staging: lustre: return +ve for blocked lnet message

returned value of lnet_post_send_locked and
lnet_post_routed_recv_locked are changed to -ve by:
http://review.whamcloud.com/#/c/9369/

this is wrong because callers rely on +ve to identify blocked
message which is not a failure.

To respect linux kernel coding style and not use positive error
code, this patch adds two macros as non-error returned values of
these functions:
    LNET_CREDIT_OK    has credit for message
    LNET_CREDIT_WAIT  no credit and message is blocked

both these functions will return these two values instead of 0
and EAGAIN
Signed-off-by: Liang Zhen <liang.zhen@intel.com>
Signed-off-by: James Simmons <uja.ornl@gmail.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-5151
Reviewed-on: http://review.whamcloud.com/10625Reviewed-by: Chris Horn <hornc@cray.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lnet/lnet/lib-move.c

@@ -42,6 +42,11 @@
 
 #include "../../include/linux/lnet/lib-lnet.h"
 
+/** lnet message has credit and can be submitted to lnd for send/receive */
+#define LNET_CREDIT_OK		0
+/** lnet message is waiting for credit */
+#define LNET_CREDIT_WAIT	1
+
 static int local_nid_dist_zero = 1;
 module_param(local_nid_dist_zero, int, 0444);
 MODULE_PARM_DESC(local_nid_dist_zero, "Reserved");
@@ -786,10 +791,10 @@ lnet_peer_alive_locked(lnet_peer_t *lp)
  *	  lnet_send() is going to lnet_net_unlock immediately after this, so
  *	  it sets do_send FALSE and I don't do the unlock/send/lock bit.
  *
- * \retval 0 If \a msg sent or OK to send.
- * \retval EAGAIN If \a msg blocked for credit.
- * \retval EHOSTUNREACH If the next hop of the message appears dead.
- * \retval ECANCELED If the MD of the message has been unlinked.
+ * \retval LNET_CREDIT_OK If \a msg sent or OK to send.
+ * \retval LNET_CREDIT_WAIT If \a msg blocked for credit.
+ * \retval -EHOSTUNREACH If the next hop of the message appears dead.
+ * \retval -ECANCELED If the MD of the message has been unlinked.
  */
 static int
 lnet_post_send_locked(lnet_msg_t *msg, int do_send)
@@ -817,7 +822,7 @@ lnet_post_send_locked(lnet_msg_t *msg, int do_send)
 			lnet_finalize(ni, msg, -EHOSTUNREACH);
 
 		lnet_net_lock(cpt);
-		return EHOSTUNREACH;
+		return -EHOSTUNREACH;
 	}
 
 	if (msg->msg_md &&
@@ -830,7 +835,7 @@ lnet_post_send_locked(lnet_msg_t *msg, int do_send)
 			lnet_finalize(ni, msg, -ECANCELED);
 
 		lnet_net_lock(cpt);
-		return ECANCELED;
+		return -ECANCELED;
 	}
 
 	if (!msg->msg_peertxcredit) {
@@ -847,7 +852,7 @@ lnet_post_send_locked(lnet_msg_t *msg, int do_send)
 		if (lp->lp_txcredits < 0) {
 			msg->msg_tx_delayed = 1;
 			list_add_tail(&msg->msg_list, &lp->lp_txq);
-			return EAGAIN;
+			return LNET_CREDIT_WAIT;
 		}
 	}
 
@@ -864,7 +869,7 @@ lnet_post_send_locked(lnet_msg_t *msg, int do_send)
 		if (tq->tq_credits < 0) {
 			msg->msg_tx_delayed = 1;
 			list_add_tail(&msg->msg_list, &tq->tq_delayed);
-			return EAGAIN;
+			return LNET_CREDIT_WAIT;
 		}
 	}
 
@@ -873,7 +878,7 @@ lnet_post_send_locked(lnet_msg_t *msg, int do_send)
 		lnet_ni_send(ni, msg);
 		lnet_net_lock(cpt);
 	}
-	return 0;
+	return LNET_CREDIT_OK;
 }
 
 static lnet_rtrbufpool_t *
@@ -901,8 +906,9 @@ lnet_post_routed_recv_locked(lnet_msg_t *msg, int do_recv)
 {
 	/*
 	 * lnet_parse is going to lnet_net_unlock immediately after this, so it
-	 * sets do_recv FALSE and I don't do the unlock/send/lock bit.  I
-	 * return EAGAIN if msg blocked and 0 if received or OK to receive
+	 * sets do_recv FALSE and I don't do the unlock/send/lock bit.
+	 * I return LNET_CREDIT_WAIT if msg blocked and LNET_CREDIT_OK if
+	 * received or OK to receive
 	 */
 	lnet_peer_t *lp = msg->msg_rxpeer;
 	lnet_rtrbufpool_t *rbp;
@@ -932,7 +938,7 @@ lnet_post_routed_recv_locked(lnet_msg_t *msg, int do_recv)
 			LASSERT(msg->msg_rx_ready_delay);
 			msg->msg_rx_delayed = 1;
 			list_add_tail(&msg->msg_list, &lp->lp_rtrq);
-			return EAGAIN;
+			return LNET_CREDIT_WAIT;
 		}
 	}
 
@@ -952,7 +958,7 @@ lnet_post_routed_recv_locked(lnet_msg_t *msg, int do_recv)
 			LASSERT(msg->msg_rx_ready_delay);
 			msg->msg_rx_delayed = 1;
 			list_add_tail(&msg->msg_list, &rbp->rbp_msgs);
-			return EAGAIN;
+			return LNET_CREDIT_WAIT;
 		}
 	}
 
@@ -971,7 +977,7 @@ lnet_post_routed_recv_locked(lnet_msg_t *msg, int do_recv)
 			     0, msg->msg_len, msg->msg_len);
 		lnet_net_lock(cpt);
 	}
-	return 0;
+	return LNET_CREDIT_OK;
 }
 
 void
@@ -1360,13 +1366,13 @@ lnet_send(lnet_nid_t src_nid, lnet_msg_t *msg, lnet_nid_t rtr_nid)
 	rc = lnet_post_send_locked(msg, 0);
 	lnet_net_unlock(cpt);
 
-	if (rc == EHOSTUNREACH || rc == ECANCELED)
-		return -rc;
+	if (rc < 0)
+		return rc;
 
-	if (!rc)
+	if (rc == LNET_CREDIT_OK)
 		lnet_ni_send(src_ni, msg);
 
-	return 0; /* !rc or EAGAIN */
+	return 0; /* rc == LNET_CREDIT_OK or LNET_CREDIT_WAIT */
 }
 
 static void
@@ -1630,6 +1636,11 @@ lnet_parse_ack(lnet_ni_t *ni, lnet_msg_t *msg)
 	return 0;
 }
 
+/**
+ * \retval LNET_CREDIT_OK	If \a msg is forwarded
+ * \retval LNET_CREDIT_WAIT	If \a msg is blocked because w/o buffer
+ * \retval -ve			error code
+ */
 static int
 lnet_parse_forward_locked(lnet_ni_t *ni, lnet_msg_t *msg)
 {
@@ -1921,7 +1932,8 @@ lnet_parse(lnet_ni_t *ni, lnet_hdr_t *hdr, lnet_nid_t from_nid,
 
 		if (rc < 0)
 			goto free_drop;
-		if (!rc) {
+
+		if (rc == LNET_CREDIT_OK) {
 			lnet_ni_recv(ni, msg->msg_private, msg, 0,
 				     0, payload_length, payload_length);
 		}