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@xxxxxxxxxxx> Index: working-2.6/mm/memory.c =================================================================== --- working-2.6.orig/mm/memory.c 2006-02-24 11:44:36.000000000 +1100 +++ working-2.6/mm/memory.c 2006-03-02 11:14:03.000000000 +1100 @@ -277,7 +277,7 @@ void free_pgtables(struct mmu_gather **t 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 **t * 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); Index: working-2.6/include/asm-ia64/page.h =================================================================== --- working-2.6.orig/include/asm-ia64/page.h 2006-03-02 11:12:40.000000000 +1100 +++ working-2.6/include/asm-ia64/page.h 2006-03-02 11:30:26.000000000 +1100 @@ -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__ Index: working-2.6/include/asm-powerpc/pgtable.h =================================================================== --- working-2.6.orig/include/asm-powerpc/pgtable.h 2006-02-24 11:44:35.000000000 +1100 +++ working-2.6/include/asm-powerpc/pgtable.h 2006-03-02 11:29:26.000000000 +1100 @@ -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. Index: working-2.6/include/linux/hugetlb.h =================================================================== --- working-2.6.orig/include/linux/hugetlb.h 2006-03-02 11:12:40.000000000 +1100 +++ working-2.6/include/linux/hugetlb.h 2006-03-02 11:47:30.000000000 +1100 @@ -43,8 +43,10 @@ void hugetlb_change_protection(struct vm #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_tota #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) -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson - : send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
![]() |