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

[Daniel Wagner]

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@xxxxxxx>
Signed-off-by: Daniel Wagner <dwagner@xxxxxxx>
---
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@xxxxxxx/
 - moved 'status' from nvme_tcp_queue to nvme_tcp_request.

v1:
 - https://lore.kernel.org/linux-nvme/20210805121541.77613-1-dwagner@xxxxxxx/

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;
+
+	if (!nvme_try_complete_req(rq, status, cqe->result))
 		nvme_complete_rq(rq);
 	queue->nr_cqe++;
 
@@ -758,7 +766,7 @@ static int nvme_tcp_recv_data(struct nvme_tcp_queue *queue, struct sk_buff *skb,
 			queue->ddgst_remaining = NVME_TCP_DIGEST_LENGTH;
 		} else {
 			if (pdu->hdr.flags & NVME_TCP_F_DATA_SUCCESS) {
-				nvme_tcp_end_request(rq, NVME_SC_SUCCESS);
+				nvme_tcp_end_request(rq, req->status);
 				queue->nr_cqe++;
 			}
 			nvme_tcp_init_recv_ctx(queue);
@@ -788,18 +796,24 @@ static int nvme_tcp_recv_ddgst(struct nvme_tcp_queue *queue,
 		return 0;
 
 	if (queue->recv_ddgst != queue->exp_ddgst) {
+		struct request *rq = nvme_cid_to_rq(nvme_tcp_tagset(queue),
+					pdu->command_id);
+		struct nvme_tcp_request *req = blk_mq_rq_to_pdu(rq);
+
+		req->status = NVME_SC_DATA_XFER_ERROR;
+
 		dev_err(queue->ctrl->ctrl.device,
 			"data digest error: recv %#x expected %#x\n",
 			le32_to_cpu(queue->recv_ddgst),
 			le32_to_cpu(queue->exp_ddgst));
-		return -EIO;
 	}
 
 	if (pdu->hdr.flags & NVME_TCP_F_DATA_SUCCESS) {
 		struct request *rq = nvme_cid_to_rq(nvme_tcp_tagset(queue),
 					pdu->command_id);
+		struct nvme_tcp_request *req = blk_mq_rq_to_pdu(rq);
 
-		nvme_tcp_end_request(rq, NVME_SC_SUCCESS);
+		nvme_tcp_end_request(rq, req->status);
 		queue->nr_cqe++;
 	}
 
@@ -2293,6 +2307,7 @@ static blk_status_t nvme_tcp_setup_cmd_pdu(struct nvme_ns *ns,
 		return ret;
 
 	req->state = NVME_TCP_SEND_CMD_PDU;
+	req->status = NVME_SC_SUCCESS;
 	req->offset = 0;
 	req->data_sent = 0;
 	req->pdu_len = 0;
-- 
2.29.2