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    Subject[PATCH -V9 02/21] swap: Enable PMD swap operations for CONFIG_THP_SWAP
    Date
    Currently, "the swap entry" in the page tables is used for a number of
    things outside of actual swap, like page migration, etc. We support
    the THP/PMD "swap entry" for page migration currently and the
    functions behind this are tied to page migration's config
    option (CONFIG_ARCH_ENABLE_THP_MIGRATION).

    But, we also need them for THP swap optimization. So a new config
    option (CONFIG_HAVE_PMD_SWAP_ENTRY) is added. It is enabled when
    either CONFIG_ARCH_ENABLE_THP_MIGRATION or CONFIG_THP_SWAP is enabled.
    And PMD swap entry functions are tied to this new config option
    instead. Some functions enabled by CONFIG_ARCH_ENABLE_THP_MIGRATION
    are for page migration only, they are still enabled only for that.

    Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
    Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
    Cc: Andrea Arcangeli <aarcange@redhat.com>
    Cc: Michal Hocko <mhocko@kernel.org>
    Cc: Johannes Weiner <hannes@cmpxchg.org>
    Cc: Shaohua Li <shli@kernel.org>
    Cc: Hugh Dickins <hughd@google.com>
    Cc: Minchan Kim <minchan@kernel.org>
    Cc: Rik van Riel <riel@redhat.com>
    Cc: Dave Hansen <dave.hansen@linux.intel.com>
    Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
    Cc: Zi Yan <zi.yan@cs.rutgers.edu>
    Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
    ---
    arch/x86/include/asm/pgtable.h | 2 +-
    include/asm-generic/pgtable.h | 2 +-
    include/linux/swapops.h | 44 ++++++++++++++++++----------------
    mm/Kconfig | 8 +++++++
    4 files changed, 33 insertions(+), 23 deletions(-)

    diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
    index 40616e805292..e830ab345551 100644
    --- a/arch/x86/include/asm/pgtable.h
    +++ b/arch/x86/include/asm/pgtable.h
    @@ -1333,7 +1333,7 @@ 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
    +#ifdef CONFIG_HAVE_PMD_SWAP_ENTRY
    static inline pmd_t pmd_swp_mksoft_dirty(pmd_t pmd)
    {
    return pmd_set_flags(pmd, _PAGE_SWP_SOFT_DIRTY);
    diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
    index e0381a4ce7d4..2a619f378297 100644
    --- a/include/asm-generic/pgtable.h
    +++ b/include/asm-generic/pgtable.h
    @@ -675,7 +675,7 @@ static inline void ptep_modify_prot_commit(struct mm_struct *mm,
    #endif

    #ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY
    -#ifndef CONFIG_ARCH_ENABLE_THP_MIGRATION
    +#ifndef CONFIG_HAVE_PMD_SWAP_ENTRY
    static inline pmd_t pmd_swp_mksoft_dirty(pmd_t pmd)
    {
    return pmd;
    diff --git a/include/linux/swapops.h b/include/linux/swapops.h
    index 4d961668e5fc..905ddc65caa3 100644
    --- a/include/linux/swapops.h
    +++ b/include/linux/swapops.h
    @@ -254,17 +254,7 @@ static inline int is_write_migration_entry(swp_entry_t entry)

    #endif

    -struct page_vma_mapped_walk;
    -
    -#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
    -extern void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
    - struct page *page);
    -
    -extern void remove_migration_pmd(struct page_vma_mapped_walk *pvmw,
    - struct page *new);
    -
    -extern void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd);
    -
    +#ifdef CONFIG_HAVE_PMD_SWAP_ENTRY
    static inline swp_entry_t pmd_to_swp_entry(pmd_t pmd)
    {
    swp_entry_t arch_entry;
    @@ -282,6 +272,28 @@ static inline pmd_t swp_entry_to_pmd(swp_entry_t entry)
    arch_entry = __swp_entry(swp_type(entry), swp_offset(entry));
    return __swp_entry_to_pmd(arch_entry);
    }
    +#else
    +static inline swp_entry_t pmd_to_swp_entry(pmd_t pmd)
    +{
    + return swp_entry(0, 0);
    +}
    +
    +static inline pmd_t swp_entry_to_pmd(swp_entry_t entry)
    +{
    + return __pmd(0);
    +}
    +#endif
    +
    +struct page_vma_mapped_walk;
    +
    +#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
    +extern void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
    + struct page *page);
    +
    +extern void remove_migration_pmd(struct page_vma_mapped_walk *pvmw,
    + struct page *new);
    +
    +extern void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd);

    static inline int is_pmd_migration_entry(pmd_t pmd)
    {
    @@ -302,16 +314,6 @@ static inline void remove_migration_pmd(struct page_vma_mapped_walk *pvmw,

    static inline void pmd_migration_entry_wait(struct mm_struct *m, pmd_t *p) { }

    -static inline swp_entry_t pmd_to_swp_entry(pmd_t pmd)
    -{
    - return swp_entry(0, 0);
    -}
    -
    -static inline pmd_t swp_entry_to_pmd(swp_entry_t entry)
    -{
    - return __pmd(0);
    -}
    -
    static inline int is_pmd_migration_entry(pmd_t pmd)
    {
    return 0;
    diff --git a/mm/Kconfig b/mm/Kconfig
    index 25c71eb8a7db..d7c5299c5b7d 100644
    --- a/mm/Kconfig
    +++ b/mm/Kconfig
    @@ -422,6 +422,14 @@ config THP_SWAP

    For selection by architectures with reasonable THP sizes.

    +#
    +# "PMD swap entry" in the page table is used both for migration and
    +# actual swap.
    +#
    +config HAVE_PMD_SWAP_ENTRY
    + def_bool y
    + depends on THP_SWAP || ARCH_ENABLE_THP_MIGRATION
    +
    config TRANSPARENT_HUGE_PAGECACHE
    def_bool y
    depends on TRANSPARENT_HUGEPAGE
    --
    2.18.1
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