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

[Muchun Song <muchun.song@linux.dev>]

> 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
>