tcm_fc: Handle DDP/SW fc_frame_payload_get failures in ft_recv_write_data

Problem: HW DDP context was not invalidated in case of ABORTS, etc...
This leads to the problem where memory pages which are used for DDP
as user descriptor could get reused for some other purpose (such as to
satisfy new memory allocation request either by kernel or user mode threads)
and since HW DDP context was not invalidated, HW continue to write to
those pages, hence causing memory corruption.

Fix: Either on incoming ABORTS or due to exchange time out, allowed the
target to cleanup HW DDP context if it was setup for respective ft_cmd.
Added new function to perform this cleanup, furthur it can be enhanced
for other cleanup activity.  Fix ft_recv_write_data() to properly handle
fc_frame_payload_get to return pointer to payload if it exist. If there is
no payload which is most common case (+ve case in case if DDP is working
as expected, it will return NULL. Yes, scope of buf is limited to printk.
Invalidation of HW context (which is done inside ft_invl_hw_context() is
necessary in SUCCESS and FAILURE case of DDP. Hence invalidation is DONE
as long as there was DDP setup (whether it worked correctly or not,

NOTE: For some reason, if there is any error w.r.t DDP such as out of
order packet reception, HW simply post the full packet in rx queue.
Signed-off-by: Kiran Patil <kiran.patil@intel.com>
Cc: Robert W Love <robert.w.love@intel.com>
Signed-off-by: Nicholas A. Bellinger <nab@linux-iscsi.org>

drivers/target/tcm_fc/tcm_fc.h

@@ -187,4 +187,9 @@ void ft_dump_cmd(struct ft_cmd *, const char *caller);
 
 ssize_t ft_format_wwn(char *, size_t, u64);
 
+/*
+ * Underlying HW specific helper function
+ */
+void ft_invl_hw_context(struct ft_cmd *);
+
 #endif /* __TCM_FC_H__ */

drivers/target/tcm_fc/tfc_cmd.c

@@ -320,6 +320,7 @@ static void ft_recv_seq(struct fc_seq *sp, struct fc_frame *fp, void *arg)
 	default:
 		pr_debug("%s: unhandled frame r_ctl %x\n",
 		       __func__, fh->fh_r_ctl);
+		ft_invl_hw_context(cmd);
 		fc_frame_free(fp);
 		transport_generic_free_cmd(&cmd->se_cmd, 0, 0);
 		break;

drivers/target/tcm_fc/tfc_io.c

@@ -214,62 +214,49 @@ void ft_recv_write_data(struct ft_cmd *cmd, struct fc_frame *fp)
 	if (!(ntoh24(fh->fh_f_ctl) & FC_FC_REL_OFF))
 		goto drop;
 
+	f_ctl = ntoh24(fh->fh_f_ctl);
+	ep = fc_seq_exch(seq);
+	lport = ep->lp;
+	if (cmd->was_ddp_setup) {
+		BUG_ON(!ep);
+		BUG_ON(!lport);
+	}
+
 	/*
-	 * Doesn't expect even single byte of payload. Payload
+	 * Doesn't expect payload if DDP is setup. Payload
 	 * is expected to be copied directly to user buffers
-	 * due to DDP (Large Rx offload) feature, hence
-	 * BUG_ON if BUF is non-NULL
+	 * due to DDP (Large Rx offload),
 	 */
 	buf = fc_frame_payload_get(fp, 1);
-	if (cmd->was_ddp_setup && buf) {
-		pr_debug("%s: When DDP was setup, not expected to"
-				 "receive frame with payload, Payload shall be"
-				 "copied directly to buffer instead of coming "
-				 "via. legacy receive queues\n", __func__);
-		BUG_ON(buf);
-	}
+	if (buf)
+		pr_err("%s: xid 0x%x, f_ctl 0x%x, cmd->sg %p, "
+				"cmd->sg_cnt 0x%x. DDP was setup"
+				" hence not expected to receive frame with "
+				"payload, Frame will be dropped if "
+				"'Sequence Initiative' bit in f_ctl is "
+				"not set\n", __func__, ep->xid, f_ctl,
+				cmd->sg, cmd->sg_cnt);
+	/*
+ 	 * Invalidate HW DDP context if it was setup for respective
+ 	 * command. Invalidation of HW DDP context is requited in both
+ 	 * situation (success and error). 
+ 	 */
+	ft_invl_hw_context(cmd);
 
