coda: add bdi backing to mount session

This ensures that dirty data gets flushed properly.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/include/linux/coda_psdev.h b/include/linux/coda_psdev.h
index 5b5d473..644062e8 100644
--- a/include/linux/coda_psdev.h
+++ b/include/linux/coda_psdev.h
@@ -1,6 +1,7 @@
 #ifndef __CODA_PSDEV_H
 #define __CODA_PSDEV_H
 
+#include <linux/backing-dev.h>
 #include <linux/magic.h>
 
 #define CODA_PSDEV_MAJOR 67
@@ -17,6 +18,7 @@
 	struct list_head    vc_processing;
 	int                 vc_inuse;
 	struct super_block *vc_sb;
+	struct backing_dev_info bdi;
 };