[dm-devel] [PATCH V4 05/12] block: add new field into 'struct bvec_iter'

[Ming Lei]

There is a hole at the end of 'struct bvec_iter', so put a new field
here and we can save cookie returned from submit_bio() here for
supporting bio based polling.

This way can avoid to extend bio unnecessarily.

Meantime add two helpers to get/set this field.

Reviewed-by: Hannes Reinecke <hare at suse.de>
Signed-off-by: Ming Lei <ming.lei at redhat.com>
---
 block/blk.h          | 10 ++++++++++
 include/linux/bvec.h |  8 ++++++++
 2 files changed, 18 insertions(+)

diff --git a/block/blk.h b/block/blk.h
index 35901cee709d..c1d8456656df 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -395,4 +395,14 @@ static inline void blk_create_io_poll_context(struct request_queue *q)
 		bio_poll_ctx_alloc(ioc);
 }
 
+static inline unsigned int bio_get_private_data(struct bio *bio)
+{
+	return bio->bi_iter.bi_private_data;
+}
+
+static inline void bio_set_private_data(struct bio *bio, unsigned int data)
+{
+	bio->bi_iter.bi_private_data = data;
+}
+
 #endif /* BLK_INTERNAL_H */
diff --git a/include/linux/bvec.h b/include/linux/bvec.h
index ff832e698efb..547ad7526960 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -43,6 +43,14 @@ struct bvec_iter {
 
 	unsigned int            bi_bvec_done;	/* number of bytes completed in
 						   current bvec */
+
+	/*
+	 * There is a hole at the end of bvec_iter, add one new field to hold
+	 * something which isn't related with 'bvec_iter', so that we can
+	 * avoid extending bio. So far this new field is used for bio based
+	 * polling, we will store returning value of submit_bio() here.
+	 */
+	unsigned int		bi_private_data;
 };
 
 struct bvec_iter_all {
-- 
2.29.2