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>
diff --git a/fs/hpfs/namei.c b/fs/hpfs/namei.c
index b1c72a9..b9fe158 100644
--- a/fs/hpfs/namei.c
+++ b/fs/hpfs/namei.c
@@ -461,6 +461,8 @@
 	int err;
 	int r;
 
+	dentry_unhash(dentry);
+
 	hpfs_adjust_length(name, &len);
 	hpfs_lock(dir->i_sb);
 	mutex_lock(&hpfs_i(inode)->i_parent_mutex);