CIFS: Don't let read only caching for mandatory byte-range locked files

If we have mandatory byte-range locks on a file we can't cache reads
because pagereading may have conflicts with these locks on the server.
That's why we should allow level2 oplocks for files without mandatory
locks only.

Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index dfab450..e6899ce 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -386,6 +386,7 @@
 	unsigned int	cap_unix;
 	unsigned int	cap_nt_find;
 	unsigned int	cap_large_files;
+	unsigned int	oplock_read;
 };
 
 #define HEADER_SIZE(server) (server->vals->header_size)