Re: [PATCH V2] nvme: Add support for ACRE Command Interrupted status

["Meneghini, John" <John.Meneghini@netapp.com>]

This is an update to say that I've tested this patch and it works as expected. 

When the controller returns a Command Interrupted status the request is avoids nvme_failover_req()
and goes down the nvme_retry_req() path where the CRD is implemented and the command is 
retried after a delay.

If the controllers returns Command Interrupted too many times, and nvme_req(req)->retries
runs down, this results in a device resource error returned to the block layer.  But I think we'll
have this problem with any error.  

[Tue Dec  3 08:18:33 2019] print_req_error: device resource error, dev nvme0c0n1, sector 4610048
[Tue Dec  3 08:18:33 2019] print_req_error: device resource error, dev nvme0c0n1, sector 7112704

The alternative is to stop incrementing nvme_req(req)->retries in nvme_retry_req() when CRD is set.

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 24dc9ed1a11b..ec9794698a20 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -258,8 +258,8 @@ static void nvme_retry_req(struct request *req)
        crd = (nvme_req(req)->status & NVME_SC_CRD) >> 11;
        if (ns && crd)
                delay = ns->ctrl->crdt[crd - 1] * 100;
-
-       nvme_req(req)->retries++;
+       else
+               nvme_req(req)->retries++;
        blk_mq_requeue_request(req, false);
        blk_mq_delay_kick_requeue_list(req->q, delay);
 }

Thoughts?

/John

On 11/27/19, 2:12 PM, "Meneghini, John" <John.Meneghini@netapp.com> wrote:

    From: John Meneghini <johnm@netapp.com>

     - Fixes bug in nvme_complete_rq logic introduced by
       Enhanced Command Retry code. According to TP-4033
       when ACRE is enabled the host needs to support
       the Command Interrupted status.
     - The current code interprets Command Interrupted status
       as a BLK_STS_IOERR. This results in a controller reset
       when REQ_NVME_MPATH is set; in nvme_failover_req.
    
    Fixes: 49cd84b6f8b677e ("nvme: implement Enhanced Command Retry")
    Signed-off-by: John Meneghini <johnm@netapp.com>
    Signed-off-by: Hannes Reinecke <hare@suse.de>
    ---
     drivers/nvme/host/core.c  | 2 ++
     include/linux/blk_types.h | 1 +
     2 files changed, 3 insertions(+)
    
    diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
    index 9696404a6182..24dc9ed1a11b 100644
    --- a/drivers/nvme/host/core.c
    +++ b/drivers/nvme/host/core.c
    @@ -230,6 +230,8 @@ static blk_status_t nvme_error_status(u16 status)
                    return BLK_STS_NEXUS;
            case NVME_SC_HOST_PATH_ERROR:
                    return BLK_STS_TRANSPORT;
    +       case NVME_SC_CMD_INTERRUPTED:
    +               return BLK_STS_DEV_RESOURCE;
            default:
                    return BLK_STS_IOERR;
            }
    diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
    index d688b96d1d63..6efee8f1b91b 100644
    --- a/include/linux/blk_types.h
    +++ b/include/linux/blk_types.h
    @@ -84,6 +84,7 @@ static inline bool blk_path_error(blk_status_t error)
            case BLK_STS_NEXUS:
            case BLK_STS_MEDIUM:
            case BLK_STS_PROTECTION:
    +       case BLK_STS_DEV_RESOURCE:
                    return false;
            }
     
    -- 
    2.21.0