From nobody Mon Feb 9 02:15:24 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; dkim=fail; spf=pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org ARC-Seal: i=1; a=rsa-sha256; t=1571154468; cv=none; d=zoho.com; s=zohoarc; b=agxwvlOEwkSH/PLUDEPOfEADzv4Qq1z3NcZL7z0ew6Q7YcWxUTvfF0JW2KfpUw6FPJ26Vc3rkJDc/ut8nbyCMRKSywyFEJSjXicgQaRnQ755ukdAiufaCLEV3kmWumyjJiwWojyla0HDwFuHAEp2Oi6q604QP9MCOH18GUlRhI8= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zoho.com; s=zohoarc; t=1571154468; h=Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To; bh=noSUEGZeNw8217mG2J5pHPHq6mQwE2+cTlviu1AduTY=; b=N1p/vluLKIWfm6cgSDQr9lIl1y4XRb7KfCtiKQkwsoV0oyZCXOw++PwfQBiT6OTO7ruhOx2mOcLwb3TyOvmokKktAjc6qQvIsm0cgnrXv3C+VHLGF70t6eqRaabtW+WBFAaRux9dNpWaEa4pTwjyULzt+Wrw4T4mYar25ulZwVQ= ARC-Authentication-Results: i=1; mx.zoho.com; dkim=fail; spf=pass (zoho.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1571154468595388.3647782262832; Tue, 15 Oct 2019 08:47:48 -0700 (PDT) Received: from localhost ([::1]:49322 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iKP32-0004Aq-T6 for importer@patchew.org; Tue, 15 Oct 2019 11:47:44 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:48501) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iKOhL-0003MK-L4 for qemu-devel@nongnu.org; Tue, 15 Oct 2019 11:25:20 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iKOhK-0003sJ-4n for qemu-devel@nongnu.org; Tue, 15 Oct 2019 11:25:19 -0400 Received: from fanzine.igalia.com ([178.60.130.6]:47184) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1iKOhJ-0003cJ-HV; Tue, 15 Oct 2019 11:25:17 -0400 Received: from 82-181-115-92.bb.dnainternet.fi ([82.181.115.92] helo=perseus.local) by fanzine.igalia.com with esmtpsa (Cipher TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim) id 1iKOge-0003ai-5h; Tue, 15 Oct 2019 17:24:36 +0200 Received: from berto by perseus.local with local (Exim 4.92) (envelope-from ) id 1iKOfn-00061z-5A; Tue, 15 Oct 2019 18:23:43 +0300 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Transfer-Encoding:MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From; bh=noSUEGZeNw8217mG2J5pHPHq6mQwE2+cTlviu1AduTY=; b=IbXVAIORUqWRfVRMjda2CpGohsz/mkZb217fALgCqTuRj12QIK9VMlJ6a7btEUkID8bUmsVbSfIdWpCvLhMUWTRSgdSEh7QO7gvNhRMIN9/Gyv3TFCI+Q3SDLtoqEh+Q4sw57jVIgF07iDYV3yCP5prN2Ds0MJv/oFYpSrwK2ampN5O9CyUqDLi9oPHdwKZGybZQvm7+9KLp8HYKPQDXaLD1avWz05vuluMHodWFspmC06znX8MgmWHWQPJoI6gt5CNPPbi93UjjX9BVWzqtBO32buFrU1xlv5Qfmbzcq/bTPe1lylX3yszmSWf6AUNRUA3jZnGUuDH07vS06Bo19Q==; From: Alberto Garcia To: qemu-devel@nongnu.org Subject: [RFC PATCH 21/23] qcow2: Add subcluster support to handle_alloc_space() Date: Tue, 15 Oct 2019 18:23:32 +0300 Message-Id: <0645d1ee1f3a0cecb66c5fdde1c4fe1704bf40b1.1571152571.git.berto@igalia.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x (no timestamps) [generic] [fuzzy] X-Received-From: 178.60.130.6 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 , Anton Nefedov , Alberto Garcia , qemu-block@nongnu.org, Max Reitz , "Denis V . Lunev" Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) Content-Type: text/plain; charset="utf-8" The bdrv_co_pwrite_zeroes() call here fills complete clusters with zeroes, but it can happen that some subclusters are not part of the write request or the copy-on-write. This patch makes sure that only the affected subclusters are overwritten. A potential improvement would be to also fill with zeroes the other subclusters if we can guarantee that we are not overwriting existing data. However this would waste more disk space, so we should first evaluate if it's really worth doing. Signed-off-by: Alberto Garcia --- block/qcow2.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/block/qcow2.c b/block/qcow2.c index c222cd261d..c54278ab0b 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -2194,6 +2194,9 @@ static int handle_alloc_space(BlockDriverState *bs, Q= CowL2Meta *l2meta) =20 for (m =3D l2meta; m !=3D NULL; m =3D m->next) { int ret; + uint64_t start_offset =3D m->alloc_offset + m->cow_start.offset; + uint64_t nb_bytes =3D m->cow_end.offset + m->cow_end.nb_bytes - + m->cow_start.offset; =20 if (!m->cow_start.nb_bytes && !m->cow_end.nb_bytes) { continue; @@ -2208,16 +2211,14 @@ static int handle_alloc_space(BlockDriverState *bs,= QCowL2Meta *l2meta) * efficiently zero out the whole clusters */ =20 - ret =3D qcow2_pre_write_overlap_check(bs, 0, m->alloc_offset, - m->nb_clusters * s->cluster_si= ze, + ret =3D qcow2_pre_write_overlap_check(bs, 0, start_offset, nb_byte= s, true); if (ret < 0) { return ret; } =20 BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_ALLOC_SPACE); - ret =3D bdrv_co_pwrite_zeroes(s->data_file, m->alloc_offset, - m->nb_clusters * s->cluster_size, + ret =3D bdrv_co_pwrite_zeroes(s->data_file, start_offset, nb_bytes, BDRV_REQ_NO_FALLBACK); if (ret < 0) { if (ret !=3D -ENOTSUP && ret !=3D -EAGAIN) { --=20 2.20.1