linux-kernel - Re: [PATCH v3] mm/hugetlb: avoid hardcoding while checking if cma is enable

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Date:   Tue, 7 Jul 2020 11:18:11 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     Barry Song <song.bao.hua@...ilicon.com>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linuxarm@...wei.com,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Jonathan Cameron <jonathan.cameron@...wei.com>,
        Roman Gushchin <guro@...com>
Subject: Re: [PATCH v3] mm/hugetlb: avoid hardcoding while checking if cma is
 enable

On Tue, Jul 07, 2020 at 04:02:04PM +1200, Barry Song wrote:
> hugetlb_cma[0] can be NULL due to various reasons, for example, node0 has
> no memory. so NULL hugetlb_cma[0] doesn't necessarily mean cma is not
> enabled. gigantic pages might have been reserved on other nodes.
> 
> Fixes: cf11e85fc08c ("mm: hugetlb: optionally allocate gigantic hugepages using cma")
> Cc: Mike Kravetz <mike.kravetz@...cle.com>
> Cc: Jonathan Cameron <jonathan.cameron@...wei.com>
> Acked-by: Roman Gushchin <guro@...com>
> Signed-off-by: Barry Song <song.bao.hua@...ilicon.com>

Acked-by: Mike Rapoport <rppt@...ux.ibm.com>

> ---
>  -v3: add acked-by; make code more canonical 
> 
>  mm/hugetlb.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 57ece74e3aae..d293c823121e 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -2546,6 +2546,20 @@ static void __init gather_bootmem_prealloc(void)
>  	}
>  }
>  
> +bool __init hugetlb_cma_enabled(void)
> +{
> +#ifdef CONFIG_CMA
> +	int node;
> +
> +	for_each_online_node(node) {
> +		if (hugetlb_cma[node])
> +			return true;
> +	}
> +#endif
> +
> +	return false;
> +}
> +
>  static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
>  {
>  	unsigned long i;
> @@ -2571,7 +2585,7 @@ static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
>  
>  	for (i = 0; i < h->max_huge_pages; ++i) {
>  		if (hstate_is_gigantic(h)) {
> -			if (IS_ENABLED(CONFIG_CMA) && hugetlb_cma[0]) {
> +			if (hugetlb_cma_enabled()) {
>  				pr_warn_once("HugeTLB: hugetlb_cma is enabled, skip boot time allocation\n");
>  				break;
>  			}
> -- 
> 2.27.0
> 
> 
> 

-- 
Sincerely yours,
Mike.