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=-0.8 required=3.0 tests=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 EF215C3A589 for ; Tue, 20 Aug 2019 12:50:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BBCE522DA9 for ; Tue, 20 Aug 2019 12:50:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729261AbfHTMug convert rfc822-to-8bit (ORCPT ); Tue, 20 Aug 2019 08:50:36 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41278 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728657AbfHTMug (ORCPT ); Tue, 20 Aug 2019 08:50:36 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 29079307C947; Tue, 20 Aug 2019 12:50:36 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-120-255.rdu2.redhat.com [10.10.120.255]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5538510016E9; Tue, 20 Aug 2019 12:50:31 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <20190820115731.bed7gwfygk66nj43@pegasus.maiolino.io> References: <20190820115731.bed7gwfygk66nj43@pegasus.maiolino.io> <20190808082744.31405-1-cmaiolino@redhat.com> <20190808082744.31405-3-cmaiolino@redhat.com> <20190814111535.GC1885@lst.de> To: Carlos Maiolino Cc: dhowells@redhat.com, Christoph Hellwig , linux-fsdevel@vger.kernel.org, adilger@dilger.ca, jaegeuk@kernel.org, darrick.wong@oracle.com, miklos@szeredi.hu, rpeterso@redhat.com, linux-xfs@vger.kernel.org Subject: Re: [PATCH 2/9] cachefiles: drop direct usage of ->bmap method. MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <7002.1566305430.1@warthog.procyon.org.uk> Content-Transfer-Encoding: 8BIT Date: Tue, 20 Aug 2019 13:50:30 +0100 Message-ID: <7003.1566305430@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.46]); Tue, 20 Aug 2019 12:50:36 +0000 (UTC) Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org Carlos Maiolino wrote: > > > + block = page->index; > > > + block <<= shift; > > > > Can't this cause overflows? > > Hmm, I honestly don't know. I did look at the code, and I couldn't really spot > anything concrete. Maybe, though we'd have to support file sizes over 16 Exabytes for that to be a problem. Note that bmap() is *only* used to find out if the page is present in the cache - and even that I'm not actually doing very well, since I really *ought* to check every block in the page. I really want to replace the use of bmap entirely with iov_iter doing DIO. Cachefiles currently does double buffering because it works through the pagecache of the underlying to do actual read or write - and this appears to cause memory management problems. David