dm: don't save and restore bi_private

Device mapper used the field bi_private to point to dm_target_io. However,
since kernel 3.15, the bi_private field is unused, and so the targets do
not need to save and restore this field.

This patch removes code that saves and restores bi_private from dm-cache,
dm-snapshot and dm-verity.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-cache-target.c

@@ -118,14 +118,12 @@ static void iot_io_end(struct io_tracker *iot, sector_t len)
  */
 struct dm_hook_info {
 	bio_end_io_t *bi_end_io;
-	void *bi_private;
 };
 
 static void dm_hook_bio(struct dm_hook_info *h, struct bio *bio,
 			bio_end_io_t *bi_end_io, void *bi_private)
 {
 	h->bi_end_io = bio->bi_end_io;
-	h->bi_private = bio->bi_private;
 
 	bio->bi_end_io = bi_end_io;
 	bio->bi_private = bi_private;
@@ -134,7 +132,6 @@ static void dm_hook_bio(struct dm_hook_info *h, struct bio *bio,
 static void dm_unhook_bio(struct dm_hook_info *h, struct bio *bio)
 {
 	bio->bi_end_io = h->bi_end_io;
-	bio->bi_private = h->bi_private;
 }
 
 /*----------------------------------------------------------------*/

drivers/md/dm-snap.c

@@ -207,7 +207,6 @@ struct dm_snap_pending_exception {
 	 */
 	struct bio *full_bio;
 	bio_end_io_t *full_bio_end_io;
-	void *full_bio_private;
 };
 
 /*
@@ -1485,10 +1484,8 @@ static void pending_complete(struct dm_snap_pending_exception *pe, int success)
 	snapshot_bios = bio_list_get(&pe->snapshot_bios);
 	origin_bios = bio_list_get(&pe->origin_bios);
 	full_bio = pe->full_bio;
-	if (full_bio) {
+	if (full_bio)
 		full_bio->bi_end_io = pe->full_bio_end_io;
-		full_bio->bi_private = pe->full_bio_private;
-	}
 	increment_pending_exceptions_done_count();
 
 	up_write(&s->lock);
@@ -1605,7 +1602,6 @@ static void start_full_bio(struct dm_snap_pending_exception *pe,
 
 	pe->full_bio = bio;
 	pe->full_bio_end_io = bio->bi_end_io;
-	pe->full_bio_private = bio->bi_private;
 
 	callback_data = dm_kcopyd_prepare_callback(s->kcopyd_client,
 						   copy_callback, pe);

drivers/md/dm-verity.c

@@ -83,9 +83,8 @@ struct dm_verity {
 struct dm_verity_io {
 	struct dm_verity *v;
 
-	/* original values of bio->bi_end_io and bio->bi_private */
+	/* original value of bio->bi_end_io */
 	bio_end_io_t *orig_bi_end_io;
-	void *orig_bi_private;
 
 	sector_t block;
 	unsigned n_blocks;
@@ -453,7 +452,6 @@ static void verity_finish_io(struct dm_verity_io *io, int error)
 	struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_bio_data_size);
 
 	bio->bi_end_io = io->orig_bi_end_io;
-	bio->bi_private = io->orig_bi_private;
 	bio->bi_error = error;
 
 	bio_endio(bio);
@@ -566,7 +564,6 @@ static int verity_map(struct dm_target *ti, struct bio *bio)
 	io = dm_per_bio_data(bio, ti->per_bio_data_size);
 	io->v = v;
 	io->orig_bi_end_io = bio->bi_end_io;
-	io->orig_bi_private = bio->bi_private;
 	io->block = bio->bi_iter.bi_sector >> (v->data_dev_block_bits - SECTOR_SHIFT);
 	io->n_blocks = bio->bi_iter.bi_size >> v->data_dev_block_bits;