From nobody Mon Feb 9 08:55:03 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; envelope-from=libvir-list-bounces@redhat.com; helo=mx1.redhat.com; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=libvir-list-bounces@redhat.com; dmarc=pass(p=none dis=none) header.from=redhat.com Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by mx.zohomail.com with SMTPS id 1552025289532951.4498578640059; Thu, 7 Mar 2019 22:08:09 -0800 (PST) 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 mx1.redhat.com (Postfix) with ESMTPS id D1C4C3B7F; Fri, 8 Mar 2019 06:08:06 +0000 (UTC) Received: from colo-mx.corp.redhat.com (colo-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.20]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4355B19C70; Fri, 8 Mar 2019 06:08:05 +0000 (UTC) Received: from lists01.pubmisc.prod.ext.phx2.redhat.com (lists01.pubmisc.prod.ext.phx2.redhat.com [10.5.19.33]) by colo-mx.corp.redhat.com (Postfix) with ESMTP id 8FC19181A12C; Fri, 8 Mar 2019 06:08:01 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) by lists01.pubmisc.prod.ext.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id x2865F7b017301 for ; Fri, 8 Mar 2019 01:05:15 -0500 Received: by smtp.corp.redhat.com (Postfix) id 8018160C5F; Fri, 8 Mar 2019 06:05:15 +0000 (UTC) Received: from blue.redhat.com (ovpn-118-35.phx2.redhat.com [10.3.118.35]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2B50E60BE5 for ; Fri, 8 Mar 2019 06:05:15 +0000 (UTC) From: Eric Blake To: libvir-list@redhat.com Date: Fri, 8 Mar 2019 00:05:08 -0600 Message-Id: <20190308060512.17733-2-eblake@redhat.com> In-Reply-To: <20190308060512.17733-1-eblake@redhat.com> References: <20190308060512.17733-1-eblake@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-loop: libvir-list@redhat.com Subject: [libvirt] [PATCH 1/5] snapshots: Add flag to guarantee topological sort X-BeenThere: libvir-list@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: Development discussions about the libvirt library & tools List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: quoted-printable Sender: libvir-list-bounces@redhat.com Errors-To: libvir-list-bounces@redhat.com X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Fri, 08 Mar 2019 06:08:08 +0000 (UTC) Content-Type: text/plain; charset="utf-8" When doing REDEFINE on multiple snapshot metadata XML descriptions, we require that a child cannot be redefined before its parent. Since libvirt already tracks a DAG, it is more convenient if we can ensure that virDomainListAllSnapshots() and friends have a way to return data in an order that we can directly reuse, rather than having to post-process the data ourselves to reconstruct the DAG. Add VIR_DOMAIN_SNAPSHOT_LIST_TOPOLOGICAL as our new guarantee (well, a guarantee at the time of the API call conclusion; there's always a possible TOCTTOU race where someone redefining snapshots in between the API results and the client actually using the list might render the list out-of-date). Four listing APIs are directly benefitted by the new flag; additionally, since we document that the older racy ListNames interfaces should be sized by using the same flags on their Num counterparts, the Num interfaces must document when they accept (and ignore) the flag. Signed-off-by: Eric Blake Reviewed-by: Daniel P. Berrang=C3=A9 Reviewed-by: J=C3=A1n Tomko --- include/libvirt/libvirt-domain-snapshot.h | 4 +++ src/libvirt-domain-snapshot.c | 42 ++++++++++++++++++++++- 2 files changed, 45 insertions(+), 1 deletion(-) diff --git a/include/libvirt/libvirt-domain-snapshot.h b/include/libvirt/li= bvirt-domain-snapshot.h index d9b689abbd..602e5def59 100644 --- a/include/libvirt/libvirt-domain-snapshot.h +++ b/include/libvirt/libvirt-domain-snapshot.h @@ -135,6 +135,10 @@ typedef enum { VIR_DOMAIN_SNAPSHOT_LIST_EXTERNAL =3D (1 << 9), /* Filter by snapsh= ots that use files ext= ernal to disk images */ + + VIR_DOMAIN_SNAPSHOT_LIST_TOPOLOGICAL =3D (1 << 10), /* Ensure parents = occur + before children in + the resulting lis= t */ } virDomainSnapshotListFlags; /* Return the number of snapshots for this domain */ diff --git a/src/libvirt-domain-snapshot.c b/src/libvirt-domain-snapshot.c index 11d84289f8..d133c84933 100644 --- a/src/libvirt-domain-snapshot.c +++ b/src/libvirt-domain-snapshot.c @@ -1,7 +1,7 @@ /* * libvirt-domain-snapshot.c: entry points for virDomainSnapshotPtr APIs * - * Copyright (C) 2006-2014 Red Hat, Inc. + * Copyright (C) 2006-2019 Red Hat, Inc. * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public @@ -298,6 +298,10 @@ virDomainSnapshotGetXMLDesc(virDomainSnapshotPtr