From nobody Mon Feb 9 04:45:24 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zohomail.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 (zohomail.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=1577015269; cv=none; d=zohomail.com; s=zohoarc; b=DGtccyySsCyX/CQNqC4cokqikg8KXfIUOQbIkzOJCh9MQk3ZYJDMKsD+TY+0seziszHqWlYo4FY9XciQ/TVAY4qIXwez2BxDQecgOlN38zJWR8l0bG1U1JJn9U/ovmcaEYpB9//U1sEt8WCbsShrgcqEhl4lEsCySYOivWcaXnA= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1577015269; 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=/cY/IXpXQHwL/+wBuvEvO5IwS2Zd6P6ebh+NCvUlByc=; b=nXhshn9iuU52K341QmeJj2I6lPeEHytW9XJn+ufRngg5Etd6Eu4GnL88FC2JbiFfK45fhYbZYyUAnmt+rKQYAhMIfvEtAwBBS264FK8GEVOUSHzpeN+6fM/H/f4lPNWSeo9Sjgwbb64i/zXXB39kgG8A5MDUEpOsuNKjsPgxDc4= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=fail; spf=pass (zohomail.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 1577015269048360.29152171605733; Sun, 22 Dec 2019 03:47:49 -0800 (PST) Received: from localhost ([::1]:46770 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iizi7-000537-De for importer@patchew.org; Sun, 22 Dec 2019 06:47:47 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:44178) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iizZD-0003U3-Pl for qemu-devel@nongnu.org; Sun, 22 Dec 2019 06:38:36 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iizZB-00073x-TJ for qemu-devel@nongnu.org; Sun, 22 Dec 2019 06:38:35 -0500 Received: from fanzine.igalia.com ([178.60.130.6]:35040) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1iizZB-0004nX-IB; Sun, 22 Dec 2019 06:38:33 -0500 Received: from [80.30.182.172] (helo=perseus.local) by fanzine.igalia.com with esmtpsa (Cipher TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim) id 1iizYV-0005dP-0q; Sun, 22 Dec 2019 12:37:52 +0100 Received: from berto by perseus.local with local (Exim 4.92) (envelope-from ) id 1iizXu-0001WG-Tq; Sun, 22 Dec 2019 12:37:14 +0100 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=/cY/IXpXQHwL/+wBuvEvO5IwS2Zd6P6ebh+NCvUlByc=; b=nInR2eav65cccb7txeHu+JY1E2y6se1NWXkiWJmi8+SkeNPe2SU0pKW3eFw0a9dOkE6bRaBwDZL6LyizczeiC6Fqi5304RpITHxR2SCcFH/a2rarKfTWi/nK5ugAzlDyPPyK6RKxpbQmwUcUwDh+kkl2KLUWZOuZBPw9aEmlI7azOVgl+ugSJZ8GPJg5l4dLlAMYm9nFe+5N/lz0i49wV3+gw7gwWxcLHyiuSYLB32kmhihxeyFG/mVX2syyB4qG/QHhsmjP4P0Hpil1vKBAX/lMxBuHGpQ1u0/+FEG0OPIIoutFnKbNrlpANv+WgCJZsiHMCOm3L69WCJBxVU18MQ==; From: Alberto Garcia To: qemu-devel@nongnu.org Subject: [RFC PATCH v3 23/27] qcow2: Add subcluster support to handle_alloc_space() Date: Sun, 22 Dec 2019 12:37:04 +0100 Message-Id: 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 , Vladimir Sementsov-Ogievskiy , "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 Reviewed-by: Max Reitz --- block/qcow2.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/block/qcow2.c b/block/qcow2.c index 1d3da0ccf6..242001afa2 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -2354,6 +2354,9 @@ 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; + unsigned 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; @@ -2368,16 +2371,14 @@ 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