From patchwork Sat Oct 26 21:25:24 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alberto Garcia X-Patchwork-Id: 11213901 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 40803112C for ; Sat, 26 Oct 2019 22:07:47 +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 1103A2084C for ; Sat, 26 Oct 2019 22:07:47 +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="rbSCc3gr" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1103A2084C 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+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Received: from localhost ([::1]:42948 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iOUDq-00066H-60 for patchwork-qemu-devel@patchwork.kernel.org; Sat, 26 Oct 2019 18:07:46 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:60036) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iOTZj-00005D-GH for qemu-devel@nongnu.org; Sat, 26 Oct 2019 17:26:20 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iOTZi-0005Lv-Ca for qemu-devel@nongnu.org; Sat, 26 Oct 2019 17:26:19 -0400 Received: from fanzine.igalia.com ([178.60.130.6]:42511) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1iOTZg-0005F7-90; Sat, 26 Oct 2019 17:26:16 -0400 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=MR11jBKImXplnlOGrFOr9e3JUvDW+emKlEW8jxCPt6I=; b=rbSCc3grtCbGevTpTIu7A6owan3L9mAngSaluiCYiepqZvXp+5wiZf61O4IbX4PFcJUguips2CBINNPOkEq+c6/mWMpnXr2NAj+xsGXMQGqJNTeijWvjwdlklEjgikGK3pwXfo5tubCjqXu85gmT84zowzPp1yJ9MHRu9BgrUWdKS6m32vnRjzzBJIUuFTJxIzdCBMreRqnH/mJ8zZa6jfOjElXEntZn0TQhFn2BcMFOnM/twwqx0g3QEIHROjjuprWqQr2j+r5p/hQUhqGAIJF3JYw6Pu3qiTWhyK6TnOdNF52PkiX1OG92oWI3X11GmWxRzp6G0VUvnYk/sU6sQg==; Received: from 87-100-137-117.bb.dnainternet.fi ([87.100.137.117] helo=perseus.local) by fanzine.igalia.com with esmtpsa (Cipher TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim) id 1iOTZJ-00046A-9m; Sat, 26 Oct 2019 23:25:53 +0200 Received: from berto by perseus.local with local (Exim 4.92) (envelope-from ) id 1iOTZ1-0001Pj-1E; Sun, 27 Oct 2019 00:25:35 +0300 From: Alberto Garcia To: qemu-devel@nongnu.org Subject: [RFC PATCH v2 22/26] qcow2: Add subcluster support to handle_alloc_space() Date: Sun, 27 Oct 2019 00:25:24 +0300 Message-Id: X-Mailer: git-send-email 2.20.1 In-Reply-To: References: MIME-Version: 1.0 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+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" 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 0261e87709..01322ca449 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -2304,6 +2304,9 @@ static int handle_alloc_space(BlockDriverState *bs, QCowL2Meta *l2meta) for (m = l2meta; m != NULL; m = m->next) { int ret; + uint64_t start_offset = m->alloc_offset + m->cow_start.offset; + uint64_t nb_bytes = m->cow_end.offset + m->cow_end.nb_bytes - + m->cow_start.offset; if (!m->cow_start.nb_bytes && !m->cow_end.nb_bytes) { continue; @@ -2318,16 +2321,14 @@ static int handle_alloc_space(BlockDriverState *bs, QCowL2Meta *l2meta) * efficiently zero out the whole clusters */ - ret = qcow2_pre_write_overlap_check(bs, 0, m->alloc_offset, - m->nb_clusters * s->cluster_size, + ret = qcow2_pre_write_overlap_check(bs, 0, start_offset, nb_bytes, true); if (ret < 0) { return ret; } BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_ALLOC_SPACE); - ret = bdrv_co_pwrite_zeroes(s->data_file, m->alloc_offset, - m->nb_clusters * s->cluster_size, + ret = bdrv_co_pwrite_zeroes(s->data_file, start_offset, nb_bytes, BDRV_REQ_NO_FALLBACK); if (ret < 0) { if (ret != -ENOTSUP && ret != -EAGAIN) {