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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BD601C25B07 for ; Sat, 6 Aug 2022 14:52:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231938AbiHFOv7 (ORCPT ); Sat, 6 Aug 2022 10:51:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57740 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230211AbiHFOv5 (ORCPT ); Sat, 6 Aug 2022 10:51:57 -0400 Received: from mail-pl1-x62c.google.com (mail-pl1-x62c.google.com [IPv6:2607:f8b0:4864:20::62c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 10FC4101CB for ; Sat, 6 Aug 2022 07:51:55 -0700 (PDT) Received: by mail-pl1-x62c.google.com with SMTP id p8so4952997plq.13 for ; Sat, 06 Aug 2022 07:51:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20210112.gappssmtp.com; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :from:to:cc; bh=ZHZGZq6h+lUo2eCrK9NN33tawRm/nou4eWvVvyVV5/g=; b=IBJCY8eQMmxSsTRzXC8fUR9mMTETadx7Dc7FFAwqZFyNrLd21rO/zwCCeRr3O4SsXU rRPG0BDeoL5+W0aNiX5rhkC+XKA8YS4/LZr5KxNs/6ngYmStUJPywy459UgvTwoTUCq8 K3YDkmWP3h8cTknXLO8Ns0Sc9LPkFzKLyVYxZqRQtXVBBOdEegG5EtUs2PLPAUlPbRZy 5FYEtkqxHT7QPWyUy3n7AsLfsjhjEI6FeqD2b1IUy4RmvjgaXdSnj8Vy/MWW4nJaITNY V3gfPD17xAHYLTAZ/0ihbLyddkJmNk7nChXr9zWbZf8dEOgL04rXZMclXiHMrHn50kB9 8lWQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc; bh=ZHZGZq6h+lUo2eCrK9NN33tawRm/nou4eWvVvyVV5/g=; b=zpL54+KuA0JOiEY3nxgdja5w1o7KfXEoG7ui6lagZapWloTQZ0zbbaVp3FzCT7cRUv SsTS4rjMgEx4EnKuTyjR7Jo+L7TUJOW1Ma07tHzMkcPUWP5NSOEXJtWeGpA/wbficcmA 7oWUsIFaJJ6JxuGjFxDjgmyXgQmmc49+h1NED6PE8n+uu6eNAbo3zGGYu99iFSC9hxUn JqAso7F66o+CWf29PNs572H/gYiqDyZszfFCrI5lRnV5REiNaMEoRZbwz+x50fiRkKlh 9EIcIO9fpXzXbeLOIFe9ekY+gXAAuRD2vLj7Tj8kEOb3TbPdD6uz9UeET4ZQeqb2if3e At4Q== X-Gm-Message-State: ACgBeo1Vxx6iXgzXHlHmmKuxa3wVdM1mXg4lp6+PhpYpZs3takFEUJ+p Uv4+Dnt5DQMloEP9vBxCZLWDag== X-Google-Smtp-Source: AA6agR5tB1lfDWW5CK6g4gZATc2POoUrGVodj3DAFSvqGlbMXd9oczcdSfywNEA6LKlI4avxeOne+w== X-Received: by 2002:a17:902:bd08:b0:16d:4230:cb45 with SMTP id p8-20020a170902bd0800b0016d4230cb45mr11344547pls.59.1659797514464; Sat, 06 Aug 2022 07:51:54 -0700 (PDT) Received: from [192.168.1.100] ([198.8.77.157]) by smtp.gmail.com with ESMTPSA id o187-20020a625ac4000000b0052ef9556f47sm1527411pfb.40.2022.08.06.07.51.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 06 Aug 2022 07:51:53 -0700 (PDT) Message-ID: <026c2c04-aec2-0a8c-ed96-f31ae0918b2e@kernel.dk> Date: Sat, 6 Aug 2022 08:51:52 -0600 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:91.0) Gecko/20100101 Thunderbird/91.10.0 Subject: Re: [PATCH RESEND 1/1] loop: introduce LO_FLAGS_NODEALLOC Content-Language: en-US To: Zhang Boyang , Christoph Hellwig , linux-block@vger.kernel.org Cc: Tetsuo Handa , Jan Kara , Ming Lei , "Darrick J . Wong" , Chaitanya Kulkarni , Damien Le Moal , "Martin K . Petersen" , linux-kernel@vger.kernel.org References: <20220806114943.8754-1-zhangboyang.id@gmail.com> <20220806114943.8754-2-zhangboyang.id@gmail.com> From: Jens Axboe In-Reply-To: <20220806114943.8754-2-zhangboyang.id@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/6/22 5:49 AM, Zhang Boyang wrote: > Previously, for file-backed loop devices, REQ_OP_DISCARD and > REQ_OP_WRITE_ZEROES (without REQ_NOUNMAP) are implemented using > fallocate(FALLOC_FL_PUNCH_HOLE), which will cause the underlying file to > be sparse and disk space freed. The users have no choice to prevent this > this from happening. > > This patch introduces LO_FLAGS_NODEALLOC. With this flag set, > REQ_OP_DISCARD and REQ_OP_WRITE_ZEROES are forced to use > fallocate(FALLOC_FL_ZERO_RANGE). The disk space of underlying file is > kept allocated. This is useful if users, for example, want to use a > preallocated file as the backing file. Just in terms of readability, I would prefer if NO_DEALLOC is used consistently rather than NODEALLOC. The latter reads more like node-alloc to me. -- Jens Axboe