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 BD9A6C10F14 for ; Wed, 17 Apr 2019 01:36:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 83F1520821 for ; Wed, 17 Apr 2019 01:36:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="aDCyKxAf" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728856AbfDQBf7 (ORCPT ); Tue, 16 Apr 2019 21:35:59 -0400 Received: from mail-wr1-f67.google.com ([209.85.221.67]:45861 "EHLO mail-wr1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728486AbfDQBf7 (ORCPT ); Tue, 16 Apr 2019 21:35:59 -0400 Received: by mail-wr1-f67.google.com with SMTP id s15so29581374wra.12 for ; Tue, 16 Apr 2019 18:35:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=Hk8oBh8IR2y1WgQpK7lqPC2YhZQ2mFQ1h6PxsNn/E54=; b=aDCyKxAfjAdCY61m5GPhcFYL+310hfsl80aEE/y/V+1u1yzQOzCAKbvGV2/JlYrhAU qgAoHMPCXx4lTOeSDHXUt1ze1YWjs72lAEK+K4OqNJ20yyi1W/CZYF/2Ob50N+AfAJf7 LiIKjUXFmc7B93oRRs1jsRUWgGPs3bOP5jL2AO6u2gZPPoMJLK3KdbfZEFxMDoS3zOcl LvrbAhUshQOoOV5GG2owyTHVivRTDdtVR3U1dqaJYZ6YRXhshYJbOKjBdbehd2SV6lYC A2YfpFm8GAh5zFcv2aZgiHXxllX0VSGkYIsd9qnTCBtoMhItmoy6zzyV5g39kQ7FrVny Qokg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Hk8oBh8IR2y1WgQpK7lqPC2YhZQ2mFQ1h6PxsNn/E54=; b=stH0EXW7Qouuq1ivDYusKFnwydyKwaPDfQZNryP1WDwuWGzeXAAGYQCwYKTGYqmBTF yDThtaZ1E5EYbIpxZpTcEiNjmb25cxRs0bFdPdE1uwZNXos8NWdRXNODm5izFB0tIkuf oIG20EwceVIJfZehO310R3d4Ha1dSzd08VWONgBCnuseA3dBL1Iz7fatQ80s54EYq6Ur G0dj2DiBc3k+2LnSGkU2MntzmquezyujZkJ1FomVWp84T6y9rS3AYh71pqo0O1gfBKv5 JWsOPnvREJJvktR5xuRrlM6gJT1BAdkkaSPZw6EupTRLhclZR4IR9K3lMi/MN8ueKxMt DLpQ== X-Gm-Message-State: APjAAAVEXsPyjqDyO3f1qKjz7A32s744gq5lpK/wkHj37iIeHAQU2C0O kp8lWDO44M8QIWNVeEEXpKB4szC029CBlGnIJHI= X-Google-Smtp-Source: APXvYqwjYuo7KncMCWppQSnGGIL675Yo8fH180HWZvVQfAERE6bo0GVdwj0LjjXhAc/1RZpxS/gdAR4qrLCZ9sWL3eA= X-Received: by 2002:adf:ef0c:: with SMTP id e12mr53134912wro.170.1555464958068; Tue, 16 Apr 2019 18:35:58 -0700 (PDT) MIME-Version: 1.0 References: <60bbe5e0-317d-8ead-0eb8-d1dc79927bc8@web.de> In-Reply-To: <60bbe5e0-317d-8ead-0eb8-d1dc79927bc8@web.de> From: Ming Lei Date: Wed, 17 Apr 2019 09:35:46 +0800 Message-ID: Subject: Re: Adding QCOW2 reading/writing support To: Manuel Bentele Cc: linux-block Content-Type: text/plain; charset="UTF-8" Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org 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? > > Now, I want to ask you for advice: What is the best approach to achieve > this? > > * Implement the reading/writing in the device mapper? > * Extend the loop device? > * Create a new subsystem for the processing of sparse devices or images? > > Or do you have any other idea? The 1st idea is that if this feature is really good requirement. Thanks, Ming Lei