Re: [PATCH v1] mm/shrinker: simplify shrinker_memcg_alloc() using guard()

[wangxuewen <18810879172@163.com>]

Hi,Muchun Song,

Thanks for your review.
I've updated the patch to v2 following your suggestions.

This change is only a local cleanup for this specific function, not part 
of any large-scale conversion to use the guard() mechanism.

Please review v2, thank you.

在 2026/5/12 17:10, Muchun Song 写道:
> 
> 
>> On May 12, 2026, at 16:55, wangxuewen <18810879172@163.com> wrote:
>>
>> Use guard(mutex) to automatically handle shrinker_mutex locking and
>> unlocking in shrinker_memcg_alloc(). This removes the explicit
>> mutex_unlock() call, the goto-based error path, and the redundant
>> ret variable, resulting in cleaner and more concise code.
>>
>> Signed-off-by: wangxuewen <wangxuewen@kylinos.cn>
>> ---
>> mm/shrinker.c | 11 ++++-------
>> 1 file changed, 4 insertions(+), 7 deletions(-)
>>
>> diff --git a/mm/shrinker.c b/mm/shrinker.c
>> index 76b3f750cf65..1274130323bf 100644
>> --- a/mm/shrinker.c
>> +++ b/mm/shrinker.c
>> @@ -222,22 +222,19 @@ static int shrinker_memcg_alloc(struct shrinker *shrinker)
>> if (mem_cgroup_kmem_disabled() && !(shrinker->flags & SHRINKER_NONSLAB))
>> return -ENOSYS;
>>
>> - 	mutex_lock(&shrinker_mutex);
>> + 	guard(mutex)(&shrinker_mutex);
>> 	id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL);
>> 	if (id < 0)
>> - 		goto unlock;
>> + 	return id;
>>
>> 	if (id >= shrinker_nr_max) {
>> 		if (expand_shrinker_info(id)) {
>> 			idr_remove(&shrinker_idr, id);
>> - 			goto unlock;
>> + 			return -ENOMEM;
>> 		}
>> 	}
>> 	shrinker->id = id;
>> - 	ret = 0;
>> -unlock:
>> - 	mutex_unlock(&shrinker_mutex);
>> - 	return ret;
> 
> One small thing: since ret is no longer used after this change,
> it should be dropped from the declaration to avoid an unused-variable
> warning:
> 
>      -       int id, ret = -ENOMEM;
>      +       int id;
> 
> Otherwise looks good to me.
> 
> Thanks,
> Muchun
> 
>> + 	return 0;
>> }
>>
>> static void shrinker_memcg_remove(struct shrinker *shrinker)
>> -- 
>> 2.25.1
>>