dm: move target request nr to dm_target_io

This patch moves target_request_nr from map_info to dm_target_io and
makes it accessible with dm_bio_get_target_request_nr.

This patch is a preparation for the next patch that removes map_info.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

drivers/md/dm-snap.c

@@ -1682,7 +1682,7 @@ static int snapshot_merge_map(struct dm_target *ti, struct bio *bio,
 	chunk_t chunk;
 
 	if (bio->bi_rw & REQ_FLUSH) {
-		if (!map_context->target_request_nr)
+		if (!dm_bio_get_target_request_nr(bio))
 			bio->bi_bdev = s->origin->bdev;
 		else
 			bio->bi_bdev = s->cow->bdev;

drivers/md/dm-stripe.c

@@ -279,13 +279,13 @@ static int stripe_map(struct dm_target *ti, struct bio *bio,
 	unsigned target_request_nr;
 
 	if (bio->bi_rw & REQ_FLUSH) {
-		target_request_nr = map_context->target_request_nr;
+		target_request_nr = dm_bio_get_target_request_nr(bio);
 		BUG_ON(target_request_nr >= sc->stripes);
 		bio->bi_bdev = sc->stripe[target_request_nr].dev->bdev;
 		return DM_MAPIO_REMAPPED;
 	}
 	if (unlikely(bio->bi_rw & REQ_DISCARD)) {
-		target_request_nr = map_context->target_request_nr;
+		target_request_nr = dm_bio_get_target_request_nr(bio);
 		BUG_ON(target_request_nr >= sc->stripes);
 		return stripe_map_discard(sc, bio, target_request_nr);
 	}

drivers/md/dm.c

@@ -1099,6 +1099,7 @@ static struct dm_target_io *alloc_tio(struct clone_info *ci,
 	tio->io = ci->io;
 	tio->ti = ti;
 	memset(&tio->info, 0, sizeof(tio->info));
+	tio->target_request_nr = 0;
 
 	return tio;
 }
@@ -1109,7 +1110,7 @@ static void __issue_target_request(struct clone_info *ci, struct dm_target *ti,
 	struct dm_target_io *tio = alloc_tio(ci, ti, ci->bio->bi_max_vecs);
 	struct bio *clone = &tio->clone;
 
-	tio->info.target_request_nr = request_nr;
+	tio->target_request_nr = request_nr;
 
 	/*
 	 * Discard requests require the bio's inline iovecs be initialized.

include/linux/device-mapper.h

@@ -23,7 +23,6 @@ typedef enum { STATUSTYPE_INFO, STATUSTYPE_TABLE } status_type_t;
 union map_info {
 	void *ptr;
 	unsigned long long ll;
-	unsigned target_request_nr;
 };
 
 /*
@@ -193,20 +192,21 @@ struct dm_target {
 	 * A number of zero-length barrier requests that will be submitted
 	 * to the target for the purpose of flushing cache.
 	 *
-	 * The request number will be placed in union map_info->target_request_nr.
+	 * The request number can be accessed with dm_bio_get_target_request_nr.
 	 * It is a responsibility of the target driver to remap these requests
 	 * to the real underlying devices.
 	 */
 	unsigned num_flush_requests;
 
 	/*
-	 * The number of discard requests that will be submitted to the
-	 * target.  map_info->request_nr is used just like num_flush_requests.
+	 * The number of discard requests that will be submitted to the target.
+	 * The request number can be accessed with dm_bio_get_target_request_nr.
 	 */
 	unsigned num_discard_requests;
 
 	/*
 	 * The number of WRITE SAME requests that will be submitted to the target.
+	 * The request number can be accessed with dm_bio_get_target_request_nr.
 	 */
 	unsigned num_write_same_requests;
 
@@ -263,6 +263,7 @@ struct dm_target_io {
 	struct dm_io *io;
 	struct dm_target *ti;
 	union map_info info;
+	unsigned target_request_nr;
 	struct bio clone;
 };
 
@@ -276,6 +277,11 @@ static inline struct bio *dm_bio_from_per_bio_data(void *data, size_t data_size)
 	return (struct bio *)((char *)data + data_size + offsetof(struct dm_target_io, clone));
 }
 
+static inline unsigned dm_bio_get_target_request_nr(const struct bio *bio)
+{
+	return container_of(bio, struct dm_target_io, clone)->target_request_nr;
+}
+
 int dm_register_target(struct target_type *t);
 void dm_unregister_target(struct target_type *t);