[dm-devel] [RFC PATCH 2/4] block: add field of .bi_bio_drv_data to bio

[Ming Lei]

After bio is submitted, bio->bi_next is used for IO merge for request
based queue only.

Reuse the filed for bio based driver for storing driver data, and name
it as .bi_bio_drv_data.

Signed-off-by: Ming Lei <ming.lei at redhat.com>
---
 include/linux/blk_types.h | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 6e6c2af48d74..acb45213338c 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -220,7 +220,16 @@ typedef unsigned int blk_qc_t;
  * stacking drivers)
  */
 struct bio {
-	struct bio		*bi_next;	/* request queue link */
+	union {
+		/* request queue link */
+		struct bio		*bi_next;
+
+		/*
+		 * once bio is submitted to bio based queue, driver can use
+		 * this field to store its own data
+		 */
+		void			*bi_bio_drv_data;
+	};
 	struct block_device	*bi_bdev;
 	unsigned int		bi_opf;		/* bottom bits req flags,
 						 * top bits REQ_OP. Use
-- 
2.31.1