Having struct bio allows us to do more in the genrate/verify_fn,
like copying a known good guard tag already available rather than
calculating it.

Index: linux-4.18.0/block/bio-integrity.c
===================================================================
--- linux-4.18.0.orig/block/bio-integrity.c
+++ linux-4.18.0/block/bio-integrity.c
@@ -209,17 +209,21 @@ static blk_status_t bio_integrity_proces
 	blk_status_t ret = BLK_STS_OK;
 	void *prot_buf = page_address(bip->bip_vec->bv_page) +
 		bip->bip_vec->bv_offset;
+	unsigned int i;
 
 	iter.disk_name = bio->bi_disk->disk_name;
 	iter.interval = 1 << bi->interval_exp;
 	iter.seed = proc_iter->bi_sector;
 	iter.prot_buf = prot_buf;
 
+	i = 0;
 	__bio_for_each_segment(bv, bio, bviter, *proc_iter) {
 		void *kaddr = kmap_atomic(bv.bv_page);
 
 		iter.data_buf = kaddr + bv.bv_offset;
 		iter.data_size = bv.bv_len;
+		iter.bi_idx = i;
+		iter.bio = bio;
 
 		ret = proc_fn(&iter);
 		if (ret) {
@@ -228,6 +232,7 @@ static blk_status_t bio_integrity_proces
 		}
 
 		kunmap_atomic(kaddr);
+		i++;
 	}
 	return ret;
 }
Index: linux-4.18.0/include/linux/blkdev.h
===================================================================
--- linux-4.18.0.orig/include/linux/blkdev.h
+++ linux-4.18.0/include/linux/blkdev.h
@@ -1802,7 +1802,9 @@ struct blk_integrity_iter {
 	sector_t		seed;
 	unsigned int		data_size;
 	unsigned short		interval;
+	unsigned short		bi_idx;
 	const char		*disk_name;
+	struct bio		*bio;
 };
 
 typedef blk_status_t (integrity_processing_fn) (struct blk_integrity_iter *);