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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: Wen Tao <wentao@uniontech.com>
Signed-off-by: Wen Tao <wentao@uniontech.com>
Signed-off-by: Chen Linxuan <chenlinxuan@uniontech.com>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/3E333A73B6B6DFC0+20250317022924.150907-1-chenlinxuan@uniontech.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
pull/1188/head
Chen Linxuan 2025-03-17 10:29:24 +08:00 committed by Jens Axboe
parent 86947bdc28
commit e1a0202c6b
1 changed files with 16 additions and 14 deletions
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30
block/blk-cgroup.c
View File

@ -1727,26 +1727,26 @@ int blkcg_policy_register(struct blkcg_policy *pol)
struct blkcg *blkcg; struct blkcg *blkcg;
int i, ret; int i, ret;
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");
goto err_unlock;
}
/* /*
* Make sure cpd/pd_alloc_fn and cpd/pd_free_fn in pairs, and policy * 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. * without pd_alloc_fn/pd_free_fn can't be activated.
*/ */
if ((!pol->cpd_alloc_fn ^ !pol->cpd_free_fn) || if ((!pol->cpd_alloc_fn ^ !pol->cpd_free_fn) ||
(!pol->pd_alloc_fn ^ !pol->pd_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 */
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; goto err_unlock;
}
/* register @pol */ /* register @pol */
pol->plid = i; pol->plid = i;
@ -1758,8 +1758,10 @@ int blkcg_policy_register(struct blkcg_policy *pol)
struct blkcg_policy_data *cpd; struct blkcg_policy_data *cpd;
cpd = pol->cpd_alloc_fn(GFP_KERNEL); cpd = pol->cpd_alloc_fn(GFP_KERNEL);
if (!cpd) if (!cpd) {
ret = -ENOMEM;
goto err_free_cpds; goto err_free_cpds;
}
blkcg->cpd[pol->plid] = cpd; blkcg->cpd[pol->plid] = cpd;
cpd->blkcg = blkcg; cpd->blkcg = blkcg;