Introduced by 
c6100a4b4e3d1 ("Btrfs: replace tree->mapping with
tree->private_data") to be used in run_one_async_done where it got
unused after 
736cd52e0c720103 ("Btrfs: remove nr_async_submits and
async_submit_draining").
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
 
  */
 struct async_submit_bio {
        void *private_data;
-       struct btrfs_fs_info *fs_info;
        struct bio *bio;
        extent_submit_bio_start_t *submit_bio_start;
        extent_submit_bio_done_t *submit_bio_done;
                return BLK_STS_RESOURCE;
 
        async->private_data = private_data;
-       async->fs_info = fs_info;
        async->bio = bio;
        async->mirror_num = mirror_num;
        async->submit_bio_start = submit_bio_start;