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/autofs4/root.c b/fs/autofs4/root.c
index f55ae23..87d95a8 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -583,6 +583,8 @@
 	if (!autofs4_oz_mode(sbi) && !capable(CAP_SYS_ADMIN))
 		return -EACCES;
 
+	dentry_unhash(dentry);
+
 	if (atomic_dec_and_test(&ino->count)) {
 		p_ino = autofs4_dentry_ino(dentry->d_parent);
 		if (p_ino && dentry->d_parent != dentry)