new helper: daemonize_descriptors()

descriptor-related parts of daemonize, done right.  As the
result we simplify the locking rules for ->files - we
hold task_lock in *all* cases when we modify ->files.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

kernel/exit.c

@@ -457,9 +457,7 @@ void daemonize(const char *name, ...)
 	/* Become as one with the init task */
 
 	daemonize_fs_struct();
-	exit_files(current);
-	current->files = init_task.files;
-	atomic_inc(&current->files->count);
+	daemonize_descriptors();
 
 	reparent_to_kthreadd();
 }