use S_ISDIR() in link_path_walk() to decide whether the last path component is a directory

Hi,

This patch does not allow open(name, O_DIRECTORY) to be successful for non-directories in reiser4. It replaces ->i_op->lookup != NULL "is dir" check for the last path component by explicit S_ISDIR(->i_mode) check.

Regardless to reiser4, S_ISDIR() looks more clear there.

Thanks in advance.

===== fs/namei.c 1.104 vs edited =====

@@ -816,7 +816,7 @@
 			break;
 		if (lookup_flags & LOOKUP_DIRECTORY) {
 			err = -ENOTDIR; 
-			if (!inode->i_op || !inode->i_op->lookup)
+			if (!S_ISDIR(inode->i_mode))
 				break;
 		}
 		goto return_base;

The only objection here is that right now we are guaranteed that cwd and root of every task have non-NULL ->lookup(). With your patch all we have is S_ISDIR().

So we either need to check for non-NULL ->lookup() before the beginning of loop in link_path_walk() or split the flag in two. I would rather do the former...