From patchwork Sun Dec 22 11:37:04 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alberto Garcia X-Patchwork-Id: 11307381 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 41C1313A4 for ; Sun, 22 Dec 2019 11:46:39 +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 17AEB20665 for ; Sun, 22 Dec 2019 11:46:39 +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="nInR2eav" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 17AEB20665 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]:46770 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iizgz-000537-Mw for patchwork-qemu-devel@patchwork.kernel.org; Sun, 22 Dec 2019 06:46:37 -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 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==; 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 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 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 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, QCowL2Meta *l2meta) for (m = l2meta; m != NULL; m = m->next) { int ret; + uint64_t start_offset = m->alloc_offset + m->cow_start.offset; + unsigned 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; @@ -2368,16 +2371,14 @@ 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) {