[PATCH vfs-2.6 2/6] vfs: add d_ancestor()

This adds d_ancestor() instead of d_isparent(), then use it.

If new_dentry == old_dentry, is_subdir() returns 1, looks strange.
"new_dentry == old_dentry" is not subdir obviously. But I'm not
checking callers for now, so this keeps current behavior.

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>

include/linux/dcache.h

@@ -287,6 +287,7 @@ static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *in
 
 /* used for rename() and baskets */
 extern void d_move(struct dentry *, struct dentry *);
+extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
 
 /* appendix may either be NULL or be used for transname suffixes */
 extern struct dentry * d_lookup(struct dentry *, struct qstr *);