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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 B46A1C433E0 for ; Fri, 29 May 2020 16:07:58 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7F6A72072D for ; Fri, 29 May 2020 16:07:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=igalia.com header.i=@igalia.com header.b="mIr3iP7S" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7F6A72072D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=igalia.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:42506 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jehY5-0005G0-NG for qemu-devel@archiver.kernel.org; Fri, 29 May 2020 12:07:57 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:54482) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jehWx-0004b4-7L; Fri, 29 May 2020 12:06:47 -0400 Received: from fanzine.igalia.com ([178.60.130.6]:50919) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1jehWv-0008TW-2f; Fri, 29 May 2020 12:06:46 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Type:MIME-Version:Message-ID:Date:References:In-Reply-To:Subject:Cc:To:From; bh=WvvQCIvwekoS/kY4NSTaXzv4TT6EdBEo6/pD/7vfBD8=; b=mIr3iP7SR66K1U9KJth9CrgFQfZV4npLVjjC1Q05vy6NS3V6WqoEksktdXzWJeI1x0t5uxuxJ8KlvSHWWowlhqv+ebDVu0aMKR7ktTJVKETf+yffdgobUWv79dclVkd+cuhbYtgRf7ZKMQbGsKcmxbTvJcVwaU0U0rmm9pa8ajDe5k9PIejgc+GeVa3toRnEUxSyKzRBBoGDGchFn9kQumNhO22MoZz3Vxpi2cZw6S1yMIgu9M4VatjBV2likf/aSxGrts6AeTvFDKjumlgrMvlVqg0K9FcY+/cygONvcD21cJhnzPNoS3qYpEb7aSH+3GZW6Y34nUBrDO7AKEMPZA==; Received: from maestria.local.igalia.com ([192.168.10.14] helo=mail.igalia.com) by fanzine.igalia.com with esmtps (Cipher TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim) id 1jehWq-0006l6-BM; Fri, 29 May 2020 18:06:40 +0200 Received: from berto by mail.igalia.com with local (Exim) id 1jehWq-0004kk-2L; Fri, 29 May 2020 18:06:40 +0200 From: Alberto Garcia To: Eric Blake , qemu-devel@nongnu.org Subject: Re: [PATCH v7 28/32] qcow2: Add subcluster support to qcow2_co_pwrite_zeroes() In-Reply-To: <0adafac6-15e8-96eb-6c3f-bb9c182fb2d1@redhat.com> References: <467e4184-2cee-a9e9-9cf0-ee6050ea4319@redhat.com> <0adafac6-15e8-96eb-6c3f-bb9c182fb2d1@redhat.com> User-Agent: Notmuch/0.18.2 (http://notmuchmail.org) Emacs/24.4.1 (i586-pc-linux-gnu) Date: Fri, 29 May 2020 18:06:40 +0200 Message-ID: MIME-Version: 1.0 Content-Type: text/plain Received-SPF: pass client-ip=178.60.130.6; envelope-from=berto@igalia.com; helo=fanzine.igalia.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/29 11:07:06 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x (no timestamps) [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Derek Su , Vladimir Sementsov-Ogievskiy , qemu-block@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu 28 May 2020 09:11:07 PM CEST, Eric Blake wrote: >> I think the problem also exists in the current code (without my >> patches). If you zeroize 10 clusters and the last one is compressed >> you have to repeat the request after having zeroized 9 clusters. > > Hmm. In the pre-patch code, qcow2_co_pwrite_zeroes() calls > qcow2_cluster_zeroize() which can fail with -ENOTSUP up front, but not > after the fact. Once it starts the while loop over clusters, its use > of zero_in_l2_slice() handles compressed clusters just fine; You're right, complete compressed clusters can always be handled, the problem is just when there's subclusters. > But isn't this something we could solve recursively? Instead of > returning -ENOTSUP, we could have zero_in_l2_slice() call > bdrv_pwrite_zeroes() on the (sub-)clusters associated with a > compressed cluster. I suppose we could, as long as BDRV_REQ_NO_FALLBACK is not used. Berto