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snapshot: virsh fallback for snapshot-list --descendants --from
Given a list of snapshots and their parents, finding all descendants requires a hairy traversal. This code is O(n^3); it could maybe be made to scale O(n^2) with the use of a hash table, but that costs more memory. Hopefully there aren't too many people with a hierarchy so large as to approach REMOTE_DOMAIN_SNAPSHOT_LIST_NAMES_MAX (1024). * tools/virsh.c (cmdSnapshotList): Add final fallback.
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@ -13177,6 +13177,7 @@ cmdSnapshotList(vshControl *ctl, const vshCmd *cmd)
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bool tree = vshCommandOptBool(cmd, "tree");
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const char *from = NULL;
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virDomainSnapshotPtr start = NULL;
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int start_index = -1;
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bool descendants = false;
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if (vshCommandOptString(cmd, "from", &from) < 0) {
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@ -13231,10 +13232,8 @@ cmdSnapshotList(vshControl *ctl, const vshCmd *cmd)
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numsnaps = ctl->useSnapshotOld ? -1 :
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virDomainSnapshotNumChildren(start, flags);
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if (numsnaps < 0) {
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/* XXX also want to emulate --descendants without --tree */
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if ((!descendants || tree) &&
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(ctl->useSnapshotOld ||
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last_error->code == VIR_ERR_NO_SUPPORT)) {
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if (ctl->useSnapshotOld ||
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last_error->code == VIR_ERR_NO_SUPPORT) {
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/* We can emulate --from. */
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virFreeError(last_error);
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last_error = NULL;
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@ -13312,6 +13311,11 @@ cmdSnapshotList(vshControl *ctl, const vshCmd *cmd)
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if (tree || ctl->useSnapshotOld) {
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parents = vshCalloc(ctl, sizeof(char *), actual);
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for (i = (from && !ctl->useSnapshotOld); i < actual; i++) {
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if (ctl->useSnapshotOld && STREQ(names[i], from)) {
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start_index = i;
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continue;
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}
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/* free up memory from previous iterations of the loop */
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if (snapshot)
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virDomainSnapshotFree(snapshot);
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@ -13345,12 +13349,61 @@ cmdSnapshotList(vshControl *ctl, const vshCmd *cmd)
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goto cleanup;
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} else {
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if (ctl->useSnapshotOld && descendants) {
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/* XXX emulate --descendants as well */
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goto cleanup;
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bool changed = false;
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/* Make multiple passes over the list - first pass NULLs
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* out all roots except start, remaining passes NULL out
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* any entry whose parent is not still in list. Also, we
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* NULL out parent when name is known to be in list.
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* Sorry, this is O(n^3) - hope your hierarchy isn't huge. */
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if (start_index < 0) {
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vshError(ctl, _("snapshot %s disappeared from list"), from);
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goto cleanup;
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}
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for (i = 0; i < actual; i++) {
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if (i == start_index)
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continue;
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if (!parents[i]) {
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VIR_FREE(names[i]);
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} else if (STREQ(parents[i], from)) {
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VIR_FREE(parents[i]);
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changed = true;
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}
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}
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if (!changed) {
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ret = true;
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goto cleanup;
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}
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while (changed) {
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changed = false;
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for (i = 0; i < actual; i++) {
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bool found = false;
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int j;
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if (!names[i] || !parents[i])
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continue;
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for (j = 0; j < actual; j++) {
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if (!names[j] || i == j)
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continue;
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if (STREQ(parents[i], names[j])) {
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found = true;
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if (!parents[j])
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VIR_FREE(parents[i]);
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break;
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}
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}
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if (!found) {
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changed = true;
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VIR_FREE(names[i]);
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}
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}
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}
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VIR_FREE(names[start_index]);
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}
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for (i = 0; i < actual; i++) {
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if (ctl->useSnapshotOld && STRNEQ_NULLABLE(parents[i], from))
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if (ctl->useSnapshotOld &&
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(descendants ? !names[i] : STRNEQ_NULLABLE(parents[i], from)))
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continue;
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/* free up memory from previous iterations of the loop */
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