fix(instances): snapshot tab reads less and fails less

The snapshot tab listed the VM's snapshots three times per page: once
per kind and once more for all of them. The list of all is now made
from the two kinds, so the combined flag is no longer used anywhere.

The revert confirm named only the disks the persistent definition
would lose. A disk hot-plugged into the running VM alone is detached
too, so the live definition is compared with what ran when the
snapshot was taken.

A storage pool refresh error after libvirt had already made, reverted
or deleted the snapshot was shown as if the operation had failed. It
is now logged, and the left-behind check is skipped then, since a stale
pool still lists the removed files. A volume removed while that check
reads it is skipped too.

An error reading the block jobs no longer breaks the instance page;
create, revert and delete still query the jobs again and refuse.

vrtManager/instance.py

@@ -1574,7 +1574,7 @@ class wvmInstance(wvmConnect):
         if not memory:
             flags |= VIR_DOMAIN_SNAPSHOT_CREATE_DISK_ONLY
         self._snapshotCreateXML(xml, flags)
-        self.refresh_instance_pools()
+        self._refresh_pools_after_snapshot()
 
     def _snapshot_memory_xml(self, name, tree):
         """The <memory> element of a snapshot that saves memory: a file in the
@@ -1664,14 +1664,28 @@ class wvmInstance(wvmConnect):
                 points.update(self._disk_sources(saved).values())
         return disks, own, points | own
 
+    def _refresh_pools_after_snapshot(self):
+        """Refresh the pools once libvirt has changed the snapshot files. The
+        snapshot operation is done by then, so an error is only logged;
+        returns whether the pools are current."""
+        try:
+            self.refresh_instance_pools()
+        except libvirtError as err:
+            logger.warning("Storage pools of %s were not refreshed after a snapshot change: %s", self.instance.name(), err)
+            return False
+        return True
+
     def _left_behind(self, before):
         """Files libvirt merged or discarded but could not remove: it only
         logs a warning then (on NFS it removes them as the qemu user, who
         needs write access to their directory). Only a snapshot's own file or
         an overlay on a snapshot point counts; a disk a revert detached is
-        kept on purpose. A file outside every storage pool is not checked."""
+        kept on purpose. A file outside every storage pool is not checked,
+        nor is anything when the pools could not be refreshed: a stale pool
+        still lists the removed files."""
         disks, own, points = before
-        self.refresh_instance_pools()
+        if not self._refresh_pools_after_snapshot():
+            return []
         now_disks, now_own, _ = self._snapshot_files()
         # only disks still attached: one a revert detached keeps its files,
         # whatever they sit on
@@ -1680,10 +1694,11 @@ class wvmInstance(wvmConnect):
         for path in sorted((attached | own) - set().union(now_own, *now_disks.values())):
             try:
                 vol = self.get_volume_by_path(path)
-            except libvirtError:
+                if path not in own and util.get_xml_path(vol.XMLDesc(0), "/volume/backingStore/path") not in points:
+                    continue
+            except libvirtError:  # not in a pool, or removed meanwhile
                 continue
-            if path in own or util.get_xml_path(vol.XMLDesc(0), "/volume/backingStore/path") in points:
-                left.append(path)
+            left.append(path)
         return left
 
     @staticmethod
@@ -1703,15 +1718,23 @@ class wvmInstance(wvmConnect):
 
     def get_snapshot(self, flag):
         """Snapshots of one kind (VIR_DOMAIN_SNAPSHOT_LIST_INTERNAL or
-        _EXTERNAL; both flags for all), with whether each saved memory, is the
-        current one, and which disks of the persistent definition a revert to
-        it detaches."""
-        current_disks = self._disk_sources(self._XMLDesc(PERSISTENT_XML))
+        _EXTERNAL), with whether each saved memory, is the current one, and
+        which disks a revert to it detaches: from the persistent definition,
+        and on a running VM from the live one too (a disk hot-plugged only)."""
+        persistent_disks = self._disk_sources(self._XMLDesc(PERSISTENT_XML))
+        live_disks = self._disk_sources(self._XMLDesc(0)) if self.instance.isActive() else {}
         snapshots = []
         for snap in self.instance.listAllSnapshots(flag):
             tree = etree.fromstring(snap.getXMLDesc(0))
             definition = self._saved_definition(tree)
             saved_disks = self._disk_sources(definition) if definition is not None else {}
+            # a revert of a running VM restores what ran when the snapshot was taken
+            ran = tree.find("domain")
+            saved_live_disks = self._disk_sources(ran) if ran is not None else saved_disks
+            detaches = {dev: path for dev, path in persistent_disks.items() if dev not in saved_disks}
+            for dev, path in live_disks.items():
+                if dev not in saved_live_disks:
+                    detaches.setdefault(dev, path)
             snapshots.append(
                 {
                     "date": datetime.fromtimestamp(int(tree.findtext("creationTime"))),
@@ -1719,9 +1742,7 @@ class wvmInstance(wvmConnect):
                     "description": tree.findtext("description") or "",
                     "memory": tree.find("memory[@snapshot='external']") is not None,
                     "current": bool(snap.isCurrent(0)),
-                    "detaches": [
-                        {"dev": dev, "path": path} for dev, path in current_disks.items() if dev not in saved_disks
-                    ],
+                    "detaches": [{"dev": dev, "path": path} for dev, path in detaches.items()],
                 }
             )
         return snapshots