dm: move target_request_nr from map_info 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>

---
 drivers/md/dm-snap.c          |    2 +-
 drivers/md/dm-stripe.c        |    4 ++--
 drivers/md/dm.c               |    3 ++-
 include/linux/device-mapper.h |   13 +++++++++----
 4 files changed, 14 insertions(+), 8 deletions(-)

Index: linux-3.7-rc6/drivers/md/dm-snap.c
===================================================================
--- linux-3.7-rc6.orig/drivers/md/dm-snap.c	2012-11-17 21:31:55.000000000 +0100
+++ linux-3.7-rc6/drivers/md/dm-snap.c	2012-11-17 21:31:56.000000000 +0100
@@ -1685,7 +1685,7 @@ static int snapshot_merge_map(struct dm_
 	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;
Index: linux-3.7-rc6/drivers/md/dm-stripe.c
===================================================================
--- linux-3.7-rc6.orig/drivers/md/dm-stripe.c	2012-11-17 21:14:01.000000000 +0100
+++ linux-3.7-rc6/drivers/md/dm-stripe.c	2012-11-17 21:31:56.000000000 +0100
@@ -279,13 +279,13 @@ static int stripe_map(struct dm_target *
 	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);
 	}
Index: linux-3.7-rc6/drivers/md/dm.c
===================================================================
--- linux-3.7-rc6.orig/drivers/md/dm.c	2012-11-17 21:31:33.000000000 +0100
+++ linux-3.7-rc6/drivers/md/dm.c	2012-11-17 21:31:56.000000000 +0100
@@ -1121,6 +1121,7 @@ static struct dm_target_io *alloc_tio(st
 	tio->io = ci->io;
 	tio->ti = ti;
 	memset(&tio->info, 0, sizeof(tio->info));
+	tio->target_request_nr = 0;
 
 	return tio;
 }
@@ -1131,7 +1132,7 @@ static void __issue_target_request(struc
 	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.
Index: linux-3.7-rc6/include/linux/device-mapper.h
===================================================================
--- linux-3.7-rc6.orig/include/linux/device-mapper.h	2012-11-17 21:30:34.000000000 +0100
+++ linux-3.7-rc6/include/linux/device-mapper.h	2012-11-17 21:31:56.000000000 +0100
@@ -23,7 +23,6 @@ typedef enum { STATUSTYPE_INFO, STATUSTY
 union map_info {
 	void *ptr;
 	unsigned long long ll;
-	unsigned target_request_nr;
 };
 
 /*
@@ -193,15 +192,15 @@ 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;
 
@@ -258,6 +257,7 @@ struct dm_target_io {
 	struct dm_io *io;
 	struct dm_target *ti;
 	union map_info info;
+	unsigned target_request_nr;
 	struct bio clone;
 };
 
@@ -271,6 +271,11 @@ static inline struct bio *dm_per_request
 	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);