[PATCH v3 1/2] mm/cma: provide option to opt out from exposing pages on activation failure

[Hari Bathini]

Hi Andrew,

Could you please pick these patches via -mm tree.


On 17/01/22 1:22 pm, Hari Bathini wrote:
> Commit 072355c1cf2d ("mm/cma: expose all pages to the buddy if
> activation of an area fails") started exposing all pages to buddy
> allocator on CMA activation failure. But there can be CMA users that
> want to handle the reserved memory differently on CMA allocation
> failure. Provide an option to opt out from exposing pages to buddy
> for such cases.
> 
> Signed-off-by: Hari Bathini <hbathini at linux.ibm.com>
> Reviewed-by: David Hildenbrand <david at redhat.com>
> ---
> 
> Changes in v3:
> * Dropped NULL check in cma_reserve_pages_on_error().
> * Dropped explicit initialization of cma->reserve_pages_on_error to
>    'false' in cma_init_reserved_mem().
> * Added Reviewed-by tag from David.
> 
> Changes in v2:
> * Changed cma->free_pages_on_error to cma->reserve_pages_on_error and
>    cma_dont_free_pages_on_error() to cma_reserve_pages_on_error() to
>    avoid confusion.
> 
> 
>   include/linux/cma.h |  2 ++
>   mm/cma.c            | 11 +++++++++--
>   mm/cma.h            |  1 +
>   3 files changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/cma.h b/include/linux/cma.h
> index bd801023504b..51d540eee18a 100644
> --- a/include/linux/cma.h
> +++ b/include/linux/cma.h
> @@ -50,4 +50,6 @@ extern bool cma_pages_valid(struct cma *cma, const struct page *pages, unsigned
>   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);
> +
> +extern void cma_reserve_pages_on_error(struct cma *cma);
>   #endif
> diff --git a/mm/cma.c b/mm/cma.c
> index bc9ca8f3c487..766f1b82b532 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -131,8 +131,10 @@ static void __init cma_activate_area(struct cma *cma)
>   	bitmap_free(cma->bitmap);
>   out_error:
>   	/* Expose all pages to the buddy, they are useless for CMA. */
> -	for (pfn = base_pfn; pfn < base_pfn + cma->count; pfn++)
> -		free_reserved_page(pfn_to_page(pfn));
> +	if (!cma->reserve_pages_on_error) {
> +		for (pfn = base_pfn; pfn < base_pfn + cma->count; pfn++)
> +			free_reserved_page(pfn_to_page(pfn));
> +	}
>   	totalcma_pages -= cma->count;
>   	cma->count = 0;
>   	pr_err("CMA area %s could not be activated\n", cma->name);
> @@ -150,6 +152,11 @@ static int __init cma_init_reserved_areas(void)
>   }
>   core_initcall(cma_init_reserved_areas);
>   
> +void __init cma_reserve_pages_on_error(struct cma *cma)
> +{
> +	cma->reserve_pages_on_error = true;
> +}
> +
>   /**
>    * cma_init_reserved_mem() - create custom contiguous area from reserved memory
>    * @base: Base address of the reserved area
> diff --git a/mm/cma.h b/mm/cma.h
> index 2c775877eae2..88a0595670b7 100644
> --- a/mm/cma.h
> +++ b/mm/cma.h
> @@ -30,6 +30,7 @@ struct cma {
>   	/* kobject requires dynamic object */
>   	struct cma_kobject *cma_kobj;
>   #endif
> +	bool reserve_pages_on_error;
>   };
>   
>   extern struct cma cma_areas[MAX_CMA_AREAS];

Thanks
Hari