From patchwork Fri May 22 22:36:20 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tejun Heo X-Patchwork-Id: 6469651 Return-Path: X-Original-To: patchwork-linux-fsdevel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id D48A59F444 for ; Fri, 22 May 2015 22:38:12 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 04C2A20546 for ; Fri, 22 May 2015 22:38:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0C15A20544 for ; Fri, 22 May 2015 22:38:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161045AbbEVWhy (ORCPT ); Fri, 22 May 2015 18:37:54 -0400 Received: from mail-qg0-f49.google.com ([209.85.192.49]:35576 "EHLO mail-qg0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1946246AbbEVWgj (ORCPT ); Fri, 22 May 2015 18:36:39 -0400 Received: by qgew3 with SMTP id w3so17204788qge.2; Fri, 22 May 2015 15:36:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:from:to:cc:subject:date:message-id:in-reply-to:references; bh=4XPPzzZj/rl+j01RFxtK+9X690aH68yk8FfxlQWonU4=; b=zlZEU5e5BpeeZ1Pr3LXUsBbDBF4+mMHa/1aPgpr2mWQtsS2sOtYBJM62inPs/2C+/1 T+8raL2G9sIhmKWQmcjzOwf5dHh3FFl8Nvp3l8Own0++ZWbQsgSi0KodsZrqVeIkyeQG C6FTvLnV/zRCvtuCnQi9UhiTWeSHFU+nlyIRHaNdTNFhf8iqrTS7oN/ys5PMY4u9REFO 7ZikN8bZHvu21/5VGF5RRLGH42xcL9L+IhW8BJ4etqm/yi+AMVJ0PFiVcOwjoyi2fRXV psSOZxrCnigXPl7uotchNwhbVlVjBz6mh4gK+71oyB2ST3nZb1iRgCLo1VrwmOaYnota gffg== X-Received: by 10.140.235.11 with SMTP id g11mr3380768qhc.34.1432334198512; Fri, 22 May 2015 15:36:38 -0700 (PDT) Received: from htj.duckdns.org.lan (207-38-238-8.c3-0.wsd-ubr1.qens-wsd.ny.cable.rcn.com. [207.38.238.8]) by mx.google.com with ESMTPSA id m48sm2192635qgd.35.2015.05.22.15.36.36 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 22 May 2015 15:36:37 -0700 (PDT) From: Tejun Heo To: axboe@kernel.dk Cc: linux-kernel@vger.kernel.org, jack@suse.cz, hch@infradead.org, hannes@cmpxchg.org, linux-fsdevel@vger.kernel.org, vgoyal@redhat.com, lizefan@huawei.com, cgroups@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.cz, clm@fb.com, fengguang.wu@intel.com, david@fromorbit.com, gthelen@google.com, khlebnikov@yandex-team.ru, Tejun Heo Subject: [PATCH 6/9] writeback: use unlocked_inode_to_wb transaction in inode_congested() Date: Fri, 22 May 2015 18:36:20 -0400 Message-Id: <1432334183-6324-7-git-send-email-tj@kernel.org> X-Mailer: git-send-email 2.4.0 In-Reply-To: <1432334183-6324-1-git-send-email-tj@kernel.org> References: <1432334183-6324-1-git-send-email-tj@kernel.org> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Spam-Status: No, score=-6.8 required=5.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_HI,T_DKIM_INVALID,T_RP_MATCHES_RCVD,UNPARSEABLE_RELAY autolearn=ham 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 Similar to wb stat updates, inode_congested() accesses the associated wb of an inode locklessly, which will break with foreign inode wb switching. This path updates inode_congested() to use unlocked inode wb access transaction introduced by the previous patch. Combined with the previous two patches, this makes all wb list and access operations to be protected by either of inode->i_lock, wb->list_lock, or mapping->tree_lock while wb switching is in progress. Signed-off-by: Tejun Heo Cc: Jens Axboe Cc: Jan Kara Cc: Wu Fengguang Cc: Greg Thelen --- fs/fs-writeback.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 118e9c4..eb94b00 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -609,10 +609,18 @@ void wbc_account_io(struct writeback_control *wbc, struct page *page, */ int inode_congested(struct inode *inode, int cong_bits) { - if (inode) { - struct bdi_writeback *wb = inode_to_wb(inode); - if (wb) - return wb_congested(wb, cong_bits); + /* + * Once set, ->i_wb never becomes NULL while the inode is alive. + * Start transaction iff ->i_wb is visible. + */ + if (inode && inode_to_wb(inode)) { + struct bdi_writeback *wb; + bool locked, congested; + + wb = unlocked_inode_to_wb_begin(inode, &locked); + congested = wb_congested(wb, cong_bits); + unlocked_inode_to_wb_end(inode, locked); + return congested; } return wb_congested(&inode_to_bdi(inode)->wb, cong_bits);