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[PATCH v2] blk-cgroup: improve policy registration error handling

Chen Linxuan posted 1 patch 10 months, 1 week ago
There is a newer version of this series
block/blk-cgroup.c | 22 ++++++++++++----------
1 file changed, 12 insertions(+), 10 deletions(-)
[PATCH v2] blk-cgroup: improve policy registration error handling
Posted by Chen Linxuan 10 months, 1 week ago 
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>
---

v1->v2: Also change the return value to -ENOMEM from error path err_free_cpds

---
 block/blk-cgroup.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 9ed93d91d754..2609f7294427 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -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;
-- 
2.43.0
Re: [PATCH v2] blk-cgroup: improve policy registration error handling
Posted by Yu Kuai 10 months, 1 week ago 
在 2025/02/13 11:35, Chen Linxuan 写道:
> 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>
> ---
> 
> v1->v2: Also change the return value to -ENOMEM from error path err_free_cpds
> 
> ---
>   block/blk-cgroup.c | 22 ++++++++++++----------
>   1 file changed, 12 insertions(+), 10 deletions(-)
>
LGTM
Reviewed-by: Yu Kuai <yukuai3@huawei.com>

> diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
> index 9ed93d91d754..2609f7294427 100644
> --- a/block/blk-cgroup.c
> +++ b/block/blk-cgroup.c
> @@ -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;
>

Patchew 2.1-devel-b67e4c2

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