blk-cgroup: delete cpd_bind_fn of blkcg_policy

cpd_bind_fn is just used for update default weight when block
subsys attached to a hierarchy. No any policy need it anymore.
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20230406145050.49914-3-zhouchengming@bytedance.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-cgroup.c

@@ -1355,26 +1355,6 @@ void blkcg_exit_disk(struct gendisk *disk)
 	blk_throtl_exit(disk);
 }
 
-static void blkcg_bind(struct cgroup_subsys_state *root_css)
-{
-	int i;
-
-	mutex_lock(&blkcg_pol_mutex);
-
-	for (i = 0; i < BLKCG_MAX_POLS; i++) {
-		struct blkcg_policy *pol = blkcg_policy[i];
-		struct blkcg *blkcg;
-
-		if (!pol || !pol->cpd_bind_fn)
-			continue;
-
-		list_for_each_entry(blkcg, &all_blkcgs, all_blkcgs_node)
-			if (blkcg->cpd[pol->plid])
-				pol->cpd_bind_fn(blkcg->cpd[pol->plid]);
-	}
-	mutex_unlock(&blkcg_pol_mutex);
-}
-
 static void blkcg_exit(struct task_struct *tsk)
 {
 	if (tsk->throttle_disk)
@@ -1388,7 +1368,6 @@ struct cgroup_subsys io_cgrp_subsys = {
 	.css_offline = blkcg_css_offline,
 	.css_free = blkcg_css_free,
 	.css_rstat_flush = blkcg_rstat_flush,
-	.bind = blkcg_bind,
 	.dfl_cftypes = blkcg_files,
 	.legacy_cftypes = blkcg_legacy_files,
 	.legacy_name = "blkio",

block/blk-cgroup.h

@@ -175,7 +175,6 @@ struct blkcg_policy {
 	blkcg_pol_alloc_cpd_fn		*cpd_alloc_fn;
 	blkcg_pol_init_cpd_fn		*cpd_init_fn;
 	blkcg_pol_free_cpd_fn		*cpd_free_fn;
-	blkcg_pol_bind_cpd_fn		*cpd_bind_fn;
 
 	blkcg_pol_alloc_pd_fn		*pd_alloc_fn;
 	blkcg_pol_init_pd_fn		*pd_init_fn;