snaps= hot, * * Provides the number of domain snapshots for this domain. * + * This function will accept VIR_DOMAIN_SNAPSHOT_LIST_TOPOLOGICAL in + * @flags only if virDomainSnapshotListNames() can honor it, although + * the flag has no other effect here. + * * By default, this command covers all snapshots; it is also possible to * limit things to just snapshots with no parents, when @flags includes * VIR_DOMAIN_SNAPSHOT_LIST_ROOTS. Additional filters are provided in @@ -369,6 +373,14 @@ virDomainSnapshotNum(virDomainPtr domain, unsigned int= flags) * their names in @names. The value to use for @nameslen can be determined * by virDomainSnapshotNum() with the same @flags. * + * If @flags contains VIR_DOMAIN_SNAPSHOT_LIST_TOPOLOGICAL, and no + * other connection is modifying snapshots, then it is guaranteed that + * for any snapshot in the resulting list, then no snapshots later in + * the list can be reached by a sequence of + * virDomainSnapshotGetParent() starting from that snapshot; + * otherwise, the order of snapshots in the resulting list is + * unspecified. + * * By default, this command covers all snapshots; it is also possible to * limit things to just snapshots with no parents, when @flags includes * VIR_DOMAIN_SNAPSHOT_LIST_ROOTS. Additional filters are provided in @@ -457,6 +469,14 @@ virDomainSnapshotListNames(virDomainPtr domain, char *= *names, int nameslen, * an array to store those objects. This API solves the race inherent in * virDomainSnapshotListNames(). * + * If @flags contains VIR_DOMAIN_SNAPSHOT_LIST_TOPOLOGICAL and @snaps + * is non-NULL, and no other connection is modifying snapshots, then + * it is guaranteed that for any snapshot in the resulting list, no + * snapshots later in the list can be reached by a sequence of + * virDomainSnapshotGetParent() starting from that snapshot; + * otherwise, the order of snapshots in the resulting list is + * unspecified. + * * By default, this command covers all snapshots; it is also possible to * limit things to just snapshots with no parents, when @flags includes * VIR_DOMAIN_SNAPSHOT_LIST_ROOTS. Additional filters are provided in @@ -533,6 +553,10 @@ virDomainListAllSnapshots(virDomainPtr domain, virDoma= inSnapshotPtr **snaps, * * Provides the number of child snapshots for this domain snapshot. * + * This function will accept VIR_DOMAIN_SNAPSHOT_LIST_TOPOLOGICAL in + * @flags only if virDomainSnapshotListChildrenNames() can honor it, + * although the flag has no other effect here. + * * By default, this command covers only direct children; it is also possib= le * to expand things to cover all descendants, when @flags includes * VIR_DOMAIN_SNAPSHOT_LIST_DESCENDANTS. Also, some filters are provided = in @@ -605,6 +629,14 @@ virDomainSnapshotNumChildren(virDomainSnapshotPtr snap= shot, unsigned int flags) * @nameslen can be determined by virDomainSnapshotNumChildren() with * the same @flags. * + * If @flags lacks VIR_DOMAIN_SNAPSHOT_LIST_DESCENDANTS or contains + * VIR_DOMAIN_SNAPSHOT_LIST_TOPOLOGICAL, and no other connection is + * modifying snapshots, then it is guaranteed that for any snapshot in + * the resulting list, no snapshots later in the list can be reached + * by a sequence of virDomainSnapshotGetParent() starting from that + * snapshot; otherwise, the order of snapshots in the resulting list + * is unspecified. + * * By default, this command covers only direct children; it is also possib= le * to expand things to cover all descendants, when @flags includes * VIR_DOMAIN_SNAPSHOT_LIST_DESCENDANTS. Also, some filters are provided = in @@ -697,6 +729,14 @@ virDomainSnapshotListChildrenNames(virDomainSnapshotPt= r snapshot, * snapshot, and allocate an array to store those objects. This API solves * the race inherent in virDomainSnapshotListChildrenNames(). * + * If @flags lacks VIR_DOMAIN_SNAPSHOT_LIST_DESCENDANTS or contains + * VIR_DOMAIN_SNAPSHOT_LIST_TOPOLOGICAL, @snaps is non-NULL, and no + * other connection is modifying snapshots, then it is guaranteed that + * for any snapshot in the resulting list, no snapshots later in the + * list can be reached by a sequence of virDomainSnapshotGetParent() + * starting from that snapshot; otherwise, the order of snapshots in + * the resulting list is unspecified. + * * By default, this command covers only direct children; it is also possib= le * to expand things to cover all descendants, when @flags includes * VIR_DOMAIN_SNAPSHOT_LIST_DESCENDANTS. Also, some filters are provided = in --=20 2.20.1 -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list