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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,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 6F797C17441 for ; Mon, 11 Nov 2019 18:47:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 45E6720674 for ; Mon, 11 Nov 2019 18:47:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573498050; bh=ZZD3P9bX6jJOAa0xFQLXVAuNjTf37Uhk8BgWgKMRGgI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=tDQVTrAfzoRYKgbsoWkUeS4h/0LEgYhAfGGl8TT/TDHmdoKA1sOPlio9+wFqje4so FiEpoiWKbp94U83KWkSyNw2lBvB5klb+UgT0Z3Nw7/HcC8FRIaMp5sKzLZDRwC7idd 5jUwUVMQKXx8ZDoMTg1RIGTcSBpZ3aor0WOWMGYQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728988AbfKKSr2 (ORCPT ); Mon, 11 Nov 2019 13:47:28 -0500 Received: from mail.kernel.org ([198.145.29.99]:40156 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730103AbfKKSrW (ORCPT ); Mon, 11 Nov 2019 13:47:22 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 6B13B204FD; Mon, 11 Nov 2019 18:47:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573498042; bh=ZZD3P9bX6jJOAa0xFQLXVAuNjTf37Uhk8BgWgKMRGgI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=B/mtzFXUIPLYGfKv3tplIrYu4L/dTSj8aRXBxarGWfARpFgSK0vWSERj4JtT70rXH HOjLsGPKrk6N2HNGTbMigvmTUCLxi65ooVtvQHiDOtyTrw+mrpROUddufy9KDvaQR3 J9C4cXGJ+NLqKo6vVnn+fvmy3ci3L0uM1e7vnSSU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Konstantin Khlebnikov , Jan Kara , Tejun Heo , Jens Axboe , Johannes Weiner , Andrew Morton , Linus Torvalds Subject: [PATCH 4.19 124/125] mm/filemap.c: dont initiate writeback if mapping has no dirty pages Date: Mon, 11 Nov 2019 19:29:23 +0100 Message-Id: <20191111181456.247399096@linuxfoundation.org> X-Mailer: git-send-email 2.24.0 In-Reply-To: <20191111181438.945353076@linuxfoundation.org> References: <20191111181438.945353076@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Konstantin Khlebnikov commit c3aab9a0bd91b696a852169479b7db1ece6cbf8c upstream. Functions like filemap_write_and_wait_range() should do nothing if inode has no dirty pages or pages currently under writeback. But they anyway construct struct writeback_control and this does some atomic operations if CONFIG_CGROUP_WRITEBACK=y - on fast path it locks inode->i_lock and updates state of writeback ownership, on slow path might be more work. Current this path is safely avoided only when inode mapping has no pages. For example generic_file_read_iter() calls filemap_write_and_wait_range() at each O_DIRECT read - pretty hot path. This patch skips starting new writeback if mapping has no dirty tags set. If writeback is already in progress filemap_write_and_wait_range() will wait for it. Link: http://lkml.kernel.org/r/156378816804.1087.8607636317907921438.stgit@buzz Signed-off-by: Konstantin Khlebnikov Reviewed-by: Jan Kara Cc: Tejun Heo Cc: Jens Axboe Cc: Johannes Weiner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/filemap.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/mm/filemap.c +++ b/mm/filemap.c @@ -438,7 +438,8 @@ int __filemap_fdatawrite_range(struct ad .range_end = end, }; - if (!mapping_cap_writeback_dirty(mapping)) + if (!mapping_cap_writeback_dirty(mapping) || + !mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) return 0; wbc_attach_fdatawrite_inode(&wbc, mapping->host);