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,URIBL_BLOCKED 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 C995AC3A5A6 for ; Sat, 31 Aug 2019 00:46:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9AC2223717 for ; Sat, 31 Aug 2019 00:46:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728358AbfHaAqC (ORCPT ); Fri, 30 Aug 2019 20:46:02 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37214 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728279AbfHaAqC (ORCPT ); Fri, 30 Aug 2019 20:46:02 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 816D2308404E; Sat, 31 Aug 2019 00:46:02 +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 EF4A860BF7; Sat, 31 Aug 2019 00:45:57 +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: <20190830165920.GA28182@lst.de> References: <20190830165920.GA28182@lst.de> <20190829071312.GE11909@lst.de> <20190820115731.bed7gwfygk66nj43@pegasus.maiolino.io> <20190808082744.31405-1-cmaiolino@redhat.com> <20190808082744.31405-3-cmaiolino@redhat.com> <20190814111535.GC1885@lst.de> <7003.1566305430@warthog.procyon.org.uk> <2587.1567181871@warthog.procyon.org.uk> To: Christoph Hellwig Cc: dhowells@redhat.com, Carlos Maiolino , 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: <28401.1567212357.1@warthog.procyon.org.uk> Date: Sat, 31 Aug 2019 01:45:57 +0100 Message-ID: <28402.1567212357@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.40]); Sat, 31 Aug 2019 00:46:02 +0000 (UTC) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Christoph Hellwig wrote: > We'll you'd need to implement a IOCB_NOHOLE, but that wouldn't be all > that hard. Having a READ_PLUS like interface that actually tells you > how large the hole is might be hard. Actually, that raises another couple of questions: (1) Is a filesystem allowed to join up two disjoint blocks of data with a block of zeros to make a single extent? If this happens, I'll see the inserted block of zeros to be valid data. (2) Is a filesystem allowed to punch out a block of valid zero data to make a hole? This would cause me to refetch the data. David