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SubjectRe: [PATCH] net: sctp: Don't use 64 kilobyte lookup table for four elements
On Sat, Sep 26, 2015 at 08:53:14PM +0200, Denys Vlasenko wrote:
> Seemingly innocuous sctp_trans_state_to_prio_map[] array
> is way bigger than it looks, since
> "[SCTP_UNKNOWN] = 2" expands into "[0xffff] = 2" !
>
> This patch replaces it with switch() statement.
>
> Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
> CC: Vlad Yasevich <vyasevich@gmail.com>
> CC: Neil Horman <nhorman@tuxdriver.com>
> CC: linux-sctp@vger.kernel.org
> CC: linux-kernel@vger.kernel.org
> ---
> net/sctp/associola.c | 20 +++++++++++---------
> 1 file changed, 11 insertions(+), 9 deletions(-)
>
> diff --git a/net/sctp/associola.c b/net/sctp/associola.c
> index 197c3f5..dae51ac 100644
> --- a/net/sctp/associola.c
> +++ b/net/sctp/associola.c
> @@ -1208,20 +1208,22 @@ void sctp_assoc_update(struct sctp_association *asoc,
> * within this document.
> *
> * Our basic strategy is to round-robin transports in priorities
> - * according to sctp_state_prio_map[] e.g., if no such
> + * according to sctp_trans_score() e.g., if no such
> * transport with state SCTP_ACTIVE exists, round-robin through
> * SCTP_UNKNOWN, etc. You get the picture.
> */
> -static const u8 sctp_trans_state_to_prio_map[] = {
> - [SCTP_ACTIVE] = 3, /* best case */
> - [SCTP_UNKNOWN] = 2,
> - [SCTP_PF] = 1,
> - [SCTP_INACTIVE] = 0, /* worst case */
> -};
> -
> static u8 sctp_trans_score(const struct sctp_transport *trans)
> {
> - return sctp_trans_state_to_prio_map[trans->state];
> + switch (trans->state) {
> + case SCTP_ACTIVE:
> + return 3; /* best case */
> + case SCTP_UNKNOWN:
> + return 2;
> + case SCTP_PF:
> + return 1;
> + default: /* case SCTP_INACTIVE */
> + return 0; /* worst case */
> + }
> }

Nice finding, but please make above comments aligned to the column.
Then it looks good to me.

When posting v2, also post to netdev@vger.kernel.org, it's where Dave
collects sctp (amongst others) patches. Kernel patches are not collected
on linux-sctp@, though they are posted there too but for reviewing only.

Thanks,
Marcelo


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