netdev - [PATCH v2] net: sctp: Don't use 64 kilobyte lookup table for four elements

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Date:	Mon, 28 Sep 2015 14:34:04 +0200
From:	Denys Vlasenko <dvlasenk@...hat.com>
To:	"David S. Miller" <davem@...emloft.net>
Cc:	Denys Vlasenko <dvlasenk@...hat.com>,
	Vlad Yasevich <vyasevich@...il.com>,
	Neil Horman <nhorman@...driver.com>,
	Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
	linux-sctp@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2] net: sctp: Don't use 64 kilobyte lookup table for four elements

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@...hat.com>
CC: Vlad Yasevich <vyasevich@...il.com>
CC: Neil Horman <nhorman@...driver.com>
CC: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
CC: linux-sctp@...r.kernel.org
CC: netdev@...r.kernel.org
CC: linux-kernel@...r.kernel.org
---

Changes since v1: tweaked comments

 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 */
+	}
 }
 
 static struct sctp_transport *sctp_trans_elect_tie(struct sctp_transport *trans1,
-- 
1.8.1.4

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