From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> Currently, HPAGE_PMD_* constans rely on PMD_SHIFT regardless of CONFIG_TRANSPARENT_HUGEPAGE. PMD_SHIFT is not defined everywhere (e.g. arm nommu case). It means we can't use anything like this in generic code: if (PageTransHuge(page)) zero_huge_user(page, 0, HPAGE_PMD_SIZE); else clear_highpage(page); For !THP case, PageTransHuge() is 0 and compiler can eliminate zero_huge_user() call. But it still need to be valid C expression, means HPAGE_PMD_SIZE has to expand to something compiler can understand. Previously, HPAGE_PMD_* were defined to BUILD_BUG() for !THP. Let's come back to it. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> --- include/linux/huge_mm.h | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index cc276d2..e2dbefb 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -58,11 +58,12 @@ extern pmd_t *page_check_address_pmd(struct page *page, #define HPAGE_PMD_ORDER (HPAGE_PMD_SHIFT-PAGE_SHIFT) #define HPAGE_PMD_NR (1<<HPAGE_PMD_ORDER) + +#ifdef CONFIG_TRANSPARENT_HUGEPAGE #define HPAGE_PMD_SHIFT PMD_SHIFT #define HPAGE_PMD_SIZE ((1UL) << HPAGE_PMD_SHIFT) #define HPAGE_PMD_MASK (~(HPAGE_PMD_SIZE - 1)) -#ifdef CONFIG_TRANSPARENT_HUGEPAGE extern bool is_vma_temporary_stack(struct vm_area_struct *vma); #define transparent_hugepage_enabled(__vma) \ @@ -180,6 +181,9 @@ extern int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vm unsigned long addr, pmd_t pmd, pmd_t *pmdp); #else /* CONFIG_TRANSPARENT_HUGEPAGE */ +#define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; }) +#define HPAGE_PMD_MASK ({ BUILD_BUG(); 0; }) +#define HPAGE_PMD_SIZE ({ BUILD_BUG(); 0; }) #define hpage_nr_pages(x) 1 -- 1.8.3.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>