Re: [PATCH v2] arm64: mm: reserve hugetlb CMA after numa_init

From: Will Deacon
Date: Wed Jun 17 2020 - 06:18:32 EST


On Wed, Jun 17, 2020 at 10:19:24AM +1200, Barry Song wrote:
> hugetlb_cma_reserve() is called at the wrong place. numa_init has not been
> done yet. so all reserved memory will be located at node0.
>
> Fixes: cf11e85fc08c ("mm: hugetlb: optionally allocate gigantic hugepages using cma")

Damn, wasn't CC'd on that :/

> Cc: Matthias Brugger <matthias.bgg@xxxxxxxxx>
> Acked-by: Roman Gushchin <guro@xxxxxx>
> Signed-off-by: Barry Song <song.bao.hua@xxxxxxxxxxxxx>
> ---
> -v2: add Fixes tag according to Matthias Brugger's comment
>
> arch/arm64/mm/init.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index e631e6425165..41914b483d54 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -404,11 +404,6 @@ void __init arm64_memblock_init(void)
> high_memory = __va(memblock_end_of_DRAM() - 1) + 1;
>
> dma_contiguous_reserve(arm64_dma32_phys_limit);
> -
> -#ifdef CONFIG_ARM64_4K_PAGES
> - hugetlb_cma_reserve(PUD_SHIFT - PAGE_SHIFT);
> -#endif

Why is this dependent on CONFIG_ARM64_4K_PAGES? We unconditionally
select ARCH_HAS_GIGANTIC_PAGE so this seems unnecessary.

> -
> }
>
> void __init bootmem_init(void)
> @@ -424,6 +419,11 @@ void __init bootmem_init(void)
> min_low_pfn = min;
>
> arm64_numa_init();
> +
> +#ifdef CONFIG_ARM64_4K_PAGES
> + hugetlb_cma_reserve(PUD_SHIFT - PAGE_SHIFT);
> +#endif

A comment here wouldn't hurt, as it does look a lot more natural next
to dma_contiguous_reserve().

Will