NFSv4.1: allow nfs_fhget to succeed with mounted on fileid

Commit 28331a46d88459788c8fca72dbb0415cd7f514c9 "Ensure we request the
ordinary fileid when doing readdirplus"
changed the meaning of NFS_ATTR_FATTR_FILEID which used to be set when
FATTR4_WORD1_MOUNTED_ON_FILED was requested.

Allow nfs_fhget to succeed with only a mounted on fileid when crossing
a mountpoint or a referral.

Ask for the fileid of the absent file system if mounted_on_fileid is not
supported.

Signed-off-by: Andy Adamson <andros@netapp.com>
cc:stable@kernel.org [2.6.39]
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 3f1eb81..6f4850d 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -256,7 +256,8 @@
 
 	nfs_attr_check_mountpoint(sb, fattr);
 
-	if ((fattr->valid & NFS_ATTR_FATTR_FILEID) == 0 && (fattr->valid & NFS_ATTR_FATTR_MOUNTPOINT) == 0)
+	if (((fattr->valid & NFS_ATTR_FATTR_FILEID) == 0) &&
+	    !nfs_attr_use_mounted_on_fileid(fattr))
 		goto out_no_inode;
 	if ((fattr->valid & NFS_ATTR_FATTR_TYPE) == 0)
 		goto out_no_inode;