[PATCH] hugepage: Fix hugepage logic in free_pgtables() (9da61aef) · Commits · 戴 / test

free_pgtables() has special logic to call hugetlb_free_pgd_range() instead of the normal free_pgd_range() on hugepage VMAs. However, the test it uses to do so is incorrect: it calls is_hugepage_only_range on a hugepage sized range at the start of the vma. is_hugepage_only_range() will return true if the given range has any intersection with a hugepage address region, and in this case the given region need not be hugepage aligned. So, for example, this test can return true if called on, say, a 4k VMA immediately preceding a (nicely aligned) hugepage VMA. At present we get away with this because the powerpc version of hugetlb_free_pgd_range() is just a call to free_pgd_range(). On ia64 (the only other arch with a non-trivial is_hugepage_only_range()) we get away with it for a different reason; the hugepage area is not contiguous with the rest of the user address space, and VMAs are not permitted in between, so the test can't return a false positive there. Nonetheless this should be fixed. We do that in the patch below by replacing the is_hugepage_only_range() test with an explicit test of the VMA using is_vm_hugetlb_page(). This in turn changes behaviour for platforms where is_hugepage_only_range() returns false always (everything except powerpc and ia64). We address this by ensuring that hugetlb_free_pgd_range() is defined to be identical to free_pgd_range() (instead of a no-op) on everything except ia64. Even so, it will prevent some otherwise possible coalescing of calls down to free_pgd_range(). Since this only happens for hugepage VMAs, removing this small optimization seems unlikely to cause any trouble. This patch causes no regressions on the libhugetlbfs testsuite - ppc64 POWER5 (8-way), ppc64 G5 (2-way) and i386 Pentium M (UP). Signed-off-by:

David Gibson <dwg@au1.ibm.com> Cc: William Lee Irwin III <wli@holomorphy.com> Acked-by:

Hugh Dickins <hugh@veritas.com> Signed-off-by:

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

Linus Torvalds <torvalds@osdl.org>

include/asm-ia64/page.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -57,6 +57,7 @@

		# define HAVE_ARCH_HUGETLB_UNMAPPED_AREA
		# define ARCH_HAS_HUGEPAGE_ONLY_RANGE
		# define ARCH_HAS_HUGETLB_FREE_PGD_RANGE
		#endif /* CONFIG_HUGETLB_PAGE */

		#ifdef __ASSEMBLY__

include/asm-powerpc/pgtable.h

+0 −5

Original line number	Diff line number	Diff line
		@@ -468,11 +468,6 @@ extern pgd_t swapper_pg_dir[];

		extern void paging_init(void);

		#ifdef CONFIG_HUGETLB_PAGE
		#define hugetlb_free_pgd_range(tlb, addr, end, floor, ceiling) \
		free_pgd_range(tlb, addr, end, floor, ceiling)
		#endif

		/*
		* This gets called at the end of handling a page fault, when
		* the kernel has put a new PTE into the page table for the process.

include/linux/hugetlb.h

+5 −4

Original line number	Diff line number	Diff line
		@@ -43,8 +43,10 @@ void hugetlb_change_protection(struct vm_area_struct *vma,

		#ifndef ARCH_HAS_HUGEPAGE_ONLY_RANGE
		#define is_hugepage_only_range(mm, addr, len) 0
		#define hugetlb_free_pgd_range(tlb, addr, end, floor, ceiling) \
		do { } while (0)
		#endif

		#ifndef ARCH_HAS_HUGETLB_FREE_PGD_RANGE
		#define hugetlb_free_pgd_range free_pgd_range
		#endif

		#ifndef ARCH_HAS_PREPARE_HUGEPAGE_RANGE
		@@ -93,8 +95,7 @@ static inline unsigned long hugetlb_total_pages(void)
		#define prepare_hugepage_range(addr, len) (-EINVAL)
		#define pmd_huge(x) 0
		#define is_hugepage_only_range(mm, addr, len) 0
		#define hugetlb_free_pgd_range(tlb, addr, end, floor, ceiling) \
		do { } while (0)
		#define hugetlb_free_pgd_range(tlb, addr, end, floor, ceiling) ({BUG(); 0; })
		#define hugetlb_fault(mm, vma, addr, write) ({ BUG(); 0; })

		#define hugetlb_change_protection(vma, address, end, newprot)

mm/memory.c

+2 −3

Original line number	Diff line number	Diff line
		@@ -277,7 +277,7 @@ void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct vma,
		anon_vma_unlink(vma);
		unlink_file_vma(vma);

		if (is_hugepage_only_range(vma->vm_mm, addr, HPAGE_SIZE)) {
		if (is_vm_hugetlb_page(vma)) {
		hugetlb_free_pgd_range(tlb, addr, vma->vm_end,
		floor, next? next->vm_start: ceiling);
		} else {
		@@ -285,8 +285,7 @@ void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct vma,
		* Optimization: gather nearby vmas into one call down
		*/
		while (next && next->vm_start <= vma->vm_end + PMD_SIZE
		&& !is_hugepage_only_range(vma->vm_mm, next->vm_start,
		HPAGE_SIZE)) {
		&& !is_vm_hugetlb_page(vma)) {
		vma = next;
		next = vma->vm_next;
		anon_vma_unlink(vma);

Admin message