NVMe: Disk IO statistics

Add io stats accounting for bio requests so nvme block devices show
useful disk stats.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>
diff --git a/include/linux/nvme.h b/include/linux/nvme.h
index f451c8d..5d7c079 100644
--- a/include/linux/nvme.h
+++ b/include/linux/nvme.h
@@ -572,6 +572,7 @@
 	int offset;		/* Of PRP list */
 	int nents;		/* Used in scatterlist */
 	int length;		/* Of data, in bytes */
+	unsigned long start_time;
 	dma_addr_t first_dma;
 	struct scatterlist sg[0];
 };