[SCSI] iscsi: Some fixes in preparation for bidirectional support - exp_datasn

This patch fixes handling of expected datasn/r2tsn as received from
target. It is done according to: T10 rfc3720 section 3.2.2.3. Data Sequencing.

. unify expected datasn/r2tsn into one counter
. calculate than check expected datasn/r2tsn. On error print a message
  and fail the request. (TODO use iscsi retransmits)
. remove the FIXME   ;)
. avoid zero length memset

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

3 files changed, 15 insertions, 10 deletions

diff --git a/drivers/scsi/iscsi_tcp.c b/drivers/scsi/iscsi_tcp.c
index 8201e6c4d8a9..17fc79c408a2 100644
--- a/drivers/scsi/iscsi_tcp.c
+++ b/drivers/scsi/iscsi_tcp.c
@@ -229,10 +229,13 @@ iscsi_data_rsp(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
         if (tcp_conn->in.datalen == 0)
                 return 0;
 
-        if (ctask->datasn != datasn)
+        if (tcp_ctask->exp_datasn != datasn) {
+                debug_tcp("%s: ctask->exp_datasn(%d) != rhdr->datasn(%d)\n",
+                          __FUNCTION__, tcp_ctask->exp_datasn, datasn);
                 return ISCSI_ERR_DATASN;
+        }
 
-        ctask->datasn++;
+        tcp_ctask->exp_datasn++;
 
         tcp_ctask->data_offset = be32_to_cpu(rhdr->offset);
         if (tcp_ctask->data_offset + tcp_conn->in.datalen > ctask->total_length)
@@ -365,15 +368,16 @@ iscsi_r2t_rsp(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
                 return ISCSI_ERR_DATALEN;
         }
 
-        if (tcp_ctask->exp_r2tsn && tcp_ctask->exp_r2tsn != r2tsn)
+        if (tcp_ctask->exp_datasn != r2tsn){
+                debug_tcp("%s: ctask->exp_datasn(%d) != rhdr->r2tsn(%d)\n",
+                          __FUNCTION__, tcp_ctask->exp_datasn, r2tsn);
                 return ISCSI_ERR_R2TSN;
+        }
 
         rc = iscsi_check_assign_cmdsn(session, (struct iscsi_nopin*)rhdr);
         if (rc)
                 return rc;
 
-        /* FIXME: use R2TSN to detect missing R2T */
-
         /* fill-in new R2T associated with the task */
         spin_lock(&session->lock);
         if (!ctask->sc || ctask->mtask ||
@@ -414,7 +418,7 @@ iscsi_r2t_rsp(struct iscsi_conn *conn, struct iscsi_cmd_task *ctask)
 
         iscsi_solicit_data_init(conn, ctask, r2t);
 
-        tcp_ctask->exp_r2tsn = r2tsn + 1;
+        tcp_ctask->exp_datasn = r2tsn + 1;
         __kfifo_put(tcp_ctask->r2tqueue, (void*)&r2t, sizeof(void*));
         tcp_ctask->xmstate |= XMSTATE_SOL_HDR;
         list_move_tail(&ctask->running, &conn->xmitqueue);
@@ -1284,10 +1288,10 @@ iscsi_tcp_cmd_init(struct iscsi_cmd_task *ctask)
 
         tcp_ctask->sent = 0;
         tcp_ctask->sg_count = 0;
+        tcp_ctask->exp_datasn = 0;
 
         if (sc->sc_data_direction == DMA_TO_DEVICE) {
                 tcp_ctask->xmstate = XMSTATE_W_HDR;
-                tcp_ctask->exp_r2tsn = 0;
                 BUG_ON(ctask->total_length == 0);
 
                 if (sc->use_sg) {
diff --git a/drivers/scsi/iscsi_tcp.h b/drivers/scsi/iscsi_tcp.h
index 32736831790e..f909edbf61ee 100644
--- a/drivers/scsi/iscsi_tcp.h
+++ b/drivers/scsi/iscsi_tcp.h
@@ -152,7 +152,7 @@ struct iscsi_tcp_cmd_task {
         struct scatterlist      *sg;                    /* per-cmd SG list  */
         struct scatterlist      *bad_sg;                /* assert statement */
         int                     sg_count;               /* SG's to process  */
-        uint32_t                exp_r2tsn;
+        uint32_t                exp_datasn;             /* expected target's R2TSN/DataSN */
         int                     data_offset;
         struct iscsi_r2t_info   *r2t;                   /* in progress R2T    */
         struct iscsi_queue      r2tpool;
diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
index 5e6a42429c39..eb5113607958 100644
--- a/drivers/scsi/libiscsi.c
+++ b/drivers/scsi/libiscsi.c
@@ -120,7 +120,9 @@ static void iscsi_prep_scsi_cmd_pdu(struct iscsi_cmd_task *ctask)
         session->cmdsn++;
         hdr->exp_statsn = cpu_to_be32(conn->exp_statsn);
         memcpy(hdr->cdb, sc->cmnd, sc->cmd_len);
-        memset(&hdr->cdb[sc->cmd_len], 0, MAX_COMMAND_SIZE - sc->cmd_len);
+        if (sc->cmd_len < MAX_COMMAND_SIZE)
+                memset(&hdr->cdb[sc->cmd_len], 0,
+                        MAX_COMMAND_SIZE - sc->cmd_len);
 
         ctask->data_count = 0;
         if (sc->sc_data_direction == DMA_TO_DEVICE) {
@@ -165,7 +167,6 @@ static void iscsi_prep_scsi_cmd_pdu(struct iscsi_cmd_task *ctask)
                         /* No unsolicit Data-Out's */
                         ctask->hdr->flags |= ISCSI_FLAG_CMD_FINAL;
         } else {
-                ctask->datasn = 0;
                 hdr->flags |= ISCSI_FLAG_CMD_FINAL;
                 zero_data(hdr->dlength);