tools/xenstore: start with empty data base

Today xenstored tries to open a tdb data base file on disk when it is
started. As this is problematic in most cases the scripts used to start
xenstored ensure xenstored won't find such a file in order to start
with an empty xenstore.

A tdb data base file can't be used to restore all Xenstore state as
e.g. Xenstore watches are not kept in the tdb data base. The file is
meant to be used for debugging purposes after a xenstored crash only.

Instead of opening a Xenstore data base file found on disk always start
with an empty data base. This will avoid problems in case someone is
testing multiple xenstored versions without rebooting (which is not
supported but helps debugging in some cases).

Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>

tools/xenstore/xenstored_core.c

@@ -1157,17 +1157,6 @@ static int _rm(struct connection *conn, const void *ctx, struct node *node,
 }
 
 
-static void internal_rm(const char *name)
-{
-	char *tname = talloc_strdup(NULL, name);
-	struct node *node = read_node(NULL, tname, tname);
-	if (node)
-		_rm(NULL, tname, node, tname);
-	talloc_free(node);
-	talloc_free(tname);
-}
-
-
 static int do_rm(struct connection *conn, struct buffered_data *in)
 {
 	struct node *node;
@@ -1582,49 +1571,18 @@ static void setup_structure(void)
 		barf_perror("Could not create tdbname");
 
 	if (!(tdb_flags & TDB_INTERNAL))
-		tdb_ctx = tdb_open_ex(tdbname, 0, tdb_flags, O_RDWR, 0,
-				      &tdb_logger, NULL);
+		unlink(tdbname);
 
-	if (tdb_ctx) {
-		/* XXX When we make xenstored able to restart, this will have
-		   to become cleverer, checking for existing domains and not
-		   removing the corresponding entries, but for now xenstored
-		   cannot be restarted without losing all the registered
-		   watches, which breaks all the backend drivers anyway.  We
-		   can therefore get away with just clearing /local and
-		   expecting Xend to put the appropriate entries back in.
+	tdb_ctx = tdb_open_ex(tdbname, 7919, tdb_flags, O_RDWR|O_CREAT|O_EXCL,
+			      0640, &tdb_logger, NULL);
+	if (!tdb_ctx)
+		barf_perror("Could not create tdb file %s", tdbname);
 
-		   When this change is made it is important to note that
-		   dom0's entries must be cleaned up on reboot _before_ this
-		   daemon starts, otherwise the backend drivers and dom0's
-		   balloon driver will pick up stale entries.  In the case of
-		   the balloon driver, this can be fatal.
-		*/
-		char *tlocal = talloc_strdup(NULL, "/local");
+	manual_node("/", "tool");
+	manual_node("/tool", "xenstored");
+	manual_node("/tool/xenstored", NULL);
 
-		check_store();
-
-		if (remove_local) {
-			internal_rm("/local");
-			create_node(NULL, NULL, tlocal, NULL, 0);
-
-			check_store();
-		}
-
-		talloc_free(tlocal);
-	}
-	else {
-		tdb_ctx = tdb_open_ex(tdbname, 7919, tdb_flags, O_RDWR|O_CREAT,
-				      0640, &tdb_logger, NULL);
-		if (!tdb_ctx)
-			barf_perror("Could not create tdb file %s", tdbname);
-
-		manual_node("/", "tool");
-		manual_node("/tool", "xenstored");
-		manual_node("/tool/xenstored", NULL);
-
-		check_store();
-	}
+	check_store();
 }