sctp: Optimize SFR-CACC transport list walking during SACK processing

There is a possibility of walking the transport list twice during
SACK processing when doing SFR-CACC algorithm.  We can restructure
the code to only do this once.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>

diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
index ef5ea74..c8de4da 100644 (file)
--- a/net/sctp/outqueue.c
+++ b/net/sctp/outqueue.c
@@ -1145,27 +1145,31 @@ int sctp_outq_sack(struct sctp_outq *q, struct sctp_sackhdr *sack)
         * on the current primary, the CHANGEOVER_ACTIVE flag SHOULD be
         * cleared. The CYCLING_CHANGEOVER flag SHOULD also be cleared for
         * all destinations.
-        */
-       if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
-               primary->cacc.changeover_active = 0;
-               list_for_each_entry(transport, transport_list,
-                               transports) {
-                       transport->cacc.cycling_changeover = 0;
-               }
-       }
-
-       /*
-        * SFR-CACC algorithm:
         * 2) If the SACK contains gap acks and the flag CHANGEOVER_ACTIVE
         * is set the receiver of the SACK MUST take the following actions:
         *
         * A) Initialize the cacc_saw_newack to 0 for all destination
         * addresses.
+        *
+        * Only bother if changeover_active is set. Otherwise, this is
+        * totally suboptimal to do on every SACK.
         */
-       if (gap_ack_blocks &&
-           primary->cacc.changeover_active) {
-               list_for_each_entry(transport, transport_list, transports) {
-                       transport->cacc.cacc_saw_newack = 0;
+       if (primary->cacc.changeover_active) {
+               u8 clear_cycling = 0;
+
+               if (TSN_lte(primary->cacc.next_tsn_at_change, sack_ctsn)) {
+                       primary->cacc.changeover_active = 0;
+                       clear_cycling = 1;
+               }
+
+               if (clear_cycling || gap_ack_blocks) {
+                       list_for_each_entry(transport, transport_list,
+                                       transports) {
+                               if (clear_cycling)
+                                       transport->cacc.cycling_changeover = 0;
+                               if (gap_ack_blocks)
+                                       transport->cacc.cacc_saw_newack = 0;
+                       }
                }
        }