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[libvirt] [PATCH 14/7] snapshot: virsh shorthand for operating on current snap



Rather than having to do:

$ virsh snapshot-revert dom $(virsh snapshot-current dom --name)

I thought it would be nice to do:

$ virsh snaphot-revert dom --current

I intentionally made it so that omitting both --current and a name
is an error (having the absence of a name imply --current seems
just a bit too magic, so --current must be explicit).

I didn't add 'virsh snapshot-dumpxml --current' since we already
have 'virsh snapshot-current' for the same task.  All other
snapshot-* options that take a snapshotname now take --current in
its place; while keeping snapshot-edit backwards-compatible.

* tools/virsh.c (vshLookupSnapshot): New helper function.
(cmdSnapshotEdit, cmdSnapshotList, cmdSnapshotParent)
(cmdSnapshotDelete, cmdDomainSnapshotRevert): Use it, adding an
option where needed.
* tools/virsh.pod (snapshot-delete, snapshot-edit)
(snapshot-list, snapshot-parent, snapshot-revert): Document
use of --current.
(snapshot-dumpxml): Mention alternative.
---

Does not strictly depend on virDomainSnapshotNumChildren, other
than the fact that I'm touching 'virsh snapshot-list dom --from name'
to add 'virsh snapshot-list dom --current'; I could split that
change out from the rest of the patch if desired to get the ease-of-use
in the other snapshot-* commands before the new API is approved.

 tools/virsh.c   |  109 ++++++++++++++++++++++++++++++++++++-------------------
 tools/virsh.pod |   31 ++++++++++------
 2 files changed, 90 insertions(+), 50 deletions(-)

diff --git a/tools/virsh.c b/tools/virsh.c
index 86b230d..ea7b56b 100644
--- a/tools/virsh.c
+++ b/tools/virsh.c
@@ -12816,6 +12816,48 @@ cleanup:
     return ret;
 }

+/* Helper for resolving {--current | --ARG name} into a snapshot
+ * belonging to DOM.  If EXCLUSIVE, fail if both --current and arg are
+ * present.  On success, populate *SNAP, and if NAME is not NULL,
+ * *NAME, before returning 0.  On failure, return -1 after issuing an
+ * error message.  */
+static int
+vshLookupSnapshot(vshControl *ctl, const vshCmd *cmd,
+                  const char *arg, bool exclusive, virDomainPtr dom,
+                  virDomainSnapshotPtr *snap, const char **name)
+{
+    bool current = vshCommandOptBool(cmd, "current");
+    const char *snapname = NULL;
+
+    if (vshCommandOptString(cmd, arg, &snapname) < 0) {
+        vshError(ctl, _("invalid argument for --%s"), arg);
+        return -1;
+    }
+
+    if (exclusive && current && snapname) {
+        vshError(ctl, _("--%s and --current are mutually exclusive"), arg);
+        return -1;
+    }
+
+    if (snapname) {
+        *snap = virDomainSnapshotLookupByName(dom, snapname, 0);
+    } else if (current) {
+        *snap = virDomainSnapshotCurrent(dom, 0);
+    } else {
+        vshError(ctl, _("--%s or --current is required"), arg);
+        return -1;
+    }
+    if (!*snap) {
+        virshReportError(ctl);
+        return -1;
+    }
+
+    if (name && *snap)
+        *name = vshStrdup(ctl, virDomainSnapshotGetName(*snap));
+
+    return 0;
+}
+
 /*
  * "snapshot-edit" command
  */
@@ -12827,7 +12869,7 @@ static const vshCmdInfo info_snapshot_edit[] = {

 static const vshCmdOptDef opts_snapshot_edit[] = {
     {"domain", VSH_OT_DATA, VSH_OFLAG_REQ, N_("domain name, id or uuid")},
-    {"snapshotname", VSH_OT_DATA, VSH_OFLAG_REQ, N_("snapshot name")},
+    {"snapshotname", VSH_OT_DATA, 0, N_("snapshot name")},
     {"current", VSH_OT_BOOL, 0, N_("also set edited snapshot as current")},
     {NULL, 0, 0, NULL}
 };
@@ -12845,21 +12887,19 @@ cmdSnapshotEdit(vshControl *ctl, const vshCmd *cmd)
     unsigned int getxml_flags = VIR_DOMAIN_XML_SECURE;
     unsigned int define_flags = VIR_DOMAIN_SNAPSHOT_CREATE_REDEFINE;

