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

[Meneghini, John]

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