vfs: push dentry_unhash on rmdir into file systems

Only a few file systems need this.  Start by pushing it down into each
fs rmdir method (except gfs2 and xfs) so it can be dealt with on a per-fs
basis.

This does not change behavior for any in-tree file systems.

Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/omfs/dir.c

@@ -240,8 +240,12 @@ static int omfs_remove(struct inode *dir, struct dentry *dentry)
 	struct inode *inode = dentry->d_inode;
 	int ret;
 
-	if (S_ISDIR(inode->i_mode) && !omfs_dir_is_empty(inode))
-		return -ENOTEMPTY;
+
+	if (S_ISDIR(inode->i_mode)) {
+		dentry_unhash(dentry);
+		if (!omfs_dir_is_empty(inode))
+			return -ENOTEMPTY;
+	}
 
 	ret = omfs_delete_entry(dentry);
 	if (ret)