NFS: Fix the ftruncate() credential problem

ftruncate() access checking is supposed to be performed at open() time,
just like reads and writes.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/proc.c b/fs/nfs/proc.c
index 5c35b02..c7605587 100644
--- a/fs/nfs/proc.c
+++ b/fs/nfs/proc.c
@@ -129,6 +129,8 @@
 	sattr->ia_mode &= S_IALLUGO;
 
 	dprintk("NFS call  setattr\n");
+	if (sattr->ia_valid & ATTR_FILE)
+		msg.rpc_cred = nfs_file_cred(sattr->ia_file);
 	nfs_fattr_init(fattr);
 	status = rpc_call_sync(NFS_CLIENT(inode), &msg, 0);
 	if (status == 0)