tcm_fc: Generate TASK_SET_FULL status for DataIN failures

This patch changes ft_queue_data_in() to set SAM_STAT_TASK_SET_FULL
status upon a lport->tt.seq_send() failure, where it will now stop
sending subsequent DataIN, and immediately attempt to send the
response with exception status.

Sending a response with SAM_STAT_TASK_SET_FULL status is useful in
order to signal the initiator that it should try to reduce it's
current queue_depth, to lower the number of outstanding I/Os on
the wire.

Also, add a check to skip sending DataIN if TASK_SET_FULL status
has already been set due to a response lport->tt.seq_send()
failure, that has asked target-core to requeue a response.

Reported-by: Vasu Dev <vasu.dev@linux.intel.com>
Reviewed-by: Vasu Dev <vasu.dev@linux.intel.com>
Cc: Jun Wu <jwu@stormojo.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 15 insertions, 2 deletions

diff --git a/drivers/target/tcm_fc/tfc_io.c b/drivers/target/tcm_fc/tfc_io.c
index e415af32115a..97b486c3dda1 100644
--- a/drivers/target/tcm_fc/tfc_io.c
+++ b/drivers/target/tcm_fc/tfc_io.c
@@ -82,6 +82,10 @@ int ft_queue_data_in(struct se_cmd *se_cmd)
 
         if (cmd->aborted)
                 return 0;
+
+        if (se_cmd->scsi_status == SAM_STAT_TASK_SET_FULL)
+                goto queue_status;
+
         ep = fc_seq_exch(cmd->seq);
         lport = ep->lp;
         cmd->seq = lport->tt.seq_start_next(cmd->seq);
@@ -178,14 +182,23 @@ int ft_queue_data_in(struct se_cmd *se_cmd)
                                FC_TYPE_FCP, f_ctl, fh_off);
                 error = lport->tt.seq_send(lport, seq, fp);
                 if (error) {
-                        /* XXX For now, initiator will retry */
-                        pr_err_ratelimited("%s: Failed to send frame %p, "
+                        pr_info_ratelimited("%s: Failed to send frame %p, "
                                                 "xid <0x%x>, remaining %zu, "
                                                 "lso_max <0x%x>\n",
                                                 __func__, fp, ep->xid,
                                                 remaining, lport->lso_max);
+                        /*
+                         * Go ahead and set TASK_SET_FULL status ignoring the
+                         * rest of the DataIN, and immediately attempt to
+                         * send the response via ft_queue_status() in order
+                         * to notify the initiator that it should reduce it's
+                         * per LUN queue_depth.
+                         */
+                        se_cmd->scsi_status = SAM_STAT_TASK_SET_FULL;
+                        break;
                 }
         }
+queue_status:
         return ft_queue_status(se_cmd);
 }