 	/*
-	 * If ft_cmd indicated 'ddp_setup', in that case only the last frame
-	 * should come with 'TSI bit being set'. If 'TSI bit is not set and if
-	 * data frame appears here, means error condition. In both the cases
-	 * release the DDP context (ddp_put) and in error case, as well
-	 * initiate error recovery mechanism.
+	 * If "Sequence Initiative (TSI)" bit set in f_ctl, means last
+	 * write data frame is received successfully where payload is
+	 * posted directly to user buffer and only the last frame's
+	 * header is posted in receive queue.
+	 *
+	 * If "Sequence Initiative (TSI)" bit is not set, means error
+	 * condition w.r.t. DDP, hence drop the packet and let explict
+	 * ABORTS from other end of exchange timer trigger the recovery.
 	 */
-	ep = fc_seq_exch(seq);
-	if (cmd->was_ddp_setup) {
-		BUG_ON(!ep);
-		lport = ep->lp;
-		BUG_ON(!lport);
-	}
-	if (cmd->was_ddp_setup && ep->xid != FC_XID_UNKNOWN) {
-		f_ctl = ntoh24(fh->fh_f_ctl);
-		/*
-		 * If TSI bit set in f_ctl, means last write data frame is
-		 * received successfully where payload is posted directly
-		 * to user buffer and only the last frame's header is posted
-		 * in legacy receive queue
-		 */
-		if (f_ctl & FC_FC_SEQ_INIT) { /* TSI bit set in FC frame */
-			cmd->write_data_len = lport->tt.ddp_done(lport,
-								ep->xid);
-			goto last_frame;
-		} else {
-			/*
-			 * Updating the write_data_len may be meaningless at
-			 * this point, but just in case if required in future
-			 * for debugging or any other purpose
-			 */
-			pr_err("%s: Received frame with TSI bit not"
-					" being SET, dropping the frame, "
-					"cmd->sg <%p>, cmd->sg_cnt <0x%x>\n",
-					__func__, cmd->sg, cmd->sg_cnt);
-			cmd->write_data_len = lport->tt.ddp_done(lport,
-							      ep->xid);
-			lport->tt.seq_exch_abort(cmd->seq, 0);
-			goto drop;
-		}
-	}
+	if (f_ctl & FC_FC_SEQ_INIT)
+		goto last_frame;
+	else
+		goto drop;
 
 	rel_off = ntohl(fh->fh_parm_offset);
 	frame_len = fr_len(fp);
@@ -332,3 +319,39 @@ void ft_recv_write_data(struct ft_cmd *cmd, struct fc_frame *fp)
 drop:
 	fc_frame_free(fp);
 }
+
+/*
+ * Handle and cleanup any HW specific resources if
+ * received ABORTS, errors, timeouts.
+ */
+void ft_invl_hw_context(struct ft_cmd *cmd)
+{
+	struct fc_seq *seq = cmd->seq;
+	struct fc_exch *ep = NULL;
+	struct fc_lport *lport = NULL;
+
+	BUG_ON(!cmd);
+
+	/* Cleanup the DDP context in HW if DDP was setup */
+	if (cmd->was_ddp_setup && seq) {
+		ep = fc_seq_exch(seq);
+		if (ep) {
+			lport = ep->lp;
+			if (lport && (ep->xid <= lport->lro_xid))
+				/*
+				 * "ddp_done" trigger invalidation of HW
+				 * specific DDP context
+				 */
+				cmd->write_data_len = lport->tt.ddp_done(lport,
+								      ep->xid);
+
+				/*
+				 * Resetting same variable to indicate HW's
+				 * DDP context has been invalidated to avoid
+				 * re_invalidation of same context (context is
+				 * identified using ep->xid)
+				 */
+				cmd->was_ddp_setup = 0;
+		}
+	}
+}