>>
>> Thanks for your review, Neil!
>>
>> I know what you mean, yes, it's most probably that the searched TSN was
>> transmitted in the currently active_path, but what should we do if not.
>>
>> Check the comment in sctp_assoc_lookup_tsn() function:
>> /* Let's be hopeful and check the active_path first. */
>> /* If not found, go search all the other transports. */
>>
>> It has checked the active_path first and then traverse all the other
>> transports in
>> the transport_addr_list except the active_path.
>>
>> So what I want to fix here is the inconsistency between the function
>> should do and
>> the code actually does.
>>
> I understand what you're doing, and I agree that the fix is functional
> (Hence
> my "This works" statement in my last note). What I'm suggesting is that,
> since
> you're messing about in that code anyway that you clean it up while your at
> it,
> so that we don't need to have the if (transport == active) check at all.
> We
> trade in some extra work in a non-critical path (sctp_assoc_set_primary),
> for
> the removal of an extra for loop operation and a conditional check in a
> much
> hotter path. Something like this (completely untested), is what I was
> thinking
Aha, seems I have some misunderstanding previously, now I got your point.
Yeah, it's better to do the clean up by this way, and this fix looks fine to me,
but I didn't have a test case to test this, actually this problem was detected
by code review, so I would like to leave the rest of this work to
determine by you.
Thank you very much for your clarification!
Thanks,
Xufeng
>
>
> diff --git a/net/sctp/associola.c b/net/sctp/associola.c
> index 43cd0dd..8ae873c 100644
> --- a/net/sctp/associola.c
> +++ b/net/sctp/associola.c
> @@ -505,6 +505,9 @@ void sctp_assoc_set_primary(struct sctp_association
> *asoc,
>
> asoc->peer.primary_path = transport;
>
> + list_del_rcu(&transport->transports);
> + list_add_rcu(&transport->transports, &asoc->peer.transport_addr_list);
> +
> /* Set a default msg_name for events. */
> memcpy(&asoc->peer.primary_addr, &transport->ipaddr,
> sizeof(union sctp_addr));
> @@ -1040,7 +1043,6 @@ struct sctp_chunk *sctp_get_ecne_prepend(struct
> sctp_association *asoc)
> struct sctp_transport *sctp_assoc_lookup_tsn(struct sctp_association
> *asoc,
> __u32 tsn)
> {
> - struct sctp_transport *active;
> struct sctp_transport *match;
> struct sctp_transport *transport;
> struct sctp_chunk *chunk;
> @@ -1057,29 +1059,16 @@ struct sctp_transport *sctp_assoc_lookup_tsn(struct
> sctp_association *asoc,
> * The general strategy is to search each transport's transmitted
> * list. Return which transport this TSN lives on.
> *
> - * Let's be hopeful and check the active_path first.
> - * Another optimization would be to know if there is only one
> - * outbound path and not have to look for the TSN at all.
> + * Note, that sctp_assoc_set_primary does a move to front operation
> + * on the active_path transport, so this code implicitly checks
> + * the active_path first, as we most commonly expect to find our TSN
> + * there.
> *
> */
>
> - active = asoc->peer.active_path;
> -
> - list_for_each_entry(chunk, &active->transmitted,
> - transmitted_list) {
> -
> - if (key == chunk->subh.data_hdr->tsn) {
> - match = active;
> - goto out;
> - }
> - }
> -
> - /* If not found, go search all the other transports. */
> list_for_each_entry(transport, &asoc->peer.transport_addr_list,
> transports) {
>
> - if (transport == active)
> - break;
> list_for_each_entry(chunk, &transport->transmitted,
> transmitted_list) {
> if (key == chunk->subh.data_hdr->tsn) {
>
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