From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BD1AEC54FCB for ; Fri, 24 Apr 2020 19:40:24 +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 8532D21569 for ; Fri, 24 Apr 2020 19:40:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="brMnYuJW" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8532D21569 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:50742 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jS4BT-0002uf-Jv for qemu-devel@archiver.kernel.org; Fri, 24 Apr 2020 15:40:23 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:57212) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jS4An-0002EY-Gn for qemu-devel@nongnu.org; Fri, 24 Apr 2020 15:39:41 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.90_1) (envelope-from ) id 1jS4Ai-0008EJ-OC for qemu-devel@nongnu.org; Fri, 24 Apr 2020 15:39:41 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:32588 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jS4Ai-00082M-7v for qemu-devel@nongnu.org; Fri, 24 Apr 2020 15:39:36 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1587757174; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=g6AQ+DvP0Ry1hyj2KXj08/u5Fuvqf5Fn5tw16bVmQHk=; b=brMnYuJWBy1Wvd/fuYgNoWuRsmPaWEjgWaycn9SolS1PMNCX+CtrjDsGyWJKfqiC9qJF5h JTuhNmsHyoNWwrKkQwmkaA7eEN7fDkBcdWwNPUfRHl5HqdBKkers+rwjS6NM2NUKCpvwXV Rd5O5w6eMDZKrk2oPJKuvzv9D4ejS54= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-495-U7i8sIqAPhKrCb48fwb9SQ-1; Fri, 24 Apr 2020 15:39:29 -0400 X-MC-Unique: U7i8sIqAPhKrCb48fwb9SQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id AF78D1005510; Fri, 24 Apr 2020 19:39:27 +0000 (UTC) Received: from [10.10.116.80] (ovpn-116-80.rdu2.redhat.com [10.10.116.80]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 47E9E5C1D4; Fri, 24 Apr 2020 19:39:26 +0000 (UTC) Subject: Re: [PATCH v4 23/30] qcow2: Update L2 bitmap in qcow2_alloc_cluster_link_l2() To: Alberto Garcia , qemu-devel@nongnu.org References: <6ffd3ee7ca1e53272705ad34d2ea7ac10b50ade0.1584468723.git.berto@igalia.com> From: Eric Blake Organization: Red Hat, Inc. Message-ID: <15b848ef-3e86-91f4-4ef6-5adde7ac750d@redhat.com> Date: Fri, 24 Apr 2020 14:39:25 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <6ffd3ee7ca1e53272705ad34d2ea7ac10b50ade0.1584468723.git.berto@igalia.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=207.211.31.120; envelope-from=eblake@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/04/24 13:45:11 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 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 , qemu-block@nongnu.org, Max Reitz , Vladimir Sementsov-Ogievskiy , "Denis V . Lunev" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 3/17/20 1:16 PM, Alberto Garcia wrote: > The L2 bitmap needs to be updated after each write to indicate what > new subclusters are now allocated. > > This needs to happen even if the cluster was already allocated and the > L2 entry was otherwise valid. > > Signed-off-by: Alberto Garcia > Reviewed-by: Max Reitz > --- > block/qcow2-cluster.c | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c > index ceacd91ea3..dfd8b66958 100644 > --- a/block/qcow2-cluster.c > +++ b/block/qcow2-cluster.c > @@ -1006,6 +1006,23 @@ int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m) > assert((offset & L2E_OFFSET_MASK) == offset); > > set_l2_entry(s, l2_slice, l2_index + i, offset | QCOW_OFLAG_COPIED); > + > + /* Update bitmap with the subclusters that were just written */ > + if (has_subclusters(s)) { > + unsigned written_from = m->cow_start.offset; > + unsigned written_to = m->cow_end.offset + m->cow_end.nb_bytes ?: > + m->nb_clusters << s->cluster_bits; > + uint64_t l2_bitmap = get_l2_bitmap(s, l2_slice, l2_index + i); > + int sc; > + for (sc = 0; sc < s->subclusters_per_cluster; sc++) { > + int sc_off = i * s->cluster_size + sc * s->subcluster_size; > + if (sc_off >= written_from && sc_off < written_to) { > + l2_bitmap |= QCOW_OFLAG_SUB_ALLOC(sc); > + l2_bitmap &= ~QCOW_OFLAG_SUB_ZERO(sc); > + } > + } Are there more efficient ways to set this series of bits than iterating one bit at a time, while still remaining legible? For example, what if we had something like: l2_bitmap = get_l2_bitmap(...); int sc_from = OFFSET_TO_SC(written_from); int sc_to = OFFSET_TO_SC(written_to - 1); l2_bitmap |= QCOW_OFLAG_SUB_ALLOC_RANGE(sc_from, sc_to); l2_bitmap &= ~QCOW_OFLAG_SUB_ZERO_RANGE(sc_from, sc_to); which would require macros: #define OFFSET_TO_SC(offset) (offset >> (s->cluster_bits - 6)) #define QCOW_OFLAG_SUB_ALLOC_RANGE(from, to) \ deposit64(0, (from), (len) - (from), -1) #define QCOW_OFLAG_SUB_ZERO_RANGE(from, to) \ deposit64(0, (from) + 32, (len) - (from) + 32, -1) > + set_l2_bitmap(s, l2_slice, l2_index + i, l2_bitmap); I'm hoping this function doesn't cause redundant I/O if the L2 entry didn't actually change. But that's not the concern for this patch. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org