From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f196.google.com ([209.85.223.196]:39638 "EHLO mail-io0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932718AbeFUNwD (ORCPT ); Thu, 21 Jun 2018 09:52:03 -0400 Received: by mail-io0-f196.google.com with SMTP id f1-v6so3044102ioh.6 for ; Thu, 21 Jun 2018 06:52:03 -0700 (PDT) Subject: Re: [PATCHSET v3 0/4] Submit ->readpages() IO as read-ahead To: Christoph Hellwig Cc: Andrew Morton , linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk References: <1527691329-2371-1-git-send-email-axboe@kernel.dk> <20180619165640.0c36473a33e20ea6c0fda463@linux-foundation.org> <9b1d2225-104d-865f-d821-8670271d6d4a@kernel.dk> <20180620125801.6e563efc5ed6af2f12c27f07@linux-foundation.org> <20180621122116.GA14053@infradead.org> From: Jens Axboe Message-ID: Date: Thu, 21 Jun 2018 07:52:00 -0600 MIME-Version: 1.0 In-Reply-To: <20180621122116.GA14053@infradead.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On 6/21/18 6:21 AM, Christoph Hellwig wrote: > On Wed, Jun 20, 2018 at 04:28:54PM -0600, Jens Axboe wrote: >> The assumption has been true for a decade or more. The only problem with >> it is that we have this ->readpages() interface that is only used for >> readahead. Hence it should be ->readahead() or similar, that avoid the >> fragility argument. > > Or just stop this whole bike shed. ->readpages doesn't keep the pages > it reads locked, so it fundamentally is a readahead style operation. > > Now if we actually want do to anything with that information is another > question that I already asked in reply to the first round of these > patches. > > Especially as e.g. nvme actually sets hints based on the flag, that > if hardware actually ever looked at them might be doing the wrong > thing (fortunately for us I doubt any nvme hardware actually looks > at that flag). In most of these cases, these types of hints don't translate uniformly across devices. So whether we pass them on to the actual hardware or not is a different matter. For now, as mentioned, all I care about is getting the tracing working properly, and being able to functionally differentiate between a read and a read-ahead read in the block layer. -- Jens Axboe