NFS: Fix atime revalidation in readdir()

NFSv3 will correctly update atime on a readdir call, so there is no need to
set the NFS_INO_INVALID_ATIME flag unless the call to nfs_refresh_inode()
fails.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index fd2c5c8..63850a8 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -288,6 +288,7 @@
 extern int nfs_sync_mapping(struct address_space *mapping);
 extern void nfs_zap_mapping(struct inode *inode, struct address_space *mapping);
 extern void nfs_zap_caches(struct inode *);
+extern void nfs_invalidate_atime(struct inode *);
 extern struct inode *nfs_fhget(struct super_block *, struct nfs_fh *,
 				struct nfs_fattr *);
 extern int nfs_refresh_inode(struct inode *, struct nfs_fattr *);