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 <redacted>
---
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/ (local)
  - moved 'status' from nvme_tcp_queue to nvme_tcp_request.

v1:
  - https://lore.kernel.org/linux-nvme/20210805121541.77613-1-dwagner@suse.de/ (local)

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;