NFS: Fix a connectathon regression in NFSv3 and NFSv4

We're failing basic test6 against Linux servers because they lack a correct
change attribute. The fix is to assume that we always want to invalidate
the readdir caches when we call update_changeattr and/or
nfs_post_op_update_inode on a directory.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 4693879..c44cd02 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -876,11 +876,19 @@
 {
 	struct nfs_inode *nfsi = NFS_I(inode);
 
-	if (fattr->valid & NFS_ATTR_FATTR)
+	if (fattr->valid & NFS_ATTR_FATTR) {
+		if (S_ISDIR(inode->i_mode)) {
+			spin_lock(&inode->i_lock);
+			nfsi->cache_validity |= NFS_INO_INVALID_DATA;
+			spin_unlock(&inode->i_lock);
+		}
 		return nfs_refresh_inode(inode, fattr);
+	}
 
 	spin_lock(&inode->i_lock);
 	nfsi->cache_validity |= NFS_INO_INVALID_ACCESS|NFS_INO_INVALID_ATTR|NFS_INO_REVAL_PAGECACHE;
+	if (S_ISDIR(inode->i_mode))
+		nfsi->cache_validity |= NFS_INO_INVALID_DATA;
 	spin_unlock(&inode->i_lock);
 	return 0;
 }