Re: [RFC PATCH 2/5] mm: shmem: add an 'order' parameter for shmem_alloc_hugefolio()

[Kefeng Wang <wangkefeng.wang@huawei.com>]

On 2024/4/22 15:02, Baolin Wang wrote:
> Add a new parameter to specify the huge page order for shmem_alloc_hugefolio(),
> as a preparation to supoort mTHP.
> 
> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
> ---
>   mm/shmem.c | 11 ++++++-----
>   1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/shmem.c b/mm/shmem.c
> index fa2a0ed97507..893c88efc45f 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1604,14 +1604,14 @@ static gfp_t limit_gfp_mask(gfp_t huge_gfp, gfp_t limit_gfp)
>   }
>   
>   static struct folio *shmem_alloc_hugefolio(gfp_t gfp,
> -		struct shmem_inode_info *info, pgoff_t index)
> +		struct shmem_inode_info *info, pgoff_t index, int order)
>   {
>   	struct mempolicy *mpol;
>   	pgoff_t ilx;
>   	struct page *page;
>   
> -	mpol = shmem_get_pgoff_policy(info, index, HPAGE_PMD_ORDER, &ilx);
> -	page = alloc_pages_mpol(gfp, HPAGE_PMD_ORDER, mpol, ilx, numa_node_id());
> +	mpol = shmem_get_pgoff_policy(info, index, order, &ilx);
> +	page = alloc_pages_mpol(gfp, order, mpol, ilx, numa_node_id());
>   	mpol_cond_put(mpol);
>   
>   	return page_rmappable_folio(page);
> @@ -1639,13 +1639,14 @@ static struct folio *shmem_alloc_and_add_folio(gfp_t gfp,
>   	struct shmem_inode_info *info = SHMEM_I(inode);
>   	struct folio *folio;
>   	long pages;
> -	int error;
> +	int error, order;
>   
>   	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
>   		huge = false;
>   
>   	if (huge) {
>   		pages = HPAGE_PMD_NR;
> +		order = HPAGE_PMD_ORDER;
>   		index = round_down(index, HPAGE_PMD_NR);
>   
>   		/*
> @@ -1660,7 +1661,7 @@ static struct folio *shmem_alloc_and_add_folio(gfp_t gfp,
>   				index + HPAGE_PMD_NR - 1, XA_PRESENT))
>   			return ERR_PTR(-E2BIG);
>   
> -		folio = shmem_alloc_hugefolio(gfp, info, index);
> +		folio = shmem_alloc_hugefolio(gfp, info, index, order);

Avoid order variable, we can directly use HPAGE_PMD_NR here.

>   		if (!folio)
>   			count_vm_event(THP_FILE_FALLBACK);
>   	} else {