restore killability of old mutex_lock_killable(&inode->i_mutex) users

The ones that are taking it exclusive, that is...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/readdir.c b/fs/readdir.c
index 68ef06e..9d0212c 100644
--- a/fs/readdir.c
+++ b/fs/readdir.c
@@ -35,13 +35,13 @@
 	if (res)
 		goto out;
 
-	if (shared)
+	if (shared) {
 		inode_lock_shared(inode);
-	else
-		inode_lock(inode);
-	// res = mutex_lock_killable(&inode->i_mutex);
-	// if (res)
-	//	goto out;
+	} else {
+		res = down_write_killable(&inode->i_rwsem);
+		if (res)
+			goto out;
+	}
 
 	res = -ENOENT;
 	if (!IS_DEADDIR(inode)) {