linux-kernel - Re: [PATCH] mm/hugetlb: Move page order check inside hugetlb_cma

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Date: Thu, 8 Feb 2024 22:41:23 -0800
From: Jane Chu <jane.chu@...cle.com>
To: Anshuman Khandual <anshuman.khandual@....com>, linux-mm@...ck.org
Cc: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        linux-arm-kernel@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/hugetlb: Move page order check inside
 hugetlb_cma_reserve()

On 2/8/2024 9:42 PM, Anshuman Khandual wrote:

> All platforms could benefit from page order check against MAX_PAGE_ORDER
> before allocating a CMA area for gigantic hugetlb pages. Let's move this
> check from individual platforms to generic hugetlb.
>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Nicholas Piggin <npiggin@...il.com>
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linuxppc-dev@...ts.ozlabs.org
> Cc: linux-mm@...ck.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---
> This applies on v6.8-rc3
>   
>   arch/arm64/mm/hugetlbpage.c   | 7 -------
>   arch/powerpc/mm/hugetlbpage.c | 4 +---
>   mm/hugetlb.c                  | 7 +++++++
>   3 files changed, 8 insertions(+), 10 deletions(-)
>
> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
> index 8116ac599f80..6720ec8d50e7 100644
> --- a/arch/arm64/mm/hugetlbpage.c
> +++ b/arch/arm64/mm/hugetlbpage.c
> @@ -45,13 +45,6 @@ void __init arm64_hugetlb_cma_reserve(void)
>   	else
>   		order = CONT_PMD_SHIFT - PAGE_SHIFT;
>   
> -	/*
> -	 * HugeTLB CMA reservation is required for gigantic
> -	 * huge pages which could not be allocated via the
> -	 * page allocator. Just warn if there is any change
> -	 * breaking this assumption.
> -	 */
> -	WARN_ON(order <= MAX_PAGE_ORDER);
>   	hugetlb_cma_reserve(order);
>   }
>   #endif /* CONFIG_CMA */
> diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
> index 0a540b37aab6..16557d008eef 100644
> --- a/arch/powerpc/mm/hugetlbpage.c
> +++ b/arch/powerpc/mm/hugetlbpage.c
> @@ -614,8 +614,6 @@ void __init gigantic_hugetlb_cma_reserve(void)
>   		 */
>   		order = mmu_psize_to_shift(MMU_PAGE_16G) - PAGE_SHIFT;
>   
> -	if (order) {
> -		VM_WARN_ON(order <= MAX_PAGE_ORDER);
> +	if (order)
>   		hugetlb_cma_reserve(order);
> -	}
>   }
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index cf9c9b2906ea..345b3524df35 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -7699,6 +7699,13 @@ void __init hugetlb_cma_reserve(int order)
>   	bool node_specific_cma_alloc = false;
>   	int nid;
>   
> +	/*
> +	 * HugeTLB CMA reservation is required for gigantic
> +	 * huge pages which could not be allocated via the
> +	 * page allocator. Just warn if there is any change
> +	 * breaking this assumption.
> +	 */
> +	VM_WARN_ON(order <= MAX_PAGE_ORDER);
>   	cma_reserve_called = true;
>   
>   	if (!hugetlb_cma_size)

Looks straight forward to me.

Reviewed-by: Jane Chu <jane.chu@...cle.com>