tcm_fc: Generate TASK_SET_FULL status for response failures

This patch changes ft_queue_status() to set SAM_STAT_TASK_SET_FULL
status upon lport->tt.seq_send( failure, and return -EAGAIN to notify
target-core to attempt to requeue the response.

It also does the same for a fc_frame_alloc() failures, 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.

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, 16 insertions, 3 deletions

diff --git a/drivers/target/tcm_fc/tfc_cmd.c b/drivers/target/tcm_fc/tfc_cmd.c
index f5fd515b2bee..be0c0d08c56a 100644
--- a/drivers/target/tcm_fc/tfc_cmd.c
+++ b/drivers/target/tcm_fc/tfc_cmd.c
@@ -128,6 +128,7 @@ int ft_queue_status(struct se_cmd *se_cmd)
         struct fc_lport *lport;
         struct fc_exch *ep;
         size_t len;
+        int rc;
 
         if (cmd->aborted)
                 return 0;
@@ -137,9 +138,10 @@ int ft_queue_status(struct se_cmd *se_cmd)
         len = sizeof(*fcp) + se_cmd->scsi_sense_length;
         fp = fc_frame_alloc(lport, len);
         if (!fp) {
-                /* XXX shouldn't just drop it - requeue and retry? */
-                return 0;
+                se_cmd->scsi_status = SAM_STAT_TASK_SET_FULL;
+                return -ENOMEM;
         }
+
         fcp = fc_frame_payload_get(fp, len);
         memset(fcp, 0, len);
         fcp->resp.fr_status = se_cmd->scsi_status;
@@ -170,7 +172,18 @@ int ft_queue_status(struct se_cmd *se_cmd)
         fc_fill_fc_hdr(fp, FC_RCTL_DD_CMD_STATUS, ep->did, ep->sid, FC_TYPE_FCP,
                        FC_FC_EX_CTX | FC_FC_LAST_SEQ | FC_FC_END_SEQ, 0);
 
-        lport->tt.seq_send(lport, cmd->seq, fp);
+        rc = lport->tt.seq_send(lport, cmd->seq, fp);
+        if (rc) {
+                pr_info_ratelimited("%s: Failed to send response frame %p, "
+                                    "xid <0x%x>\n", __func__, fp, ep->xid);
+                /*
+                 * Generate a TASK_SET_FULL status to notify the initiator
+                 * to reduce it's queue_depth after the se_cmd response has
+                 * been re-queued by target-core.
+                 */
+                se_cmd->scsi_status = SAM_STAT_TASK_SET_FULL;
+                return -ENOMEM;
+        }
         lport->tt.exch_done(cmd->seq);
         return 0;
 }