Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753503AbbEGKAV (ORCPT ); Thu, 7 May 2015 06:00:21 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:48197 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753027AbbEGJuJ (ORCPT ); Thu, 7 May 2015 05:50:09 -0400 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Alexander Duyck , "David S. Miller" , Luis Henriques Subject: [PATCH 3.16.y-ckt 160/180] jhash: Update jhash_[321]words functions to use correct initval Date: Thu, 7 May 2015 10:46:09 +0100 Message-Id: <1430991989-23170-161-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1430991989-23170-1-git-send-email-luis.henriques@canonical.com> References: <1430991989-23170-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2885 Lines: 79 3.16.7-ckt11 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Alexander Duyck commit 2e7056c433216f406b90a003aa0ba42e19d3bdcf upstream. Looking over the implementation for jhash2 and comparing it to jhash_3words I realized that the two hashes were in fact very different. Doing a bit of digging led me to "The new jhash implementation" in which lookup2 was supposed to have been replaced with lookup3. In reviewing the patch I noticed that jhash2 had originally initialized a and b to JHASH_GOLDENRATIO and c to initval, but after the patch a, b, and c were initialized to initval + (length << 2) + JHASH_INITVAL. However the changes in jhash_3words simply replaced the initialization of a and b with JHASH_INITVAL. This change corrects what I believe was an oversight so that a, b, and c in jhash_3words all have the same value added consisting of initval + (length << 2) + JHASH_INITVAL so that jhash2 and jhash_3words will now produce the same hash result given the same inputs. Fixes: 60d509c823cca ("The new jhash implementation") Signed-off-by: Alexander Duyck Signed-off-by: David S. Miller Signed-off-by: Luis Henriques --- include/linux/jhash.h | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/include/linux/jhash.h b/include/linux/jhash.h index 47cb09edec1a..348c6f47e4cc 100644 --- a/include/linux/jhash.h +++ b/include/linux/jhash.h @@ -145,11 +145,11 @@ static inline u32 jhash2(const u32 *k, u32 length, u32 initval) } -/* jhash_3words - hash exactly 3, 2 or 1 word(s) */ -static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval) +/* __jhash_nwords - hash exactly 3, 2 or 1 word(s) */ +static inline u32 __jhash_nwords(u32 a, u32 b, u32 c, u32 initval) { - a += JHASH_INITVAL; - b += JHASH_INITVAL; + a += initval; + b += initval; c += initval; __jhash_final(a, b, c); @@ -157,14 +157,19 @@ static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval) return c; } +static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval) +{ + return __jhash_nwords(a, b, c, initval + JHASH_INITVAL + (3 << 2)); +} + static inline u32 jhash_2words(u32 a, u32 b, u32 initval) { - return jhash_3words(a, b, 0, initval); + return __jhash_nwords(a, b, 0, initval + JHASH_INITVAL + (2 << 2)); } static inline u32 jhash_1word(u32 a, u32 initval) { - return jhash_3words(a, 0, 0, initval); + return __jhash_nwords(a, 0, 0, initval + JHASH_INITVAL + (1 << 2)); } #endif /* _LINUX_JHASH_H */ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/