-    if (vshCommandOptBool(cmd, "current"))
+    if (vshCommandOptBool(cmd, "current") &&
+        vshCommandOptBool(cmd, "snapshotname"))
         define_flags |= VIR_DOMAIN_SNAPSHOT_CREATE_CURRENT;

     if (!vshConnectionUsability(ctl, ctl->conn))
         return false;

-    if (vshCommandOptString(cmd, "snapshotname", &name) <= 0)
-        goto cleanup;
-
     dom = vshCommandOptDomain(ctl, cmd, NULL);
     if (dom == NULL)
         goto cleanup;

-    snapshot = virDomainSnapshotLookupByName(dom, name, 0);
-    if (snapshot == NULL)
+    if (vshLookupSnapshot(ctl, cmd, "snapshotname", false, dom,
+                          &snapshot, &name) < 0)
         goto cleanup;

     /* Get the XML configuration of the snapshot.  */
@@ -13109,6 +13149,8 @@ static const vshCmdOptDef opts_snapshot_list[] = {
      N_("list only snapshots that have metadata that would prevent undefine")},
     {"tree", VSH_OT_BOOL, 0, N_("list snapshots in a tree")},
     {"from", VSH_OT_DATA, 0, N_("limit list to children of given snapshot")},
+    {"current", VSH_OT_BOOL, 0,
+     N_("limit list to children of current snapshot")},
     {"descendants", VSH_OT_BOOL, 0, N_("with --from, list all descendants")},
     {NULL, 0, 0, NULL}
 };
@@ -13142,10 +13184,17 @@ cmdSnapshotList(vshControl *ctl, const vshCmd *cmd)
     int start_index = -1;
     bool descendants = false;

-    if (vshCommandOptString(cmd, "from", &from) < 0) {
-        vshError(ctl, _("invalid from argument '%s'"), from);
+    if (!vshConnectionUsability(ctl, ctl->conn))
+        goto cleanup;
+
+    dom = vshCommandOptDomain(ctl, cmd, NULL);
+    if (dom == NULL)
+        goto cleanup;
+
+    if ((vshCommandOptBool(cmd, "from") ||
+         vshCommandOptBool(cmd, "current")) &&
+        vshLookupSnapshot(ctl, cmd, "from", true, dom, &start, &from) < 0)
         goto cleanup;
-    }

     if (vshCommandOptBool(cmd, "parent")) {
         if (vshCommandOptBool(cmd, "roots")) {
@@ -13176,18 +13225,8 @@ cmdSnapshotList(vshControl *ctl, const vshCmd *cmd)
         flags |= VIR_DOMAIN_SNAPSHOT_LIST_METADATA;
     }

-    if (!vshConnectionUsability(ctl, ctl->conn))
-        goto cleanup;
-
-    dom = vshCommandOptDomain(ctl, cmd, NULL);
-    if (dom == NULL)
-        goto cleanup;
-
     if (from) {
         descendants = vshCommandOptBool(cmd, "descendants");
-        start = virDomainSnapshotLookupByName(dom, from, 0);
-        if (!start)
-            goto cleanup;
         if (descendants || tree) {
             flags |= VIR_DOMAIN_SNAPSHOT_LIST_DESCENDANTS;
         }
@@ -13519,7 +13558,8 @@ static const vshCmdInfo info_snapshot_parent[] = {

 static const vshCmdOptDef opts_snapshot_parent[] = {
     {"domain", VSH_OT_DATA, VSH_OFLAG_REQ, N_("domain name, id or uuid")},
-    {"snapshotname", VSH_OT_DATA, VSH_OFLAG_REQ, N_("snapshot name")},
+    {"snapshotname", VSH_OT_DATA, 0, N_("find parent of snapshot name")},
+    {"current", VSH_OT_BOOL, 0, N_("find parent of current snapshot")},
     {NULL, 0, 0, NULL}
 };

