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@xxxxxxxxxxxxx>
Signed-off-by: Wen Tao <wentao@xxxxxxxxxxxxx>
Signed-off-by: Chen Linxuan <chenlinxuan@xxxxxxxxxxxxx>
---
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@xxxxxxxxxx>
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;
