From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7EDD5C2D0DB for ; Wed, 29 Jan 2020 18:24:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 61AD2206F0 for ; Wed, 29 Jan 2020 18:24:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727482AbgA2SYr (ORCPT ); Wed, 29 Jan 2020 13:24:47 -0500 Received: from mx2.suse.de ([195.135.220.15]:45752 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727107AbgA2SYr (ORCPT ); Wed, 29 Jan 2020 13:24:47 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 5F52DAECB; Wed, 29 Jan 2020 18:24:45 +0000 (UTC) From: Davidlohr Bueso To: song@kernel.org Cc: linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, dave@stgolabs.net, Davidlohr Bueso Subject: [PATCH] md: optimize barrier usage for Rmw atomic bitops Date: Wed, 29 Jan 2020 10:14:37 -0800 Message-Id: <20200129181437.25155-1-dave@stgolabs.net> X-Mailer: git-send-email 2.16.4 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org For both set and clear_bit, we can avoid the unnecessary barrier on non LL/SC architectures, such as x86. Instead, use the smp_mb__{before,after}_atomic() calls. Signed-off-by: Davidlohr Bueso --- drivers/md/md.c | 2 +- drivers/md/raid10.c | 7 ++++--- drivers/md/raid5.c | 9 +++++---- 3 files changed, 10 insertions(+), 8 deletions(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index 4824d50526fa..4ed2eb6933f7 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -2561,7 +2561,7 @@ static bool set_in_sync(struct mddev *mddev) * Ensure ->in_sync is visible before we clear * ->sync_checkers. */ - smp_mb(); + smp_mb__before_atomic(); set_bit(MD_SB_CHANGE_CLEAN, &mddev->sb_flags); sysfs_notify_dirent_safe(mddev->sysfs_state); } diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c index ec136e44aef7..1993a1958c75 100644 --- a/drivers/md/raid10.c +++ b/drivers/md/raid10.c @@ -1865,9 +1865,10 @@ static int raid10_remove_disk(struct mddev *mddev, struct md_rdev *rdev) /* We must have just cleared 'rdev' */ p->rdev = p->replacement; clear_bit(Replacement, &p->replacement->flags); - smp_mb(); /* Make sure other CPUs may see both as identical - * but will never see neither -- if they are careful. - */ + /* Make sure other CPUs may see both as identical + * but will never see neither -- if they are careful. + */ + smp_mb__after_atomic(); p->replacement = NULL; } diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index ba00e9877f02..3ad6209287cf 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -364,7 +364,7 @@ static int release_stripe_list(struct r5conf *conf, int hash; /* sh could be readded after STRIPE_ON_RELEASE_LIST is cleard */ - smp_mb(); + smp_mb__before_atomic(); clear_bit(STRIPE_ON_RELEASE_LIST, &sh->state); /* * Don't worry the bit is set here, because if the bit is set @@ -7654,9 +7654,10 @@ static int raid5_remove_disk(struct mddev *mddev, struct md_rdev *rdev) /* We must have just cleared 'rdev' */ p->rdev = p->replacement; clear_bit(Replacement, &p->replacement->flags); - smp_mb(); /* Make sure other CPUs may see both as identical - * but will never see neither - if they are careful - */ + /* Make sure other CPUs may see both as identical + * but will never see neither - if they are careful + */ + smp_mb__after_atomic(); p->replacement = NULL; if (!err) -- 2.16.4