Commit e1a0202c authored by Chen Linxuan's avatar Chen Linxuan Committed by Jens Axboe
Browse files

blk-cgroup: improve policy registration error handling 



This patch improve the returned error code of blkcg_policy_register().

1. Move the validation check for cpd/pd_alloc_fn and cpd/pd_free_fn
   function pairs to the start of blkcg_policy_register(). This ensures
   we immediately return -EINVAL if the function pairs are not correctly
   provided, rather than returning -ENOSPC after locking and unlocking
   mutexes unnecessarily.

   Those locks should not contention any problems, as error of policy
   registration is a super cold path.

2. Return -ENOMEM when cpd_alloc_fn() failed.

Co-authored-by: default avatarWen Tao <wentao@uniontech.com>
Signed-off-by: default avatarWen Tao <wentao@uniontech.com>
Signed-off-by: default avatarChen Linxuan <chenlinxuan@uniontech.com>
Reviewed-by: default avatarMichal Koutný <mkoutny@suse.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Reviewed-by: default avatarYu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/3E333A73B6B6DFC0+20250317022924.150907-1-chenlinxuan@uniontech.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 86947bdc

block/blk-cgroup.c

+12 −10
Original line number Diff line number Diff line
@@ -1727,27 +1727,27 @@ int blkcg_policy_register(struct blkcg_policy *pol) 
	struct blkcg *blkcg;

	int i, ret;



	/*

	 * Make sure cpd/pd_alloc_fn and cpd/pd_free_fn in pairs, and policy

	 * without pd_alloc_fn/pd_free_fn can't be activated.

	 */

	if ((!pol->cpd_alloc_fn ^ !pol->cpd_free_fn) ||

	    (!pol->pd_alloc_fn ^ !pol->pd_free_fn))

		return -EINVAL;



	mutex_lock(&blkcg_pol_register_mutex);

	mutex_lock(&blkcg_pol_mutex);



	/* find an empty slot */

	ret = -ENOSPC;

	for (i = 0; i < BLKCG_MAX_POLS; i++)

		if (!blkcg_policy[i])

			break;

	if (i >= BLKCG_MAX_POLS) {

		pr_warn("blkcg_policy_register: BLKCG_MAX_POLS too small\n");

		ret = -ENOSPC;

		goto err_unlock;

	}



	/*

	 * Make sure cpd/pd_alloc_fn and cpd/pd_free_fn in pairs, and policy

	 * without pd_alloc_fn/pd_free_fn can't be activated.

	 */

	if ((!pol->cpd_alloc_fn ^ !pol->cpd_free_fn) ||

	    (!pol->pd_alloc_fn ^ !pol->pd_free_fn))

		goto err_unlock;



	/* register @pol */

	pol->plid = i;

	blkcg_policy[pol->plid] = pol;
@@ -1758,8 +1758,10 @@ int blkcg_policy_register(struct blkcg_policy *pol) 
			struct blkcg_policy_data *cpd;



			cpd = pol->cpd_alloc_fn(GFP_KERNEL);

			if (!cpd)

			if (!cpd) {

				ret = -ENOMEM;

				goto err_free_cpds;

			}



			blkcg->cpd[pol->plid] = cpd;

			cpd->blkcg = blkcg;