We would want to use number of page table level to define mm_struct. Let's expose it as CONFIG_PGTABLE_LEVELS. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Russell King <linux@xxxxxxxxxxxxxxxx> Tested-by: Guenter Roeck <linux@xxxxxxxxxxxx> --- I've implemented accounting for pmd page tables as we have for pte (see mm->nr_ptes). It's requires a new counter in mm_struct: mm->nr_pmds. But the feature doesn't make any sense if an architecture has PMD level folded and it would be nice get rid of the counter in this case. The problem is that we cannot use __PAGETABLE_PMD_FOLDED in <linux/mm_types.h> due to circular dependencies: <linux/mm_types> -> <asm/pgtable.h> -> <linux/mm_types.h> In most cases <asm/pgtable.h> wants <linux/mm_types.h> to get definition of struct page and struct vm_area_struct. I've tried to split mm_struct into separate header file to be able to user <asm/pgtable.h> there. But it doesn't fly on some architectures, like ARM: it wants mm_struct <asm/pgtable.h> to implement tlb flushing. I don't see how to fix it without massive de-inlining or coverting a lot for inline functions to macros. This is other approach: expose number of page tables in use via Kconfig and use it in <linux/mm_types.h> instead of __PAGETABLE_PMD_FOLDED from <asm/pgtable.h>. --- arch/arm/Kconfig | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 9f1f09a2bc9b..16f20b2b37e3 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -286,6 +286,11 @@ config GENERIC_BUG def_bool y depends on BUG +config PGTABLE_LEVELS + int + default 3 if ARM_LPAE + default 2 + source "init/Kconfig" source "kernel/Kconfig.freezer" -- 2.1.4 -- 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>