linux-kernel - Re: [PATCH v3 2/5] mm/cma: add cma_pages_valid to determine if pages are in CMA

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Date:   Tue, 5 Oct 2021 10:48:09 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     Michal Hocko <mhocko@...e.com>, Oscar Salvador <osalvador@...e.de>,
        Zi Yan <ziy@...dia.com>,
        Muchun Song <songmuchun@...edance.com>,
        Naoya Horiguchi <naoya.horiguchi@...ux.dev>,
        David Rientjes <rientjes@...gle.com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v3 2/5] mm/cma: add cma_pages_valid to determine if pages
 are in CMA

On 01.10.21 19:52, Mike Kravetz wrote:
> Add new interface cma_pages_valid() which indicates if the specified
> pages are part of a CMA region.  This interface will be used in a
> subsequent patch by hugetlb code.
> 
> Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
> ---
>   include/linux/cma.h |  1 +
>   mm/cma.c            | 21 +++++++++++++++++----
>   2 files changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/cma.h b/include/linux/cma.h
> index 53fd8c3cdbd0..bd801023504b 100644
> --- a/include/linux/cma.h
> +++ b/include/linux/cma.h
> @@ -46,6 +46,7 @@ extern int cma_init_reserved_mem(phys_addr_t base, phys_addr_t size,
>   					struct cma **res_cma);
>   extern struct page *cma_alloc(struct cma *cma, unsigned long count, unsigned int align,
>   			      bool no_warn);
> +extern bool cma_pages_valid(struct cma *cma, const struct page *pages, unsigned long count);
>   extern bool cma_release(struct cma *cma, const struct page *pages, unsigned long count);
>   
>   extern int cma_for_each_area(int (*it)(struct cma *cma, void *data), void *data);
> diff --git a/mm/cma.c b/mm/cma.c
> index 995e15480937..960994b88c7f 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -524,6 +524,22 @@ struct page *cma_alloc(struct cma *cma, unsigned long count,
>   	return page;
>   }
>   
> +bool cma_pages_valid(struct cma *cma, const struct page *pages,
> +		     unsigned long count)
> +{
> +	unsigned long pfn;
> +
> +	if (!cma || !pages)
> +		return false;
> +
> +	pfn = page_to_pfn(pages);
> +
> +	if (pfn < cma->base_pfn || pfn >= cma->base_pfn + cma->count)
> +		return false;
> +
> +	return true;
> +}
> +
>   /**
>    * cma_release() - release allocated pages
>    * @cma:   Contiguous memory region for which the allocation is performed.
> @@ -539,16 +555,13 @@ bool cma_release(struct cma *cma, const struct page *pages,
>   {
>   	unsigned long pfn;
>   
> -	if (!cma || !pages)
> +	if (!cma_pages_valid(cma, pages, count))
>   		return false;
>   
>   	pr_debug("%s(page %p, count %lu)\n", __func__, (void *)pages, count);
>   
>   	pfn = page_to_pfn(pages);
>   
> -	if (pfn < cma->base_pfn || pfn >= cma->base_pfn + cma->count)
> -		return false;
> -
>   	VM_BUG_ON(pfn + count > cma->base_pfn + cma->count);
>   
>   	free_contig_range(pfn, count);
> 

Agreed that we might want to perform the pr_debug() now earlier, or do 
another pr_warn before returning false.

Acked-by: David Hildenbrand <david@...hat.com>

-- 
Thanks,

David / dhildenb