Re: [PATCH 1/2] memcg/hugetlb: Introduce memcg_accounts_hugetlb

[Shakeel Butt <shakeel.butt@linux.dev>]

On Wed, Nov 06, 2024 at 02:14:33PM -0800, Joshua Hahn wrote:
> This patch isolates the check for whether memcg accounts hugetlb.
> This condition can only be true if the memcg mount option
> memory_hugetlb_accounting is on, which includes hugetlb usage
> in memory.current.
> 
> Signed-of-by: Joshua Hahn <joshua.hahnjy@gmail.com>
> 
> ---
>  include/linux/memcontrol.h |  2 ++
>  mm/memcontrol.c            | 12 ++++++++++--
>  2 files changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 34d2da05f2f1..25761d55799e 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -694,6 +694,8 @@ static inline int mem_cgroup_charge(struct folio *folio, struct mm_struct *mm,
>  	return __mem_cgroup_charge(folio, mm, gfp);
>  }
>  
> +bool memcg_accounts_hugetlb(void);
> +
>  int mem_cgroup_hugetlb_try_charge(struct mem_cgroup *memcg, gfp_t gfp,
>  		long nr_pages);
>  
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 5444d0e7bb64..59dea0122579 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -4497,6 +4497,15 @@ int __mem_cgroup_charge(struct folio *folio, struct mm_struct *mm, gfp_t gfp)
>  	return ret;
>  }
>  
> +bool memcg_accounts_hugetlb(void)

If this is only used in memcontrol.c then no need to add in the header,
just make it static here.

> +{
> +#ifdef CONFIG_HUGETLB_PAGE
> +	return cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING;
> +#else
> +	return false;
> +#endif
> +}
> +
>  /**
>   * mem_cgroup_hugetlb_try_charge - try to charge the memcg for a hugetlb folio
>   * @memcg: memcg to charge.
> @@ -4522,8 +4531,7 @@ int mem_cgroup_hugetlb_try_charge(struct mem_cgroup *memcg, gfp_t gfp,
>  	 * but do not attempt to commit charge later (or cancel on error) either.
>  	 */
>  	if (mem_cgroup_disabled() || !memcg ||
> -		!cgroup_subsys_on_dfl(memory_cgrp_subsys) ||
> -		!(cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING))

Why not replace in mem_cgroup_hugetlb_try_charge() as well?

> +		!cgroup_subsys_on_dfl(memory_cgrp_subsys) || !memcg_accounts_hugetlb())
>  		return -EOPNOTSUPP;
>  
>  	if (try_charge(memcg, gfp, nr_pages))
> -- 
> 2.43.5
>