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=-6.5 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 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 35FCBC34026 for ; Tue, 18 Feb 2020 10:39:52 +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 01C9A2173E for ; Tue, 18 Feb 2020 10:39:52 +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="VgXQg1/B" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 01C9A2173E 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]:60630 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j40IB-0002P7-2a for qemu-devel@archiver.kernel.org; Tue, 18 Feb 2020 05:39:51 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:52187) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j40Dv-0001hP-KD for qemu-devel@nongnu.org; Tue, 18 Feb 2020 05:35:28 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1j40Du-0007R8-BL for qemu-devel@nongnu.org; Tue, 18 Feb 2020 05:35:27 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:40393 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1j40Du-0007Qk-6c for qemu-devel@nongnu.org; Tue, 18 Feb 2020 05:35:26 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1582022125; 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=9aPVtQzc7vjGemDWS1kpzm+7k6kudt5hwR47rSwH8tM=; b=VgXQg1/Bt2oVYfgkHjnypFThHJfUwc3Cg/DZdlxZbNLN+RfBdd6LIsiicgQ0V/fHoBP9Tf EG6kOUYia4pBg8Y4K6CXTBmv0+TPFOiZkPY/qZr7UPkRR5iV2KKjGKT3Eaq3e1VJv7+8ao u+O9OssdLs5IbwR8iA10PeA/K8RitvQ= 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-104-dJ2bKjQKMgyGbJbaCEmcVQ-1; Tue, 18 Feb 2020 05:35:22 -0500 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 01F9413FB; Tue, 18 Feb 2020 10:35:21 +0000 (UTC) Received: from localhost (unknown [10.36.118.17]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6877D384; Tue, 18 Feb 2020 10:35:20 +0000 (UTC) From: Max Reitz To: qemu-block@nongnu.org Subject: [PATCH v4 08/19] quorum: Implement .bdrv_recurse_can_replace() Date: Tue, 18 Feb 2020 11:34:43 +0100 Message-Id: <20200218103454.296704-9-mreitz@redhat.com> In-Reply-To: <20200218103454.296704-1-mreitz@redhat.com> References: <20200218103454.296704-1-mreitz@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-MC-Unique: dJ2bKjQKMgyGbJbaCEmcVQ-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.120 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 , Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org, Max Reitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Signed-off-by: Max Reitz --- block/quorum.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) diff --git a/block/quorum.c b/block/quorum.c index 17b439056f..3ece6e4382 100644 --- a/block/quorum.c +++ b/block/quorum.c @@ -813,6 +813,59 @@ static bool quorum_recurse_is_first_non_filter(BlockDr= iverState *bs, return false; } =20 +static bool quorum_recurse_can_replace(BlockDriverState *bs, + BlockDriverState *to_replace) +{ + BDRVQuorumState *s =3D bs->opaque; + int i; + + for (i =3D 0; i < s->num_children; i++) { + /* + * We have no idea whether our children show the same data as + * this node (@bs). It is actually highly likely that + * @to_replace does not, because replacing a broken child is + * one of the main use cases here. + * + * We do know that the new BDS will match @bs, so replacing + * any of our children by it will be safe. It cannot change + * the data this quorum node presents to its parents. + * + * However, replacing @to_replace by @bs in any of our + * children's chains may change visible data somewhere in + * there. We therefore cannot recurse down those chains with + * bdrv_recurse_can_replace(). + * (More formally, bdrv_recurse_can_replace() requires that + * @to_replace will be replaced by something matching the @bs + * passed to it. We cannot guarantee that.) + * + * Thus, we can only check whether any of our immediate + * children matches @to_replace. + * + * (In the future, we might add a function to recurse down a + * chain that checks that nothing there cares about a change + * in data from the respective child in question. For + * example, most filters do not care when their child's data + * suddenly changes, as long as their parents do not care.) + */ + if (s->children[i]->bs =3D=3D to_replace) { + /* + * We now have to ensure that there is no other parent + * that cares about replacing this child by a node with + * potentially different data. + * We do so by checking whether there are any other parents + * at all, which is stricter than necessary, but also very + * simple. (We may decide to implement something more + * complex and permissive when there is an actual need for + * it.) + */ + return QLIST_FIRST(&to_replace->parents) =3D=3D s->children[i]= && + QLIST_NEXT(s->children[i], next_parent) =3D=3D NULL; + } + } + + return false; +} + static int quorum_valid_threshold(int threshold, int num_children, Error *= *errp) { =20 @@ -1164,6 +1217,7 @@ static BlockDriver bdrv_quorum =3D { =20 .is_filter =3D true, .bdrv_recurse_is_first_non_filter =3D quorum_recurse_is_first_non_fi= lter, + .bdrv_recurse_can_replace =3D quorum_recurse_can_replace, =20 .strong_runtime_opts =3D quorum_strong_runtime_opts, }; --=20 2.24.1