btrfs: factor out block mapping for single profiles

Now that we have a container for the I/O geometry that has all the needed
information for the block mappings of SINGLE profiles, factor out a helper
calculating this information.

Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Author: morbidrsa

fs/btrfs/volumes.c

@@ -6484,6 +6484,14 @@ static void map_blocks_raid56_read(struct btrfs_chunk_map *map,
 		io_geom->mirror_num = 1;
 }
 
+static void map_blocks_single(const struct btrfs_chunk_map *map,
+			      struct btrfs_io_geometry *io_geom)
+{
+	io_geom->stripe_index = io_geom->stripe_nr % map->num_stripes;
+	io_geom->stripe_nr /= map->num_stripes;
+	io_geom->mirror_num = io_geom->stripe_index + 1;
+}
+
 /*
  * Map one logical range to one or more physical ranges.
  *
@@ -6586,9 +6594,7 @@ int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
 		 * device we have to walk to find the data, and stripe_index is
 		 * the number of our device in the stripe array
 		 */
-		io_geom.stripe_index = io_geom.stripe_nr % map->num_stripes;
-		io_geom.stripe_nr /= map->num_stripes;
-		io_geom.mirror_num = io_geom.stripe_index + 1;
+		map_blocks_single(map, &io_geom);
 	}
 	if (io_geom.stripe_index >= map->num_stripes) {
 		btrfs_crit(fs_info,