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/jfs/namei.c

@@ -360,6 +360,8 @@ static int jfs_rmdir(struct inode *dip, struct dentry *dentry)
 
 	jfs_info("jfs_rmdir: dip:0x%p name:%s", dip, dentry->d_name.name);
 
+	dentry_unhash(dentry);
+
 	/* Init inode for quota operations. */
 	dquot_initialize(dip);
 	dquot_initialize(ip);