LUInstanceCreate: Acquire node allocation lock

Opportunistic locks are not yet used. This patch changes
LUInstanceCreate to acquire the node allocation lock to avoid conflicts
with other opcodes acquiring many node locks.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>

lib/cmdlib.py

@@ -9850,7 +9850,9 @@ class LUInstanceCreate(LogicalUnit):
       # specifying a group on instance creation and then selecting nodes from
       # that group
       self.needed_locks[locking.LEVEL_NODE] = locking.ALL_SET
-      self.needed_locks[locking.LEVEL_NODE_RES] = locking.ALL_SET
+      self.needed_locks[locking.LEVEL_NODE_RES] = \
+        _CopyLockList(self.needed_locks[locking.LEVEL_NODE])
+      self.needed_locks[locking.LEVEL_NODE_ALLOC] = locking.ALL_SET
     else:
       self.op.pnode = _ExpandNodeName(self.cfg, self.op.pnode)
       nodelist = [self.op.pnode]
@@ -9872,6 +9874,7 @@ class LUInstanceCreate(LogicalUnit):
       if src_node is None:
         self.needed_locks[locking.LEVEL_NODE] = locking.ALL_SET
+        self.needed_locks[locking.LEVEL_NODE_ALLOC] = locking.ALL_SET
         self.op.src_node = None
         if os.path.isabs(src_path):
           raise errors.OpPrereqError("Importing an instance from a path"
@@ -10255,12 +10258,14 @@ class LUInstanceCreate(LogicalUnit):
       self._RunAllocator()
     # Release all unneeded node locks
-    _ReleaseLocks(self, locking.LEVEL_NODE,
-                  keep=filter(None, [self.op.pnode, self.op.snode,
-                                     self.op.src_node]))
-    _ReleaseLocks(self, locking.LEVEL_NODE_RES,
-                  keep=filter(None, [self.op.pnode, self.op.snode,
-                                     self.op.src_node]))
+    keep_locks = filter(None, [self.op.pnode, self.op.snode, self.op.src_node])
+    _ReleaseLocks(self, locking.LEVEL_NODE, keep=keep_locks)
+    _ReleaseLocks(self, locking.LEVEL_NODE_RES, keep=keep_locks)
+    _ReleaseLocks(self, locking.LEVEL_NODE_ALLOC)
+
+    assert (self.owned_locks(locking.LEVEL_NODE) ==
+            self.owned_locks(locking.LEVEL_NODE_RES)), \
+      "Node locks differ from node resource locks"
     #### node related checks
@@ -10485,6 +10490,7 @@ class LUInstanceCreate(LogicalUnit):
     assert not (self.owned_locks(locking.LEVEL_NODE_RES) -
                 self.owned_locks(locking.LEVEL_NODE)), \
       "Node locks differ from node resource locks"
+    assert not self.glm.is_owned(locking.LEVEL_NODE_ALLOC)
     ht_kind = self.op.hypervisor
     if ht_kind in constants.HTS_REQ_PORT: