NFS: Be more aggressive in using readdirplus for 'ls -l' situations

Try to detect 'ls -l' by having nfs_getattr() look at whether or not
there is an opendir() file descriptor for the parent directory.
If so, then assume that we want to force use of readdirplus in order
to avoid the multiple GETATTR calls over the wire.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index 0ae5807..f55a90b 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -92,6 +92,7 @@
 };
 
 struct nfs_open_dir_context {
+	struct list_head list;
 	struct rpc_cred *cred;
 	unsigned long attr_gencount;
 	__u64 dir_cookie;