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=-2.5 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, 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 194E4C433DF for ; Wed, 24 Jun 2020 15:00:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E8D55206C0 for ; Wed, 24 Jun 2020 15:00:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="qsvuBeQg" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404060AbgFXPAu (ORCPT ); Wed, 24 Jun 2020 11:00:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55312 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404037AbgFXPAu (ORCPT ); Wed, 24 Jun 2020 11:00:50 -0400 Received: from mail-pj1-x1041.google.com (mail-pj1-x1041.google.com [IPv6:2607:f8b0:4864:20::1041]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AEEACC0613ED for ; Wed, 24 Jun 2020 08:00:49 -0700 (PDT) Received: by mail-pj1-x1041.google.com with SMTP id ne5so1265700pjb.5 for ; Wed, 24 Jun 2020 08:00:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=Q/jaQeCVttGzGBo3E3lk1QjN0UoCwQgqot3lYK2zXtk=; b=qsvuBeQgO4niMQcI2gC+VVoIgpUqo5H4wRPLlaR/5qawyoXdMx/bjxy7jtPw3aL8Dl cRg0StjUcxNFOmQnJunhva1NegHntMT8fa77CMkohiT1LX1ydJgW8uGuDjysJPCp/35R znrly6bkXru8zbZenMv52ZiGlSJ91NS8nCH0gnNyaTgbSN91QAtpFb9Pizp9ez9VUpZR lkCSizcvK1T9hmpEE8ePUTS0LPXCQRR/r7Kz54/FhrDGancf3WJTukegFfSwMmgTEQw7 jqA687/rpGcmCpsu5xlVqxiDBCSFTSyk7tjMNs+8LBV//NZ7jPB012Xm3BxjFW42Ee5C w2jw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=Q/jaQeCVttGzGBo3E3lk1QjN0UoCwQgqot3lYK2zXtk=; b=TRIiTABb9IdizsuW4Q1s4TFjoPnyGv5bVT9cMtk1GWehCJ4rxNpPJD8C3al83Wbu6e E/qUSrrNBuFihLjtDRKsFAyPmpSWWYR+a/oBVpyBrVuTra2CD3FBxYbnuAKBq5RDgxWK j/+uCqlAxIIybAC27bHBpY4Qh8r5Mjh0eVj2rLuPovPvjeAnjozVQRyG4if96HZ+9Oze cw64uMHkYl3DYKgp32vGenJhRl0OU6onizFNp+AbWa5t72mB/nLoIh5I3NnwEg7J6XLP NsqyRVhHcTq0OqTyGdHKUsAkF/9R5NWwEbh4r6q3jVWhSqZRK5kv7b74TtWF/aDsDunB XXyg== X-Gm-Message-State: AOAM530lD+6zuta57uhTLPVuPTJvfEV0TIwHIqxyMpG2gG5JkfErAJ6A /tLH/W+N5xuW8PVjs3lZBuslOsvq1HI= X-Google-Smtp-Source: ABdhPJySN748/btTbadKTHVRipOZVFkvJAeaRPC1DlqdK8kxD+Mddoxrv8JQ5kTFSMXrj12Wq4V18g== X-Received: by 2002:a17:90a:2070:: with SMTP id n103mr29733694pjc.109.1593010849032; Wed, 24 Jun 2020 08:00:49 -0700 (PDT) Received: from [192.168.1.188] ([66.219.217.173]) by smtp.gmail.com with ESMTPSA id m8sm5470354pjk.20.2020.06.24.08.00.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 24 Jun 2020 08:00:48 -0700 (PDT) Subject: Re: [PATCH 05/15] mm: allow read-ahead with IOCB_NOWAIT set To: Matthew Wilcox , Dave Chinner Cc: io-uring@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, Johannes Weiner References: <20200618144355.17324-1-axboe@kernel.dk> <20200618144355.17324-6-axboe@kernel.dk> <20200624010253.GB5369@dread.disaster.area> <20200624014645.GJ21350@casper.infradead.org> From: Jens Axboe Message-ID: Date: Wed, 24 Jun 2020 09:00:46 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20200624014645.GJ21350@casper.infradead.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: io-uring-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 6/23/20 7:46 PM, Matthew Wilcox wrote: > On Wed, Jun 24, 2020 at 11:02:53AM +1000, Dave Chinner wrote: >> On Thu, Jun 18, 2020 at 08:43:45AM -0600, Jens Axboe wrote: >>> The read-ahead shouldn't block, so allow it to be done even if >>> IOCB_NOWAIT is set in the kiocb. >> >> Doesn't think break preadv2(RWF_NOWAIT) semantics for on buffered >> reads? i.e. this can now block on memory allocation for the page >> cache, which is something RWF_NOWAIT IO should not do.... > > Yes. This eventually ends up in page_cache_readahead_unbounded() > which gets its gfp flags from readahead_gfp_mask(mapping). > > I'd be quite happy to add a gfp_t to struct readahead_control. > The other thing I've been looking into for other reasons is adding > a memalloc_nowait_{save,restore}, which would avoid passing down > the gfp_t. That was my first thought, having the memalloc_foo_save/restore for this. I don't think adding a gfp_t to readahead_control is going to be super useful, seems like the kind of thing that should be non-blocking by default. -- Jens Axboe