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SubjectRe: [PATCH resend] mm/page_alloc: fix comment is __get_free_pages
On Mon 27-11-17 19:09:24, JianKang Chen wrote:
> From: Jiankang Chen <chenjiankang1@huawei.com>
>
> __get_free_pages will return an virtual address,
> but it is not just 32-bit address, for example a 64-bit system.
> And this comment really confuse new bigenner of mm.

s@bigenner@beginner@

Anyway, do we really need a bug on for this? Has this actually caught
any wrong usage? VM_BUG_ON tends to be enabled these days AFAIK and
panicking the kernel seems like an over-reaction. If there is a real
risk then why don't we simply mask __GFP_HIGHMEM off when calling
alloc_pages?

> reported-by: Hanjun Guo <guohanjun@huawei.com>
> Signed-off-by: Jiankang Chen <chenjiankang1@huawei.com>
> ---
> mm/page_alloc.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 77e4d3c..5a7c432 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -4240,7 +4240,7 @@ unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order)
> struct page *page;
>
> /*
> - * __get_free_pages() returns a 32-bit address, which cannot represent
> + * __get_free_pages() returns a virtual address, which cannot represent
> * a highmem page
> */
> VM_BUG_ON((gfp_mask & __GFP_HIGHMEM) != 0);
> --
> 1.7.12.4
>

--
Michal Hocko
SUSE Labs

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