Re: [PATCH v3] nvme-tcp: Do not reset transport on data digest errors

Sagi Grimberg
2021-08-30T11:25:44Z

On 8/26/21 1:21 AM, Daniel Wagner wrote:
> The spec says
>
> 7.4.6.1 Digest Error handling
>
> When a host detects a data digest error in a C2HData PDU, that host
> shall continue processing C2HData PDUs associated with the command and
> when the command processing has completed, if a successful status was
> returned by the controller, the host shall fail the command with a
> non-fatal transport error.
>
> Currently the transport is reseted when a data digest error is
> detected. Instead, when a digest error is detected, mark the final
> status as NVME_SC_DATA_XFER_ERROR and let the upper layer handle
> the error.
>
> In order to keep track of the final result maintain a status field in
> nvme_tcp_request object and use it to overwrite the completion queue
> status (which might be successful even though a digest error has been
> detected) when completing the request.
>
> Reviewed-by: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Daniel Wagner <dwagner@suse.de>
> ---
> The status member placed so that it fills up a hole in struct
> nvme_tcp_request:
>
> struct nvme_tcp_request {
> struct nvme_request req; /* 0 32 */
> void * pdu; /* 32 8 */
> struct nvme_tcp_queue * queue; /* 40 8 */
> u32 data_len; /* 48 4 */
> u32 pdu_len; /* 52 4 */
> u32 pdu_sent; /* 56 4 */
> u16 ttag; /* 60 2 */
> u16 status; /* 62 2 */
> /* --- cacheline 1 boundary (64 bytes) --- */
> struct list_head entry; /* 64 16 */
> struct llist_node lentry; /* 80 8 */
> __le32 ddgst; /* 88 4 */
>
> /* XXX 4 bytes hole, try to pack */
>
> struct bio * curr_bio; /* 96 8 */
> struct iov_iter iter; /* 104 40 */
> /* --- cacheline 2 boundary (128 bytes) was 16 bytes ago --- */
> size_t offset; /* 144 8 */
> size_t data_sent; /* 152 8 */
> enum nvme_tcp_send_state state; /* 160 4 */
>
> /* size: 168, cachelines: 3, members: 16 */
> /* sum members: 160, holes: 1, sum holes: 4 */
> /* padding: 4 */
> /* last cacheline: 40 bytes */
> };
>
> v3:
> - initialize req->status in nvme_tcp_setup_cmd_pdu()
> - add rb tag from Hannes
>
> v2:
> - https://lore.kernel.org/linux-nvme/20210825124259.28707-1-dwagner@suse.de/
> - moved 'status' from nvme_tcp_queue to nvme_tcp_request.
>
> v1:
> - https://lore.kernel.org/linux-nvme/20210805121541.77613-1-dwagner@suse.de/
>
> drivers/nvme/host/tcp.c | 23 +++++++++++++++++++----
> 1 file changed, 19 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
> index 645025620154..29ef0f74f620 100644
> --- a/drivers/nvme/host/tcp.c
> +++ b/drivers/nvme/host/tcp.c
> @@ -45,6 +45,7 @@ struct nvme_tcp_request {
> u32 pdu_len;
> u32 pdu_sent;
> u16 ttag;
> + u16 status;
> struct list_head entry;
> struct llist_node lentry;
> __le32 ddgst;
> @@ -485,7 +486,9 @@ static void nvme_tcp_error_recovery(struct nvme_ctrl *ctrl)
> static int nvme_tcp_process_nvme_cqe(struct nvme_tcp_queue *queue,
> struct nvme_completion *cqe)
> {
> + struct nvme_tcp_request *req;
> struct request *rq;
> + u16 status;
>
> rq = nvme_find_rq(nvme_tcp_tagset(queue), cqe->command_id);
> if (!rq) {
> @@ -496,7 +499,12 @@ static int nvme_tcp_process_nvme_cqe(struct nvme_tcp_queue *queue,
> return -EINVAL;
> }
>
> - if (!nvme_try_complete_req(rq, cqe->status, cqe->result))
> + req = blk_mq_rq_to_pdu(rq);
> + status = req->status;
> + if (status == NVME_SC_SUCCESS)
> + status = cqe->status;

Maybe more intuitive to skip the local status variable?
/* */
if (req->status == NVME_SC_SUCCESS)
req->status = cqe->status;

This way it is always consistent completing with req->status.