From patchwork Tue Feb 18 14:07:11 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Wolf X-Patchwork-Id: 11388597 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 DB996930 for ; Tue, 18 Feb 2020 14:19:47 +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 B28E22176D for ; Tue, 18 Feb 2020 14:19:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="JuARuiQI" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B28E22176D 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+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Received: from localhost ([::1]:35986 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j43j0-0006hP-Qz for patchwork-qemu-devel@patchwork.kernel.org; Tue, 18 Feb 2020 09:19:46 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:53232) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j43Y5-0007vd-Vi for qemu-devel@nongnu.org; Tue, 18 Feb 2020 09:08:31 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1j43Y4-0001fQ-N0 for qemu-devel@nongnu.org; Tue, 18 Feb 2020 09:08:29 -0500 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:32048 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1j43Y4-0001ew-Ic for qemu-devel@nongnu.org; Tue, 18 Feb 2020 09:08:28 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1582034908; 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=fNYLmRhzs0r/GjFjAcsYVbEpqUdZhUJgii0xaHZP438=; b=JuARuiQIShnYtx84vfOR0DefZchQqkpq1BXq/kLnCYvtweyD5As990ikBVm+K1j20YIZVl 8fKJUHF5oX344hgulek1QcyOpYC5iPOFBoSVFduBAZ/WTEyWrQeES+Pa4evgdi5ofwGYXz J3PXfhztzyZubl0DVGvXvvRk3qGJi+s= 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-110-xGPXqA1GO_6FTAIxIpsWKw-1; Tue, 18 Feb 2020 09:08:26 -0500 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 27880DB60; Tue, 18 Feb 2020 14:08:25 +0000 (UTC) Received: from linux.fritz.box.com (ovpn-117-181.ams2.redhat.com [10.36.117.181]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2055D19E9C; Tue, 18 Feb 2020 14:08:23 +0000 (UTC) From: Kevin Wolf To: qemu-block@nongnu.org Subject: [PULL 25/36] quorum: Implement .bdrv_recurse_can_replace() Date: Tue, 18 Feb 2020 15:07:11 +0100 Message-Id: <20200218140722.23876-26-kwolf@redhat.com> In-Reply-To: <20200218140722.23876-1-kwolf@redhat.com> References: <20200218140722.23876-1-kwolf@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-MC-Unique: xGPXqA1GO_6FTAIxIpsWKw-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.61 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: kwolf@redhat.com, peter.maydell@linaro.org, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" From: Max Reitz Signed-off-by: Max Reitz Message-Id: <20200218103454.296704-9-mreitz@redhat.com> Signed-off-by: Kevin Wolf --- 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(BlockDriverState *bs, return false; } +static bool quorum_recurse_can_replace(BlockDriverState *bs, + BlockDriverState *to_replace) +{ + BDRVQuorumState *s = bs->opaque; + int i; + + for (i = 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 == 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) == s->children[i] && + QLIST_NEXT(s->children[i], next_parent) == NULL; + } + } + + return false; +} + static int quorum_valid_threshold(int threshold, int num_children, Error **errp) { @@ -1164,6 +1217,7 @@ static BlockDriver bdrv_quorum = { .is_filter = true, .bdrv_recurse_is_first_non_filter = quorum_recurse_is_first_non_filter, + .bdrv_recurse_can_replace = quorum_recurse_can_replace, .strong_runtime_opts = quorum_strong_runtime_opts, };