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/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index 4d4cc6a..c88612f 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -521,6 +521,8 @@
 	struct dentry *lower_dir_dentry;
 	int rc;
 
+	dentry_unhash(dentry);
+
 	lower_dentry = ecryptfs_dentry_to_lower(dentry);
 	dget(dentry);
 	lower_dir_dentry = lock_parent(lower_dentry);