dm-raid1: don't use map_info

Don't use map_info.

map_info was used for writes to hold the region number (for this purpose
we add a new field dm_bio_details to dm_raid1_bio_record).

map_info was used for reads to hold a pointer to dm_raid1_bio_record (if
the pointer was non-NULL, bio details were saved; if the pointer was
NULL, bio details were not saved). We use
dm_raid1_bio_record.details->bi_bdev for this purpose. If bi_bdev is
NULL, details were not saved, if bi_bdev is non-NULL, details were
saved.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

Index: linux-3.6.6-fast/drivers/md/dm-raid1.c
===================================================================
--- linux-3.6.6-fast.orig/drivers/md/dm-raid1.c	2012-11-15 01:09:36.000000000 +0100
+++ linux-3.6.6-fast/drivers/md/dm-raid1.c	2012-11-15 01:09:38.000000000 +0100
@@ -143,7 +143,9 @@ static void dispatch_bios(void *context,
 
 struct dm_raid1_bio_record {
 	struct mirror *m;
+	/* if details->bi_bdev == NULL, details were not saved */
 	struct dm_bio_details details;
+	region_t write_region;
 };
 
 /*
@@ -1143,18 +1145,21 @@ static void mirror_dtr(struct dm_target 
 /*
  * Mirror mapping function
  */
-static int mirror_map(struct dm_target *ti, struct bio *bio,
-		      union map_info *map_context)
+static int mirror_map(struct dm_target *ti, struct bio *bio,
+		      union map_info *map_context)
 {
 	int r, rw = bio_rw(bio);
 	struct mirror *m;
 	struct mirror_set *ms = ti->private;
-	struct dm_raid1_bio_record *bio_record;
 	struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
+	struct dm_raid1_bio_record *bio_record =
+	  dm_bio_get_per_request_data(bio, sizeof(struct dm_raid1_bio_record));
+
+	bio_record->details.bi_bdev = NULL;
 
 	if (rw == WRITE) {
 		/* Save region for mirror_end_io() handler */
-		map_context->ll = dm_rh_bio_to_region(ms->rh, bio);
+		bio_record->write_region = dm_rh_bio_to_region(ms->rh, bio);
 		queue_bio(ms, bio, rw);
 		return DM_MAPIO_SUBMITTED;
 	}
@@ -1182,9 +1186,7 @@ static int mirror_map(struct dm_target *
 	if (unlikely(!m))
 		return -EIO;
 
-	bio_record = dm_bio_get_per_request_data(bio, sizeof(struct dm_raid1_bio_record));
 	dm_bio_record(&bio_record->details, bio);
-	map_context->ptr = bio_record;
 	bio_record->m = m;
 
 	map_bio(m, bio);
@@ -1192,21 +1194,22 @@ static int mirror_map(struct dm_target *
 	return DM_MAPIO_REMAPPED;
 }
 
-static int mirror_end_io(struct dm_target *ti, struct bio *bio,
-			 int error, union map_info *map_context)
+static int mirror_end_io(struct dm_target *ti, struct bio *bio,
+			 int error, union map_info *map_context)
 {
 	int rw = bio_rw(bio);
 	struct mirror_set *ms = (struct mirror_set *) ti->private;
 	struct mirror *m = NULL;
 	struct dm_bio_details *bd = NULL;
-	struct dm_raid1_bio_record *bio_record = map_context->ptr;
+	struct dm_raid1_bio_record *bio_record =
+	  dm_bio_get_per_request_data(bio, sizeof(struct dm_raid1_bio_record));
 
 	/*
 	 * We need to dec pending if this was a write.
 	 */
 	if (rw == WRITE) {
 		if (!(bio->bi_rw & (REQ_FLUSH | REQ_DISCARD)))
-			dm_rh_dec(ms->rh, map_context->ll);
+			dm_rh_dec(ms->rh, bio_record->write_region);
 		return error;
 	}
 
@@ -1217,7 +1219,7 @@ static int mirror_end_io(struct dm_targe
 		goto out;
 
 	if (unlikely(error)) {
-		if (!bio_record) {
+		if (!bio_record->details.bi_bdev) {
 			/*
 			 * There wasn't enough memory to record necessary
 			 * information for a retry or there was no other
@@ -1242,7 +1244,7 @@ static int mirror_end_io(struct dm_targe
 			bd = &bio_record->details;
 
 			dm_bio_restore(bd, bio);
-			map_context->ptr = NULL;
+			bio_record->details.bi_bdev = NULL;
 			queue_bio(ms, bio, rw);
 			return DM_ENDIO_INCOMPLETE;
 		}
@@ -1250,7 +1252,7 @@ static int mirror_end_io(struct dm_targe
 	}
 
 out:
-	map_context->ptr = NULL;
+	bio_record->details.bi_bdev = NULL;
 
 	return error;
 }