From patchwork Thu Feb 20 10:08:55 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Miao Xie X-Patchwork-Id: 3685631 Return-Path: X-Original-To: patchwork-linux-btrfs@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 9B8289F1EE for ; Thu, 20 Feb 2014 10:07:49 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id C9EB320181 for ; Thu, 20 Feb 2014 10:07:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E93F02011D for ; Thu, 20 Feb 2014 10:07:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752424AbaBTKHo (ORCPT ); Thu, 20 Feb 2014 05:07:44 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:12170 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1752316AbaBTKHi (ORCPT ); Thu, 20 Feb 2014 05:07:38 -0500 X-IronPort-AV: E=Sophos;i="4.97,511,1389715200"; d="scan'208";a="9567793" Received: from unknown (HELO tang.cn.fujitsu.com) ([10.167.250.3]) by song.cn.fujitsu.com with ESMTP; 20 Feb 2014 18:03:45 +0800 Received: from fnstmail02.fnst.cn.fujitsu.com (tang.cn.fujitsu.com [127.0.0.1]) by tang.cn.fujitsu.com (8.14.3/8.13.1) with ESMTP id s1KA7YYM011826 for ; Thu, 20 Feb 2014 18:07:35 +0800 Received: from miao.fnst.cn.fujitsu.com ([10.167.226.201]) by fnstmail02.fnst.cn.fujitsu.com (Lotus Domino Release 8.5.3) with ESMTP id 2014022018052289-73088 ; Thu, 20 Feb 2014 18:05:22 +0800 From: Miao Xie To: linux-btrfs@vger.kernel.org Subject: [PATCH 5/9] Btrfs: remove unnecessary memory barrier in btrfs_sync_log() Date: Thu, 20 Feb 2014 18:08:55 +0800 Message-Id: <1392890939-19044-5-git-send-email-miaox@cn.fujitsu.com> X-Mailer: git-send-email 1.8.5.3 In-Reply-To: <1392890939-19044-1-git-send-email-miaox@cn.fujitsu.com> References: <1392890939-19044-1-git-send-email-miaox@cn.fujitsu.com> X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2014/02/20 18:05:22, Serialize by Router on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2014/02/20 18:05:24, Serialize complete at 2014/02/20 18:05:24 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org X-Spam-Status: No, score=-7.5 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Mutex unlock implies certain memory barriers to make sure all the memory operation completes before the unlock, and the next mutex lock implies memory barriers to make sure the all the memory happens after the lock. So it is a full memory barrier(smp_mb), we needn't add memory barriers. Remove them. Signed-off-by: Miao Xie --- fs/btrfs/tree-log.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c index 51d1bd9..c9f2479 100644 --- a/fs/btrfs/tree-log.c +++ b/fs/btrfs/tree-log.c @@ -2497,7 +2497,6 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans, root->log_transid++; log->log_transid = root->log_transid; root->log_start_pid = 0; - smp_mb(); /* * IO has been started, blocks of the log tree have WRITTEN flag set * in their headers. new modifications of the log will be written to @@ -2590,8 +2589,6 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans, btrfs_header_level(log_root_tree->node)); log_root_tree->log_transid++; - smp_mb(); - mutex_unlock(&log_root_tree->log_mutex); /*