External/libvirt
1
0
Fork 0
mirror of https://gitlab.com/libvirt/libvirt.git synced 2025-01-11 15:27:47 +00:00
Code Issues Packages Projects Releases Wiki Activity

snapshots: Support topological visits

Browse Source 
Wire up support for VIR_DOMAIN_SNAPSHOT_LIST_TOPOLOGICAL in the
domain-agnostic support code.

Clients of snapshot_conf using virDomainSnapshotForEachDescendant()
are using a depth-first visit but with postfix visits of a given
node. Changing this to a prefix visit of the given node instantly
turns this into a topologically-ordered visit.  (A prefix
breadth-first visit would also be topologically sorted, but that
requires a queue while our recursion naturally has a stack).

With that change, we now always have a topological sort for
virDomainSnapshotListAllChildren() regardless of the new public API
flag. Then with one more tweak, we can also get a topological rather
than a faster random hash visit for virDomainListAllSnapshots(), by
doing a descendent walk from our internal metaroot (there, we let the
public API flag control behavior, because a topological sort DOES
require more stack and slightly more time).

Note that virDomainSnapshotForEach() still uses a random hash visit;
we could change that signature to take a tri-state for random, prefix,
or postfix visit if we ever had clients that cared about the
distinctions, but for now, none of the drivers seem to care.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
This commit is contained in:
Eric Blake 2019-03-07 22:29:55 -06:00
parent d16e5b15ed
commit b647d2195d
1 changed files with 10 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
src/conf/snapshot_conf.c
View File

@ -1213,9 +1213,10 @@ virDomainSnapshotObjListGetNames(virDomainSnapshotObjListPtr snapshots,
from = &snapshots->metaroot;
}
/* We handle LIST_ROOT/LIST_DESCENDANTS directly, mask that bit
* out to determine when we must use the filter callback. */
data.flags &= ~VIR_DOMAIN_SNAPSHOT_LIST_DESCENDANTS;
/* We handle LIST_ROOT/LIST_DESCENDANTS and LIST_TOPOLOGICAL directly,
* mask those bits out to determine when we must use the filter callback. */
data.flags &= ~(VIR_DOMAIN_SNAPSHOT_LIST_DESCENDANTS |
VIR_DOMAIN_SNAPSHOT_LIST_TOPOLOGICAL);
/* If this common code is being used, we assume that all snapshots
* have metadata, and thus can handle METADATA up front as an
@ -1240,7 +1241,11 @@ virDomainSnapshotObjListGetNames(virDomainSnapshotObjListPtr snapshots,
data.flags &= ~VIR_DOMAIN_SNAPSHOT_FILTERS_LOCATION;
if (flags & VIR_DOMAIN_SNAPSHOT_LIST_DESCENDANTS) {
if (from->def)
/* We could just always do a topological visit; but it is
* possible to optimize for less stack usage and time when a
* simpler full hashtable visit or counter will do. */
if (from->def || (names &&
(flags & VIR_DOMAIN_SNAPSHOT_LIST_TOPOLOGICAL)))
virDomainSnapshotForEachDescendant(from,
virDomainSnapshotObjListCopyNames,
&data);
@ -1327,10 +1332,10 @@ virDomainSnapshotActOnDescendant(void *payload,
virDomainSnapshotObjPtr obj = payload;
struct snapshot_act_on_descendant *curr = data;
(curr->iter)(payload, name, curr->data);
curr->number += 1 + virDomainSnapshotForEachDescendant(obj,
curr->iter,
curr->data);
(curr->iter)(payload, name, curr->data);
return 0;
}