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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 2BA2AC388F9 for ; Thu, 22 Oct 2020 14:10:46 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5A44B24197 for ; Thu, 22 Oct 2020 14:10:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="h56hKfQH" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5A44B24197 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 6C9FE6B0073; Thu, 22 Oct 2020 10:10:44 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 67BB66B0074; Thu, 22 Oct 2020 10:10:44 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5B93C6B0075; Thu, 22 Oct 2020 10:10:44 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0079.hostedemail.com [216.40.44.79]) by kanga.kvack.org (Postfix) with ESMTP id 2FA506B0073 for ; Thu, 22 Oct 2020 10:10:44 -0400 (EDT) Received: from smtpin21.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id C8081181AEF00 for ; Thu, 22 Oct 2020 14:10:43 +0000 (UTC) X-FDA: 77399747166.21.screw20_32102d627251 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin21.hostedemail.com (Postfix) with ESMTP id A7016180442C2 for ; Thu, 22 Oct 2020 14:10:43 +0000 (UTC) X-HE-Tag: screw20_32102d627251 X-Filterd-Recvd-Size: 2176 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf36.hostedemail.com (Postfix) with ESMTP for ; Thu, 22 Oct 2020 14:10:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=t2bZnP+rctmVrRIc/SzGwMkVhSC+/cbQBfFQMrZXn/8=; b=h56hKfQHD5DGej7Qcr/ErVsAWP m0ffk6kNO0c9y4cnmFK5nLUcTeVFz9+B6jrf/AM6so7t+U1W3DNBq5yUeus1c9gYXhFJD8/qNijjr OF/1TUlZt2xM/+XwEN/FrZiszwdYdmGR+5NIvfg5lpujI4ls9kekj6LrlGF17Q4pFRQR8fpqtS1L8 8k8WIMpcdkXEjqffKw17+HtpYCns4fhto5wLq/BBkUJILWiYYRNQO4t2x92uTLEWt937mP9xHi3Cb zJUZRj6cV35M8MsU4XZKnJ8ZhuDBRRWUWE0ETJpBiHxiB2cbOxgcfmTwcPyZbc4qMW8ppNuVq+wNH pfCTOGOg==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kVbIb-00027y-6o; Thu, 22 Oct 2020 14:10:37 +0000 Date: Thu, 22 Oct 2020 15:10:37 +0100 From: Matthew Wilcox To: Hao Xu Cc: Jens Axboe , io-uring@vger.kernel.org, linux-mm@kvack.org, Johannes Weiner , Andrew Morton Subject: Re: [PATCH RFC] mm: fix the sync buffered read to the old way Message-ID: <20201022141037.GS20115@casper.infradead.org> References: <1603375114-58419-1-git-send-email-haoxu@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1603375114-58419-1-git-send-email-haoxu@linux.alibaba.com> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Oct 22, 2020 at 09:58:34PM +0800, Hao Xu wrote: > The commit 324bcf54c449 changed the code path of async buffered reads > to go with the page_cache_sync_readahead() way when readahead is > disabled, meanwhile the sync buffered reads are forced to do IO in the > above way as well, which makes it go to a more complex code path. But ->readpage is (increasingly) synchronous while readahead should be used to start async I/Os. I'm pretty sure Jens meant to do exactly what he did.