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    SubjectRe: [v3 PATCH 5/7] mm: thp: kill transparent_hugepage_active()
    On Mon, Jun 6, 2022 at 2:44 PM Yang Shi <shy828301@gmail.com> wrote:
    >
    > The transparent_hugepage_active() was introduced to show THP eligibility
    > bit in smaps in proc, smaps is the only user. But it actually does the
    > similar check as hugepage_vma_check() which is used by khugepaged. We
    > definitely don't have to maintain two similar checks, so kill
    > transparent_hugepage_active().

    I never realized smaps was the only user! Great!

    > Also move hugepage_vma_check() to huge_memory.c and huge_mm.h since it
    > is not only for khugepaged anymore.
    >
    > Signed-off-by: Yang Shi <shy828301@gmail.com>
    > ---
    > fs/proc/task_mmu.c | 2 +-
    > include/linux/huge_mm.h | 16 +++++++-----
    > include/linux/khugepaged.h | 4 +--
    > mm/huge_memory.c | 50 ++++++++++++++++++++++++++++++++-----
    > mm/khugepaged.c | 51 +++-----------------------------------
    > 5 files changed, 60 insertions(+), 63 deletions(-)
    >
    > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
    > index 2dd8c8a66924..fd79566e204c 100644
    > --- a/fs/proc/task_mmu.c
    > +++ b/fs/proc/task_mmu.c
    > @@ -860,7 +860,7 @@ static int show_smap(struct seq_file *m, void *v)
    > __show_smap(m, &mss, false);
    >
    > seq_printf(m, "THPeligible: %d\n",
    > - transparent_hugepage_active(vma));
    > + hugepage_vma_check(vma, vma->vm_flags, true));
    >
    > if (arch_pkeys_enabled())
    > seq_printf(m, "ProtectionKey: %8u\n", vma_pkey(vma));
    > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
    > index 79d5919beb83..f561c3e16def 100644
    > --- a/include/linux/huge_mm.h
    > +++ b/include/linux/huge_mm.h
    > @@ -209,7 +209,9 @@ static inline bool file_thp_enabled(struct vm_area_struct *vma)
    > !inode_is_open_for_write(inode) && S_ISREG(inode->i_mode);
    > }
    >
    > -bool transparent_hugepage_active(struct vm_area_struct *vma);
    > +bool hugepage_vma_check(struct vm_area_struct *vma,
    > + unsigned long vm_flags,
    > + bool smaps);
    >
    > #define transparent_hugepage_use_zero_page() \
    > (transparent_hugepage_flags & \
    > @@ -358,11 +360,6 @@ static inline bool __transparent_hugepage_enabled(struct vm_area_struct *vma)
    > return false;
    > }
    >
    > -static inline bool transparent_hugepage_active(struct vm_area_struct *vma)
    > -{
    > - return false;
    > -}
    > -
    > static inline bool transhuge_vma_size_ok(struct vm_area_struct *vma)
    > {
    > return false;
    > @@ -380,6 +377,13 @@ static inline bool transhuge_vma_enabled(struct vm_area_struct *vma,
    > return false;
    > }
    >
    > +static inline bool hugepage_vma_check(struct vm_area_struct *vma,
    > + unsigned long vm_flags,
    > + bool smaps)
    > +{
    > + return false;
    > +}
    > +
    > static inline void prep_transhuge_page(struct page *page) {}
    >
    > #define transparent_hugepage_flags 0UL
    > diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h
    > index 392d34c3c59a..8a6452e089ca 100644
    > --- a/include/linux/khugepaged.h
    > +++ b/include/linux/khugepaged.h
    > @@ -10,8 +10,6 @@ extern struct attribute_group khugepaged_attr_group;
    > extern int khugepaged_init(void);
    > extern void khugepaged_destroy(void);
    > extern int start_stop_khugepaged(void);
    > -extern bool hugepage_vma_check(struct vm_area_struct *vma,
    > - unsigned long vm_flags);
    > extern void __khugepaged_enter(struct mm_struct *mm);
    > extern void __khugepaged_exit(struct mm_struct *mm);
    > extern void khugepaged_enter_vma(struct vm_area_struct *vma,
    > @@ -57,7 +55,7 @@ static inline void khugepaged_enter(struct vm_area_struct *vma,
    > {
    > if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags) &&
    > khugepaged_enabled()) {
    > - if (hugepage_vma_check(vma, vm_flags))
    > + if (hugepage_vma_check(vma, vm_flags, false))
    > __khugepaged_enter(vma->vm_mm);
    > }
    > }
    > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
    > index 36ada544e494..bc8370856e85 100644
    > --- a/mm/huge_memory.c
    > +++ b/mm/huge_memory.c
    > @@ -69,18 +69,56 @@ static atomic_t huge_zero_refcount;
    > struct page *huge_zero_page __read_mostly;
    > unsigned long huge_zero_pfn __read_mostly = ~0UL;
    >
    > -bool transparent_hugepage_active(struct vm_area_struct *vma)
    > +bool hugepage_vma_check(struct vm_area_struct *vma,
    > + unsigned long vm_flags,
    > + bool smaps)
    > {
    > + if (!transhuge_vma_enabled(vma, vm_flags))
    > + return false;
    > +
    > + if (vm_flags & VM_NO_KHUGEPAGED)
    > + return false;
    > +
    > + /* Don't run khugepaged against DAX vma */
    > + if (vma_is_dax(vma))
    > + return false;
    > +
    > + if (vma->vm_file && !IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) -
    > + vma->vm_pgoff, HPAGE_PMD_NR))
    > + return false;
    > +
    > if (!transhuge_vma_size_ok(vma))
    > return false;
    > - if (vma_is_anonymous(vma))
    > - return __transparent_hugepage_enabled(vma);
    > - if (vma_is_shmem(vma))
    > +
    > + /* Enabled via shmem mount options or sysfs settings. */
    > + if (shmem_file(vma->vm_file))
    > return shmem_huge_enabled(vma);
    > - if (transhuge_vma_enabled(vma, vma->vm_flags) && file_thp_enabled(vma))
    > +
    > + if (!khugepaged_enabled())
    > + return false;
    > +
    > + /* THP settings require madvise. */
    > + if (!(vm_flags & VM_HUGEPAGE) && !khugepaged_always())
    > + return false;
    > +
    > + /* Only regular file is valid */
    > + if (file_thp_enabled(vma))
    > return true;
    >
    > - return false;
    > + if (!vma_is_anonymous(vma))
    > + return false;
    > +
    > + if (vma_is_temporary_stack(vma))
    > + return false;
    > +
    > + /*
    > + * THPeligible bit of smaps should show 1 for proper VMAs even
    > + * though anon_vma is not initialized yet.
    > + */
    > + if (!vma->anon_vma)
    > + return smaps;
    > +
    > + return true;
    > }