@@ -13539,11 +13579,8 @@ cmdSnapshotParent(vshControl *ctl, const vshCmd *cmd)
     if (dom == NULL)
         goto cleanup;

-    if (vshCommandOptString(cmd, "snapshotname", &name) <= 0)
-        goto cleanup;
-
-    snapshot = virDomainSnapshotLookupByName(dom, name, 0);
-    if (snapshot == NULL)
+    if (vshLookupSnapshot(ctl, cmd, "snapshotname", true, dom,
+                          &snapshot, &name) < 0)
         goto cleanup;

     if (vshGetSnapshotParent(ctl, snapshot, &parent) < 0)
@@ -13578,7 +13615,8 @@ static const vshCmdInfo info_snapshot_revert[] = {

 static const vshCmdOptDef opts_snapshot_revert[] = {
     {"domain", VSH_OT_DATA, VSH_OFLAG_REQ, N_("domain name, id or uuid")},
-    {"snapshotname", VSH_OT_DATA, VSH_OFLAG_REQ, N_("snapshot name")},
+    {"snapshotname", VSH_OT_DATA, 0, N_("snapshot name")},
+    {"current", VSH_OT_BOOL, 0, N_("revert to current snapshot")},
     {"running", VSH_OT_BOOL, 0, N_("after reverting, change state to running")},
     {"paused", VSH_OT_BOOL, 0, N_("after reverting, change state to paused")},
     {"force", VSH_OT_BOOL, 0, N_("try harder on risky reverts")},
@@ -13614,11 +13652,8 @@ cmdDomainSnapshotRevert(vshControl *ctl, const vshCmd *cmd)
     if (dom == NULL)
         goto cleanup;

-    if (vshCommandOptString(cmd, "snapshotname", &name) <= 0)
-        goto cleanup;
-
-    snapshot = virDomainSnapshotLookupByName(dom, name, 0);
-    if (snapshot == NULL)
+    if (vshLookupSnapshot(ctl, cmd, "snapshotname", true, dom,
+                          &snapshot, &name) < 0)
         goto cleanup;

     result = virDomainRevertToSnapshot(snapshot, flags);
@@ -13654,7 +13689,8 @@ static const vshCmdInfo info_snapshot_delete[] = {

 static const vshCmdOptDef opts_snapshot_delete[] = {
     {"domain", VSH_OT_DATA, VSH_OFLAG_REQ, N_("domain name, id or uuid")},
-    {"snapshotname", VSH_OT_DATA, VSH_OFLAG_REQ, N_("snapshot name")},
+    {"snapshotname", VSH_OT_DATA, 0, N_("snapshot name")},
+    {"current", VSH_OT_BOOL, 0, N_("delete current snapshot")},
     {"children", VSH_OT_BOOL, 0, N_("delete snapshot and all children")},
     {"children-only", VSH_OT_BOOL, 0, N_("delete children but not snapshot")},
     {"metadata", VSH_OT_BOOL, 0,
@@ -13678,7 +13714,8 @@ cmdSnapshotDelete(vshControl *ctl, const vshCmd *cmd)
     if (dom == NULL)
         goto cleanup;

-    if (vshCommandOptString(cmd, "snapshotname", &name) <= 0)
+    if (vshLookupSnapshot(ctl, cmd, "snapshotname", true, dom,
+                          &snapshot, &name) < 0)
         goto cleanup;

     if (vshCommandOptBool(cmd, "children"))
@@ -13688,10 +13725,6 @@ cmdSnapshotDelete(vshControl *ctl, const vshCmd *cmd)
     if (vshCommandOptBool(cmd, "metadata"))
         flags |= VIR_DOMAIN_SNAPSHOT_DELETE_METADATA_ONLY;

-    snapshot = virDomainSnapshotLookupByName(dom, name, 0);
-    if (snapshot == NULL)
-        goto cleanup;
-
     /* XXX If we wanted, we could emulate DELETE_CHILDREN_ONLY even on
      * older servers that reject the flag, by manually computing the
      * list of descendants.  But that's a lot of code to maintain.  */
diff --git a/tools/virsh.pod b/tools/virsh.pod
index dd60a64..e1a9b86 100644
--- a/tools/virsh.pod
+++ b/tools/virsh.pod
@@ -1951,11 +1951,13 @@ the XML.
 With I<snapshotname>, this is a request to make the existing named
 snapshot become the current snapshot, without reverting the domain.

