6.14-stable review patch. If anyone has any objections, please let me know.
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From: Chen Linxuan chenlinxuan@uniontech.com
[ Upstream commit e1a0202c6bfda24002a3ae2115154fa90104c649 ]
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-chenlinxu... Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- 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 c94efae5bcfaf..8b07015db819a 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;