Dan Williams <dan.j.williams@xxxxxxxxx> writes: > On Thu, Jun 21, 2018 at 8:55 PM Huang, Ying <ying.huang@xxxxxxxxx> wrote: >> >> From: Huang Ying <ying.huang@xxxxxxxxx> >> >> Previously, the PMD swap operations are only enabled for >> CONFIG_ARCH_ENABLE_THP_MIGRATION. Because they are only used by the >> THP migration support. We will support PMD swap mapping to the huge >> swap cluster and swapin the THP as a whole. That will be enabled via >> CONFIG_THP_SWAP and needs these PMD swap operations. So enable the >> PMD swap operations for CONFIG_THP_SWAP too. >> >> Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx> >> Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> >> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> >> Cc: Michal Hocko <mhocko@xxxxxxxx> >> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> >> Cc: Shaohua Li <shli@xxxxxxxxxx> >> Cc: Hugh Dickins <hughd@xxxxxxxxxx> >> Cc: Minchan Kim <minchan@xxxxxxxxxx> >> Cc: Rik van Riel <riel@xxxxxxxxxx> >> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> >> Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> >> Cc: Zi Yan <zi.yan@xxxxxxxxxxxxxx> >> Cc: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx> >> --- >> arch/x86/include/asm/pgtable.h | 2 +- >> include/asm-generic/pgtable.h | 2 +- >> include/linux/swapops.h | 44 ++++++++++++++++++++++-------------------- >> 3 files changed, 25 insertions(+), 23 deletions(-) >> >> diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h >> index 99ecde23c3ec..13bf58838daf 100644 >> --- a/arch/x86/include/asm/pgtable.h >> +++ b/arch/x86/include/asm/pgtable.h >> @@ -1224,7 +1224,7 @@ static inline pte_t pte_swp_clear_soft_dirty(pte_t pte) >> return pte_clear_flags(pte, _PAGE_SWP_SOFT_DIRTY); >> } >> >> -#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION >> +#if defined(CONFIG_ARCH_ENABLE_THP_MIGRATION) || defined(CONFIG_THP_SWAP) > > How about introducing a new config symbol representing the common > infrastructure between the two and have them select that symbol. The common infrastructure shared by two mechanisms is PMD swap entry. But I didn't find there are many places where the common infrastructure is used. So I think it may be over-engineering to introduce a new config symbol but use it for so few times. > Would that also allow us to clean up the usage of > CONFIG_ARCH_ENABLE_THP_MIGRATION in fs/proc/task_mmu.c? In other > words, what's the point of having nice ifdef'd alternatives in header > files when ifdefs are still showing up in C files, all of it should be > optionally determined by header files. Unfortunately, I think it is not a easy task to wrap all C code via #ifdef in header files. And it may be over-engineering to wrap them all. I guess this is why there are still some #ifdef in C files. Best Regards, Huang, Ying
