pmd_present() checks _PAGE_PSE along with _PAGE_PRESENT to avoid false negative return when it races with thp spilt (during which _PAGE_PRESENT is temporary cleared.) I don't think that dropping _PAGE_PSE check in pmd_present() works well because it can hurt optimization of tlb handling in thp split. In the current kernel, bit 6 is not used in non-present format because nonlinear file mapping is obsolete, so let's move _PAGE_SWP_SOFT_DIRTY to that bit. Bit 7 is used as reserved (always clear), so please don't use it for other purpose. Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> --- arch/x86/include/asm/pgtable_types.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git v4.9-rc2-mmotm-2016-10-27-18-27/arch/x86/include/asm/pgtable_types.h v4.9-rc2-mmotm-2016-10-27-18-27_patched/arch/x86/include/asm/pgtable_types.h index 8b4de22..89e88f1 100644 --- v4.9-rc2-mmotm-2016-10-27-18-27/arch/x86/include/asm/pgtable_types.h +++ v4.9-rc2-mmotm-2016-10-27-18-27_patched/arch/x86/include/asm/pgtable_types.h @@ -98,14 +98,14 @@ * Tracking soft dirty bit when a page goes to a swap is tricky. * We need a bit which can be stored in pte _and_ not conflict * with swap entry format. On x86 bits 6 and 7 are *not* involved - * into swap entry computation, but bit 6 is used for nonlinear - * file mapping, so we borrow bit 7 for soft dirty tracking. + * into swap entry computation, but bit 7 is used for thp migration, + * so we borrow bit 6 for soft dirty tracking. * * Please note that this bit must be treated as swap dirty page - * mark if and only if the PTE has present bit clear! + * mark if and only if the PTE/PMD has present bit clear! */ #ifdef CONFIG_MEM_SOFT_DIRTY -#define _PAGE_SWP_SOFT_DIRTY _PAGE_PSE +#define _PAGE_SWP_SOFT_DIRTY _PAGE_DIRTY #else #define _PAGE_SWP_SOFT_DIRTY (_AT(pteval_t, 0)) #endif -- 2.7.0 -- 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>