dm-verity: remove the unused "data_start" variable

Remove the unused "data_start" variable. It is always set to zero and the
user can't override it. If the user needs to use some existing offset
within a block device, it is possible to use the linear target.

Signed-off-by: Mikulas Patocka <[e-mail]>

drivers/md/dm-verity-target.c

···
  */
 static sector_t verity_map_sector(struct dm_verity *v, sector_t bi_sector)
 {
-	return v->data_start + dm_target_offset(v->ti, bi_sector);
+	return dm_target_offset(v->ti, bi_sector);
 }
 
 /*
···
 
 	*bdev = v->data_dev->bdev;
 
-	if (v->data_start || ti->len != bdev_nr_sectors(v->data_dev->bdev))
+	if (ti->len != bdev_nr_sectors(v->data_dev->bdev))
 		return 1;
 	return 0;
 }
···
 {
 	struct dm_verity *v = ti->private;
 
-	return fn(ti, v->data_dev, v->data_start, ti->len, data);
+	return fn(ti, v->data_dev, 0, ti->len, data);
 }
 
 static void verity_io_hints(struct dm_target *ti, struct queue_limits *limits)

drivers/md/dm-verity.h

···
 	unsigned int sig_size;	/* root digest signature size */
 #endif /* CONFIG_SECURITY */
 	unsigned int salt_size;
-	sector_t data_start;	/* data offset in 512-byte sectors */
 	sector_t hash_start;	/* hash start in blocks */
 	sector_t data_blocks;	/* the number of data blocks */
 	sector_t hash_blocks;	/* the number of hash blocks */