
>     +       blk_status_t status = nvme_error_status(nvme_status);
> 
>             trace_nvme_complete_rq(req);
> 
>     @@ -280,7 +291,8 @@ void nvme_complete_rq(struct request *req)
>                     nvme_req(req)->ctrl->comp_seen = true;
> 
>             if (unlikely(status != BLK_STS_OK && nvme_req_needs_retry(req))) {
>     -               if ((req->cmd_flags & REQ_NVME_MPATH) && nvme_failover_req(req))
>     +               if (!nvme_status_needs_local_error_handling(nvme_status) &&
>     +                   (req->cmd_flags & REQ_NVME_MPATH) && nvme_failover_req(req))
>                             return;
> 
>                     if (!blk_queue_dying(req->q)) {
>     --
>     2.18.0
> 
>