mm/thp: define HPAGE_PMD_* constants as BUILD_BUG() if !THP (3766a1ab) · Commits · 戴 / test

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@linux.intel.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Benjamin Herrenschmidt <benh@kernel.crashing.org>

include/linux/huge_mm.h

+5 −1

Original line number	Original line	Diff line number	Diff line
	@@ -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_ORDER (HPAGE_PMD_SHIFT-PAGE_SHIFT)
	#define HPAGE_PMD_NR (1<<HPAGE_PMD_ORDER)		#define HPAGE_PMD_NR (1<<HPAGE_PMD_ORDER)

			#ifdef CONFIG_TRANSPARENT_HUGEPAGE
	#define HPAGE_PMD_SHIFT PMD_SHIFT		#define HPAGE_PMD_SHIFT PMD_SHIFT
	#define HPAGE_PMD_SIZE ((1UL) << HPAGE_PMD_SHIFT)		#define HPAGE_PMD_SIZE ((1UL) << HPAGE_PMD_SHIFT)
	#define HPAGE_PMD_MASK (~(HPAGE_PMD_SIZE - 1))		#define HPAGE_PMD_MASK (~(HPAGE_PMD_SIZE - 1))

	#ifdef CONFIG_TRANSPARENT_HUGEPAGE
	extern bool is_vma_temporary_stack(struct vm_area_struct *vma);		extern bool is_vma_temporary_stack(struct vm_area_struct *vma);

	#define transparent_hugepage_enabled(__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);		unsigned long addr, pmd_t pmd, pmd_t *pmdp);

	#else /* CONFIG_TRANSPARENT_HUGEPAGE */		#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		#define hpage_nr_pages(x) 1

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