From nobody Mon Feb 9 06:49:30 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=1584470003; cv=none; d=zohomail.com; s=zohoarc; b=Mg1O25BLJ1Zr3trVhCxLLwCOPw1CXwAnA/IIjHGyPOhvSJNOW544sv6SbAM+KbAm3ORAvkyITTivyF0baW/wa8fgIKXT0Z0Ig3yprP/QW5b7wJ4+yZ2B1OhXOcTAwC8r0ifuHh/K+K21EpuM13ejNN/XlJDvkGgGJcn0tAVHL2k= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1584470003; 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=jqTKqtd2jDDQ2OjEdrmXgcDY2lStZiVJr05vUx6LPMs=; b=aIidH7tT5Ic8QSzTs3FC0C90JYwBab/+7puUXSlsS4pafK0h5QJPpH0NoDJueeZu4WixblmvJov7C7goH9rz5CBHfK9tmjqe1XBApdpIGhF/Do0VQezsZLAjy4NucnjA2y1XeQIKUSFs7VsJBJXRRMnKjo8s040qosWYKT4P71Q= 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 1584470003577841.9802805622958; Tue, 17 Mar 2020 11:33:23 -0700 (PDT) Received: from localhost ([::1]:39368 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jEH1m-0000HC-EX for importer@patchew.org; Tue, 17 Mar 2020 14:33:22 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:48688) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jEGmt-0003Lc-KX for qemu-devel@nongnu.org; Tue, 17 Mar 2020 14:18:00 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1jEGms-0008UM-Gj for qemu-devel@nongnu.org; Tue, 17 Mar 2020 14:17:59 -0400 Received: from fanzine.igalia.com ([178.60.130.6]:57720) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1jEGms-0005V7-78; Tue, 17 Mar 2020 14:17:58 -0400 Received: from [81.0.35.138] (helo=perseus.local) by fanzine.igalia.com with esmtpsa (Cipher TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim) id 1jEGmD-00014r-39; Tue, 17 Mar 2020 19:17:17 +0100 Received: from berto by perseus.local with local (Exim 4.92) (envelope-from ) id 1jEGlw-0006Or-T2; Tue, 17 Mar 2020 19:17:00 +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=jqTKqtd2jDDQ2OjEdrmXgcDY2lStZiVJr05vUx6LPMs=; b=pyTxDLfavOBARhoSz75na+X1vWd6wRqF+akZVYJHPMU8XVSGbMe3Ut/BHbvg3g2GlXVTBS3rx6p7V2XYGPELHern1ndZ2C68t4hChoqveS4VJeJpku7vNl4pldy3m6hpQjpNClAzuYFVE+S9UQNi5ngbSfCgreZZuTlwoXWYMe+dM6nby3GnEVTJhOsJmzlA2H6Y1mUQhEQuhgibhVpQhLClJZL02Lsx/jRhVHg83aqD4pGghJ0+Xu3jlBWDxnYVuwazmzBmEwrDMdw9lRCE+mhZ4fy9tBYfYZsAqsrcf8DaTd10ewhABrQEuEQjIh/NDi0lbc+3cUoeS0TIFrzMyA==; From: Alberto Garcia To: qemu-devel@nongnu.org Subject: [PATCH v4 25/30] qcow2: Add subcluster support to handle_alloc_space() Date: Tue, 17 Mar 2020 19:16:22 +0100 Message-Id: <7346b6242cb3589cf946314db445edc9250bd3e7.1584468723.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 , 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 Reviewed-by: Vladimir Sementsov-Ogievskiy --- block/qcow2.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/block/qcow2.c b/block/qcow2.c index 88daaf11a0..ad230ed1b1 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -2349,6 +2349,9 @@ 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; @@ -2363,16 +2366,14 @@ 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