From: Chris Horn <chris.horn@hpe.com>
Date: Wed, 1 Jun 2022 02:19:07 +0000 (-0500)
Subject: LU-15929 lnet: Correct net selection for router ping
X-Git-Tag: 2.15.52~62
X-Git-Url: https://git.whamcloud.com/?p=fs%2Flustre-release.git;a=commitdiff_plain;h=2431e099b143a4c7e7f951c912263f1536db07f0

LU-15929 lnet: Correct net selection for router ping

lnet_find_best_ni_on_local_net() contains logic for restricting
the NI selection to a net specified by lnet_peer::lp_disc_net_id. The
purpose of this is to ensure that LNet peers ping every interface on
a router at a regular interval as part of the LNet router health
feature. However, this logic is flawed because lnet_msg_discovery()
is used to determine whether the message being sent is a discovery
message, but that function actually determines whether a given message
can _trigger_ discovery.

Introduce a new function, lnet_msg_is_ping(), which determines whether
a given lnet_msg is a GET on the LNET_RESERVED_PORTAL.
Modify lnet_find_best_ni_on_local_net() to restrict NI selection to
lp_disc_net_id iff:
1. lp_disc_net_id is non-zero
2. The peer has the LNET_PEER_RTR_DISCOVERY flag set.
3. lnet_msg_is_ping() returns true

Test-Parameters: trivial testlist=sanity-lnet
HPE-bug-id: LUS-11017
Signed-off-by: Chris Horn <chris.horn@hpe.com>
Change-Id: I3dbdfd5c44b6167d24b7b6e0b1097db0b3c5cb76
Reviewed-on: https://review.whamcloud.com/47527
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Frank Sehr <fsehr@whamcloud.com>
Reviewed-by: Cyril Bordage <cbordage@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
---

diff --git a/lnet/lnet/lib-move.c b/lnet/lnet/lib-move.c
index 2a30af8..e23a532 100644
--- a/lnet/lnet/lib-move.c
+++ b/lnet/lnet/lib-move.c
@@ -1762,7 +1762,8 @@ lnet_reserved_msg(struct lnet_msg *msg)
 	return false;
 }
 
-/*
+/* Can the specified message trigger peer discovery?
+ *
  * Traffic to the LNET_RESERVED_PORTAL may not trigger peer discovery,
  * because such traffic is required to perform discovery. We therefore
  * exclude all GET and PUT on that portal. We also exclude all ACK and
@@ -1776,6 +1777,18 @@ lnet_msg_discovery(struct lnet_msg *msg)
 	return !(lnet_reserved_msg(msg) || lnet_msg_is_response(msg));
 }
 
+/* Is the specified message an LNet ping?
+ */
+static bool
+lnet_msg_is_ping(struct lnet_msg *msg)
+{
+	if (msg->msg_type == LNET_MSG_GET &&
+	    msg->msg_hdr.msg.get.ptl_index == LNET_RESERVED_PORTAL)
+		return true;
+
+	return false;
+}
+
 #define SRC_SPEC	0x0001
 #define SRC_ANY		0x0002
 #define LOCAL_DST	0x0004
@@ -2432,10 +2445,14 @@ lnet_find_best_ni_on_local_net(struct lnet_peer *peer, int md_cpt,
 	__u32 best_net_sel_prio = LNET_MAX_SELECTION_PRIORITY;
 	__u32 net_sel_prio;
 
-	/* if this is a discovery message and lp_disc_net_id is
-	 * specified then use that net to send the discovery on.
+	/* If lp_disc_net_id is set, this peer is a router undergoing
+	 * discovery, and this message is an LNet ping, then this may be a
+	 * discovery message and we need to select an NI on the peer net
+	 * specified by lp_disc_net_id
 	 */
-	if (discovery && peer->lp_disc_net_id) {
+	if (peer->lp_disc_net_id &&
+	    (peer->lp_state & LNET_PEER_RTR_DISCOVERY) &&
+	    lnet_msg_is_ping(msg)) {
 		best_lpn = lnet_peer_get_net_locked(peer, peer->lp_disc_net_id);
 		if (best_lpn && lnet_get_net_locked(best_lpn->lpn_net_id))
 			goto select_best_ni;