-=item B<snapshot-edit> I<domain> I<snapshotname> [I<--current>]
+=item B<snapshot-edit> I<domain> [I<snapshotname>] [I<--current>]

 Edit the XML configuration file for I<snapshotname> of a domain.  If
-I<--current> is specified, also force the edited snapshot to become
-the current snapshot.
+both I<snapshotname> and I<--current> are specified, also force the
+edited snapshot to become the current snapshot.  If I<snapshotname>
+is omitted, then I<--current> must be supplied, to edit the current
+snapshot.

 This is equivalent to:

@@ -1969,7 +1971,7 @@ The editor used can be supplied by the C<$VISUAL> or C<$EDITOR> environment
 variables, and defaults to C<vi>.

 =item B<snapshot-list> I<domain> [{I<--parent> | I<--roots> | I<--tree>}]
-[I<--metadata>] [[I<--from>] B<snapshot> [I<--descendants>]]
+[I<--metadata>] [{[I<--from>] B<snapshot> | I<--current>} [I<--descendants>]]

 List all of the available snapshots for the given domain, defaulting
 to show columns for the snapshot name, creation time, and domain state.
@@ -1981,7 +1983,8 @@ If I<--tree> is specified, the output will be in a tree format, listing
 just snapshot names.  These three options are mutually exclusive.

 If I<--from> is provided, filter the list to snapshots which are
-children of the given B<snapshot>.  When used in isolation or with
+children of the given B<snapshot>; or if I<--current> is provided,
+start at the current snapshot.  When used in isolation or with
 I<--parent>, the list is limited to direct children unless
 I<--descendants> is also present.  When used with I<--tree>, the
 use of I<--descendants> is implied.  This option is not compatible
@@ -1996,15 +1999,18 @@ a transient domain.

 Output the snapshot XML for the domain's snapshot named I<snapshot>.
 Using I<--security-info> will also include security sensitive information.
+Use B<snapshot-current> to easily access the XML of the current snapshot.

-=item B<snapshot-parent> I<domain> I<snapshot>
+=item B<snapshot-parent> I<domain> {I<snapshot> | I<--current>}

-Output the name of the parent snapshot for the given I<snapshot>, if any.
+Output the name of the parent snapshot, if any, for the given
+I<snapshot>, or for the current snapshot with I<--current>.

-=item B<snapshot-revert> I<domain> I<snapshot> [{I<--running> | I<--paused>}]
-[I<--force>]
+=item B<snapshot-revert> I<domain> {I<snapshot> | I<--current>}
+[{I<--running> | I<--paused>}] [I<--force>]

-Revert the given domain to the snapshot specified by I<snapshot>.  Be aware
+Revert the given domain to the snapshot specified by I<snapshot>, or to
+the current snapshot with I<--current>.  Be aware
 that this is a destructive action; any changes in the domain since the last
 snapshot was taken will be lost.  Also note that the state of the domain after
 snapshot-revert is complete will be the state of the domain at the time
@@ -2034,10 +2040,11 @@ snapshot that uses a provably incompatible configuration, as well as
 with an inactive snapshot that is combined with the I<--start> or
 I<--pause> flag.

-=item B<snapshot-delete> I<domain> I<snapshot> [I<--metadata>]
+=item B<snapshot-delete> I<domain> {I<snapshot> | I<--current>} [I<--metadata>]
 [{I<--children> | I<--children-only>}]

-Delete the snapshot for the domain named I<snapshot>.  If this snapshot
+Delete the snapshot for the domain named I<snapshot>, or the current
+snapshot with I<--current>.  If this snapshot
 has child snapshots, changes from this snapshot will be merged into the
 children.  If I<--children> is passed, then delete this snapshot and any
 children of this snapshot.  If I<--children-only> is passed, then delete
-- 
1.7.4.4


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