cgroup/blkio: Add deprecation messages to reset_stats

It is difficult to sync with stat updaters, stats are (should be)
monotonic so users can calculate differences from a reference.

Signed-off-by: Michal Koutný <[email protected]>
Acked-by: Jens Axboe <[email protected]>
Signed-off-by: Tejun Heo <[email protected]>

Author: Werkov

block/blk-cgroup.c

@@ -659,6 +659,7 @@ static int blkcg_reset_stats(struct cgroup_subsys_state *css,
 	struct blkcg_gq *blkg;
 	int i;
 
+	pr_info_once("blkio.%s is deprecated\n", cftype->name);
 	mutex_lock(&blkcg_pol_mutex);
 	spin_lock_irq(&blkcg->lock);