Convert obvious places to deactivate_locked_super()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/9p/vfs_super.c b/fs/9p/vfs_super.c
index 7d23214..0d29a57 100644
--- a/fs/9p/vfs_super.c
+++ b/fs/9p/vfs_super.c
@@ -174,10 +174,7 @@
 	return 0;
 
 release_sb:
-	if (sb) {
-		up_write(&sb->s_umount);
-		deactivate_super(sb);
-	}
+	deactivate_locked_super(sb);
 
 free_stat:
 	kfree(st);