afs: Log remote unmarshalling errors

Log unmarshalling errors reported by the peer (ie. it can't parse what we
sent it).  Limit the maximum number of messages to 3.
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-By: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
Link: https://lore.kernel.org/r/159465826250.1377938.16372395422217583913.stgit@warthog.procyon.org.uk/
Link: https://lore.kernel.org/r/160588532584.3465195.15618385466614028590.stgit@warthog.procyon.org.uk/ # rfc
Link: https://lore.kernel.org/r/161118149739.1232039.208060911149801695.stgit@warthog.procyon.org.uk/ # rfc
Link: https://lore.kernel.org/r/161161046033.2537118.7779717661044373273.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/161340409118.1303470.17812607349396199116.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/161539552964.286939.16503232687974398308.stgit@warthog.procyon.org.uk/ # v4
Link: https://lore.kernel.org/r/161653808989.2770958.11530765353025697860.stgit@warthog.procyon.org.uk/ # v5
Link: https://lore.kernel.org/r/161789092349.6155.8581594259882708631.stgit@warthog.procyon.org.uk/ # v6

fs/afs/rxrpc.c

@@ -500,6 +500,39 @@ void afs_make_call(struct afs_addr_cursor *ac, struct afs_call *call, gfp_t gfp)
 	_leave(" = %d", ret);
 }
 
+/*
+ * Log remote abort codes that indicate that we have a protocol disagreement
+ * with the server.
+ */
+static void afs_log_error(struct afs_call *call, s32 remote_abort)
+{
+	static int max = 0;
+	const char *msg;
+	int m;
+
+	switch (remote_abort) {
+	case RX_EOF:		 msg = "unexpected EOF";	break;
+	case RXGEN_CC_MARSHAL:	 msg = "client marshalling";	break;
+	case RXGEN_CC_UNMARSHAL: msg = "client unmarshalling";	break;
+	case RXGEN_SS_MARSHAL:	 msg = "server marshalling";	break;
+	case RXGEN_SS_UNMARSHAL: msg = "server unmarshalling";	break;
+	case RXGEN_DECODE:	 msg = "opcode decode";		break;
+	case RXGEN_SS_XDRFREE:	 msg = "server XDR cleanup";	break;
+	case RXGEN_CC_XDRFREE:	 msg = "client XDR cleanup";	break;
+	case -32:		 msg = "insufficient data";	break;
+	default:
+		return;
+	}
+
+	m = max;
+	if (m < 3) {
+		max = m + 1;
+		pr_notice("kAFS: Peer reported %s failure on %s [%pISp]\n",
+			  msg, call->type->name,
+			  &call->alist->addrs[call->addr_ix].transport);
+	}
+}
+
 /*
  * deliver messages to a call
  */
@@ -563,6 +596,7 @@ static void afs_deliver_to_call(struct afs_call *call)
 			goto out;
 		case -ECONNABORTED:
 			ASSERTCMP(state, ==, AFS_CALL_COMPLETE);
+			afs_log_error(call, call->abort_code);
 			goto done;
 		case -ENOTSUPP:
 			abort_code = RXGEN_OPCODE;