Re: [PATCH 1/3] memcg/hugetlb: Introduce memcg_accounts_hugetlb

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

On Fri, Nov 08, 2024 at 01:29:44PM -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-off-by: Joshua Hahn <joshua.hahnjy@gmail.com>
> 
> ---
>  mm/memcontrol.c | 17 ++++++++++++++---
>  1 file changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index f3a9653cef0e..97f63ec9c9fb 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1425,6 +1425,9 @@ unsigned long memcg_page_state_local_output(struct mem_cgroup *memcg, int item)
>  		memcg_page_state_output_unit(item);
>  }
>  
> +/* Forward declaration */
> +bool memcg_accounts_hugetlb(void);

No need for forward declaration. Just define it here and make it static.

> +
>  static void memcg_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
>  {
>  	int i;
> @@ -1446,7 +1449,7 @@ static void memcg_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
>  
>  #ifdef CONFIG_HUGETLB_PAGE
>  		if (unlikely(memory_stats[i].idx == NR_HUGETLB) &&
> -		    !(cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING))
> +			!memcg_accounts_hugetlb())
>  			continue;
>  #endif
>  		size = memcg_page_state_output(memcg, memory_stats[i].idx);
> @@ -4483,6 +4486,15 @@ int __mem_cgroup_charge(struct folio *folio, struct mm_struct *mm, gfp_t gfp)
>  	return ret;
>  }
>  
> +bool memcg_accounts_hugetlb(void)
> +{
> +#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.
> @@ -4508,8 +4520,7 @@ 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))
> +		!cgroup_subsys_on_dfl(memory_cgrp_subsys) || !memcg_accounts_hugetlb())
>  		return -EOPNOTSUPP;
>  
>  	if (try_charge(memcg, gfp, nr_pages))
> -- 
> 2.43.5
>