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=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 9EB62C282DA for ; Wed, 17 Apr 2019 21:04:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 626092183E for ; Wed, 17 Apr 2019 21:04:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=web.de header.i=@web.de header.b="YigHpAy3" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729251AbfDQVEg (ORCPT ); Wed, 17 Apr 2019 17:04:36 -0400 Received: from mout.web.de ([212.227.15.4]:43867 "EHLO mout.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728074AbfDQVEg (ORCPT ); Wed, 17 Apr 2019 17:04:36 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=web.de; s=dbaedf251592; t=1555535071; bh=sBRgnhfecbuf82KQZNLyXO3dpBDg24snYH5r9/nq6e8=; h=X-UI-Sender-Class:Subject:To:Cc:References:From:Date:In-Reply-To; b=YigHpAy3YEGM3INSHwyn4rNzg03Jwgu2o0vtweRGKWPUUQDJJvRbijn8GyGutNnES NWm+PsDLoxJHe9KtHpPFKckb8syPNAr8dI9qs9UQGtif8HcKrK3O5q4rR9nN/uJRe5 O934dh2VnO0ha0bi/OB6OwFVQCbEena5GyQd5OlY= X-UI-Sender-Class: c548c8c5-30a9-4db5-a2e7-cb6cb037b8f9 Received: from laptop.manuel.cli.intranet ([109.192.218.194]) by smtp.web.de (mrweb003 [213.165.67.108]) with ESMTPSA (Nemesis) id 0LecN4-1gUu813Y9W-00qS2C; Wed, 17 Apr 2019 23:04:31 +0200 Subject: Re: Adding QCOW2 reading/writing support To: Hannes Reinecke , Ming Lei Cc: linux-block References: <60bbe5e0-317d-8ead-0eb8-d1dc79927bc8@web.de> <2fbeba35-38f3-22cf-a4d5-49f8af5e6802@web.de> <39218225-a402-fb3a-dbc6-db2d95e51bd3@suse.de> From: Manuel Bentele Openpgp: id=5260D26DAE5C7FDF3113C572EC7CB9F864CA371E Autocrypt: addr=manuel-bentele@web.de; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <39218225-a402-fb3a-dbc6-db2d95e51bd3@suse.de> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: de-DE X-Provags-ID: V03:K1:ofEWQpL8jI3mGohZYyuO2YUTqNoTBPOQMQqgwnUtyA/HOq7VWxd qiOl9CgJ/Wf1EmTROhMTKCzw4zdSm5UUmfe3HdJ7aWtjYjZz/yuWax2TlUpX0Ux8GiubrZf QKSJioNW34upVjFoNpBDRO7P+atcqS4WE0jRVIAELHAWIZO3QUjn0DjorlWuENAmfmRD513 kBlqeTrU5KdtPfvaW0BKQ== X-UI-Out-Filterresults: notjunk:1;V03:K0:yH5c/f8eYhM=:KqPbHc2WkUNMxFXflLhzWW AQKL23CpPLIyuOTWuVYGANpu2x4DdYcu4aQ3cD7te3xvOxSH7z7m3kFo7Et5mRxl/qAj/l3qm fBacHrhFO9EPnhQkPSLB+YYVl1M8P/Hf0loAqehVXIz2TfZRpWSi0vKibNq9fkUpvPTCqNDei r6S7T03vC6ohYyIi9VSDykpgME8uG8qz0YHuK6c83Xzjh90lRefyPqSYG572yeZksfVdHPbrT O7KXavHCJt+NaB4aE/KPXjuu+5iH3xokmLUm2WDFRfNZBsP2r3TTbnqO9+J25DFKhTzInQmgW wtTH3wdgDBfwdGvbb7iwLSczTK1vmI7D003IDLhGjc1VOADUKCFjLutktvwKWtiMYQrIcv+JH W6Zu5ZMqzNHY4tZPdXgUuX1UjrHteRt8LcNfK9yg6WKrGVBKKmkgXqGD+O3SFl92BWl9WyxDt W+uSUctA9zPIQi3MAxw1oh/XaxOrJm2a072Qszd78Ix1gyIQsWMiLi9vrpeEaLMW00FIBm2q6 e0VgyYa4AyZmfIkMoFf/PVjUJ897Wp5le6lJlulvDTfqAOmpBXDekUpll8fUwrmeC7WLg2eTJ nHvoc2lhO20+8zh6rYDpVHEXoQRul4Yk2Inkm/Kv7JAm8NWPXkFnJTllGQ9TViAJhJJTh1j7w Uydm4wm5rC50sWLeksiaEX+SvVhEpUZSGjRdt6gxT7OmPCPepr5avJmt6/EwbbV7bqR/d2i5o tVZ+pv6wYG9VjCKLZx/D6Fd98BzdOSOHRywVnEUhVwSEl620tyCgldueqV50d2kPh/Sm94BsI mXY12G3oiuaIfV68UZtn6kj5KwSkJZAxyXm2MWc/b9m/3vMOrpNBtBVO4GJkLA5f2hdJo4rz1 F/1vto+dXcT/kE4uBbn1y4RzdrvO/I5o9Q4VLg7uDDycAxXkeBURaPX7bL+buMrj9syqtIMhN M8qQGp1WdsQ== Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 17.04.19 14:16, Hannes Reinecke wrote: > On 4/17/19 1:32 PM, Manuel Bentele wrote: >> Hi, >> >> On 17.04.19 03:35, Ming Lei wrote: >>> Hi, >>> >>> On Wed, Apr 17, 2019 at 5:33 AM Manuel Bentele >>> wrote: >>>> Hi everyone >>>> >>>> I'm going to implement an in-kernel reading of QCOW2 images. >>>> In the project, I only need the reading of QCOW2 images, but it's >>>> essential to make thoughts for the implementation of the writing, too. >>>> One of the difficulties seems to be the support of making an image >>>> sparse (resizing the disk image). >>> Could you describe this requirement in a bit more detail? Especially >>> why >>> do you want to read/write QCOW2 in kernel? >> >> Yes, of course. The implementation of reading a QCOW2 disk image >> in-kernel is required for an already existing system in the university >> environment. >> At the moment, the Linux kernel, initramfs, etc. for each client in the >> system is loaded via PXE boot and then the block device with the default >> file system is included with the help of a modified nbd version, called >> dnbd (distributed nbd). >> Due to the fact that the data on the default file system is only for non >> persistent one-time provision of a client, read access is sufficient. >> The user related data is stored on a network storage, as mostly done in >> large scale infrastructures. >> >> Now, the goal is to minimize the network usage and avoid nbd. >> Furthermore, fixed configured and packed boot images should be avoided. >> Therefore, the advantage of the sparse and compression functionality of >> QCOW2 should be used. >> A workaround for that problem could be the local usage of nbd to include >> the QCOW2 disk image as block device, but it involves a lot of >> interaction between user and kernel space and thus an decreasing >> performance. That leads to the motivation to implement the reading of >> QCOW2 disk images directly in the kernel and aim for an merge into the >> mainline kernel source to avoid out-of-kernel-tree maintenance. >> >> If you have any questions related to the described use case or if you >> require more information, please let me know. >> Thanks for your help. >> > cramfs? > Or btrfs with compression enabled? > > Cheers, > > Hannes Thanks for your simple idea to choose cramfs or btrfs with compression enabled. I will suggest that as alternative at the next project meeting. Regards, Manuel