From patchwork Mon Apr 6 20:18:25 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tejun Heo X-Patchwork-Id: 6165401 Return-Path: X-Original-To: patchwork-linux-fsdevel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 8E689BF4A6 for ; Mon, 6 Apr 2015 20:20:14 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id A643B2034B for ; Mon, 6 Apr 2015 20:20:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B8E0F20303 for ; Mon, 6 Apr 2015 20:20:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754611AbbDFUUK (ORCPT ); Mon, 6 Apr 2015 16:20:10 -0400 Received: from mail-qc0-f182.google.com ([209.85.216.182]:34090 "EHLO mail-qc0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754053AbbDFUSp (ORCPT ); Mon, 6 Apr 2015 16:18:45 -0400 Received: by qcyk17 with SMTP id k17so15417134qcy.1; Mon, 06 Apr 2015 13:18:45 -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=WPLmDXwDnIT+uQDa2ct1ZDN5w/Yf41h1ZUgaGIv/ARM=; b=RjM2H+GYxT7/EKcnR+s5+D2xCJLUWu8DSPvhX3rrl4eVFPXbKMlsqxtbNzLMjGpNE4 lqgEZrQivYriQWLCIvTytJCBVPomYL5mP0ROlrwnwC1IBsslYM1KyHwlYMsiIX1WJ9JX 3zUccpFmCIrEQozpjtFqOJ66zfa+xGg80mnr6LThGAgT1S1m76AMNaXt56TarOBruCKR 1G4ti7rIcpprLISikkXHSH1BpGqaKv2CcnDaxahh33f71wQki/gaWqFnhE+yz+RAq6xp H6HpgsaXUcGJFcPy7HoHJMPGn0FEcDcATUQKM4a0+kXS4VJJn2We+wDGz8qfobMwifou aBfw== X-Received: by 10.140.149.132 with SMTP id 126mr20280797qhv.38.1428351525034; Mon, 06 Apr 2015 13:18:45 -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 75sm3868673qhw.41.2015.04.06.13.18.43 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 06 Apr 2015 13:18:43 -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, Tejun Heo Subject: [PATCH 07/10] writeback: use unlocked_inode_to_wb transaction in inode_congested() Date: Mon, 6 Apr 2015 16:18:25 -0400 Message-Id: <1428351508-8399-8-git-send-email-tj@kernel.org> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1428351508-8399-1-git-send-email-tj@kernel.org> References: <1428351508-8399-1-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 97fb7f3..ee65ff09 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -596,10 +596,18 @@ 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);