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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 11640C2D0DB for ; Mon, 20 Jan 2020 11:42:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E26EE207E0 for ; Mon, 20 Jan 2020 11:42:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726589AbgATLmP (ORCPT ); Mon, 20 Jan 2020 06:42:15 -0500 Received: from mx2.suse.de ([195.135.220.15]:56526 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726573AbgATLmP (ORCPT ); Mon, 20 Jan 2020 06:42:15 -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 372D1AD5C; Mon, 20 Jan 2020 11:42:13 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 5CD301E0CF1; Mon, 20 Jan 2020 12:42:07 +0100 (CET) Date: Mon, 20 Jan 2020 12:42:07 +0100 From: Jan Kara To: "yukuai (C)" Cc: Jan Kara , hch@infradead.org, darrick.wong@oracle.com, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, houtao1@huawei.com, zhengbin13@huawei.com, yi.zhang@huawei.com Subject: Re: [RFC] iomap: fix race between readahead and direct write Message-ID: <20200120114207.GE19861@quack2.suse.cz> References: <20200116063601.39201-1-yukuai3@huawei.com> <20200116153206.GF8446@quack2.suse.cz> <20200117110536.GE17141@quack2.suse.cz> <976d09e1-e3b5-a6a6-d159-9bdac3a7dc84@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <976d09e1-e3b5-a6a6-d159-9bdac3a7dc84@huawei.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Sun 19-01-20 09:17:00, yukuai (C) wrote: > > > On 2020/1/17 19:05, Jan Kara wrote: > > provide > > allocation for each page separately > > Thank you for your response! > > I do understand there will be additional CPU overhead. But page is allocated > in __do_page_cache_readahead(), which is called before > iomap_begin(). And I did not change that. Sorry, I didn't express myself clearly. In "...one of the big points of iomap infrastructure is that you call filesystem once to give you large extent instead of calling it to provide allocation for each page separately." I meant that with your patch, you call into filesystem to provide "block allocation information" for each page separately. And it seems we both agree this is going to cause additional CPU usage in the common case to improve mostly unsupported corner case. Honza -- Jan Kara SUSE Labs, CR