[PATCH 03/10] mm/hugetlb: Protect follow_huge_(pud|pgd) functions from race

[Anshuman Khandual]

On 04/07/2016 03:04 PM, kbuild test robot wrote:
> All errors (new ones prefixed by >>):
> 
>    mm/hugetlb.c: In function 'follow_huge_pud':
>>> >> mm/hugetlb.c:4360:3: error: implicit declaration of function 'pud_page' [-Werror=implicit-function-declaration]
>       page = pud_page(*pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT);
>       ^
>    mm/hugetlb.c:4360:8: warning: assignment makes pointer from integer without a cast
>       page = pud_page(*pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT);
>            ^
>    mm/hugetlb.c: In function 'follow_huge_pgd':
>    mm/hugetlb.c:4395:3: error: implicit declaration of function 'pgd_page' [-Werror=implicit-function-declaration]
>       page = pgd_page(*pgd) + ((address & ~PGDIR_MASK) >> PAGE_SHIFT);

Both the build errors here are because of the fact that pgd_page() is
not available for some platforms and config options. It got missed as
I ran only powerpc config options for build test purpose. My bad, will
fix it.