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SubjectRe: [PATCH v2 1/4] mm: change type of free_contig_range(nr_pages) to unsigned long
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On 05/04/2018 01:29 AM, Mike Kravetz wrote:
> free_contig_range() is currently defined as:
> void free_contig_range(unsigned long pfn, unsigned nr_pages);
> change to,
> void free_contig_range(unsigned long pfn, unsigned long nr_pages);
>
> Some callers are passing a truncated unsigned long today. It is
> highly unlikely that these values will overflow an unsigned int.
> However, this should be changed to an unsigned long to be consistent
> with other page counts.
>
> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
> ---
> include/linux/gfp.h | 2 +-
> mm/cma.c | 2 +-
> mm/hugetlb.c | 2 +-
> mm/page_alloc.c | 6 +++---
> 4 files changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index 1a4582b44d32..86a0d06463ab 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -572,7 +572,7 @@ static inline bool pm_suspended_storage(void)
> /* The below functions must be run on a range from a single zone. */
> extern int alloc_contig_range(unsigned long start, unsigned long end,
> unsigned migratetype, gfp_t gfp_mask);
> -extern void free_contig_range(unsigned long pfn, unsigned nr_pages);
> +extern void free_contig_range(unsigned long pfn, unsigned long nr_pages);
> #endif
>
> #ifdef CONFIG_CMA
> diff --git a/mm/cma.c b/mm/cma.c
> index aa40e6c7b042..f473fc2b7cbd 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -563,7 +563,7 @@ bool cma_release(struct cma *cma, const struct page *pages, unsigned int count)
>
> VM_BUG_ON(pfn + count > cma->base_pfn + cma->count);
>
> - free_contig_range(pfn, count);
> + free_contig_range(pfn, (unsigned long)count);

I guess this cast from uint to ulong doesn't need to be explicit? But
instead, cma_release() signature could be also changed to ulong, because
some of its callers do pass those?

> cma_clear_bitmap(cma, pfn, count);
> trace_cma_release(pfn, pages, count);
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 218679138255..c81072ce7510 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1055,7 +1055,7 @@ static void destroy_compound_gigantic_page(struct page *page,
>
> static void free_gigantic_page(struct page *page, unsigned int order)
> {
> - free_contig_range(page_to_pfn(page), 1 << order);
> + free_contig_range(page_to_pfn(page), 1UL << order);
> }
>
> static int __alloc_gigantic_page(unsigned long start_pfn,
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 905db9d7962f..0fd5e8e2456e 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -7937,9 +7937,9 @@ int alloc_contig_range(unsigned long start, unsigned long end,
> return ret;
> }
>
> -void free_contig_range(unsigned long pfn, unsigned nr_pages)
> +void free_contig_range(unsigned long pfn, unsigned long nr_pages)
> {
> - unsigned int count = 0;
> + unsigned long count = 0;
>
> for (; nr_pages--; pfn++) {
> struct page *page = pfn_to_page(pfn);
> @@ -7947,7 +7947,7 @@ void free_contig_range(unsigned long pfn, unsigned nr_pages)
> count += page_count(page) != 1;
> __free_page(page);
> }
> - WARN(count != 0, "%d pages are still in use!\n", count);
> + WARN(count != 0, "%ld pages are still in use!\n", count);

Maybe change to %lu while at it?
BTW, this warning can theoretically produce false positives, because
page users have to deal with page_count() being incremented by e.g.
parallel pfn scanners using get_page_unless_zero(). We also don't detect
refcount leaks in general. Should we remove it or change it to VM_WARN
if it's still useful for debugging?

> }
> #endif
>
>

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