    There are a few cases where the return value for smaps will be
    different from before. I presume this won't be an issue, and that any
    difference resulting from this change is actually a positive
    difference, given it more accurately reflects the thp eligibility of
    the vma? For example, a VM_NO_KHUGEPAGED-marked vma might now show 0
    where it otherwise showed 1.

    > static bool get_huge_zero_page(void)
    > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
    > index ca1754d3a827..aa0769e3b0d9 100644
    > --- a/mm/khugepaged.c
    > +++ b/mm/khugepaged.c
    > @@ -437,49 +437,6 @@ static inline int khugepaged_test_exit(struct mm_struct *mm)
    > return atomic_read(&mm->mm_users) == 0;
    > }
    >
    > -bool hugepage_vma_check(struct vm_area_struct *vma,
    > - unsigned long vm_flags)
    > -{
    > - if (!transhuge_vma_enabled(vma, vm_flags))
    > - return false;
    > -
    > - if (vm_flags & VM_NO_KHUGEPAGED)
    > - return false;
    > -
    > - /* Don't run khugepaged against DAX vma */
    > - if (vma_is_dax(vma))
    > - return false;
    > -
    > - if (vma->vm_file && !IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) -
    > - vma->vm_pgoff, HPAGE_PMD_NR))
    > - return false;
    > -
    > - if (!transhuge_vma_size_ok(vma))
    > - return false;
    > -
    > - /* Enabled via shmem mount options or sysfs settings. */
    > - if (shmem_file(vma->vm_file))
    > - return shmem_huge_enabled(vma);
    > -
    > - if (!khugepaged_enabled())
    > - return false;
    > -
    > - /* THP settings require madvise. */
    > - if (!(vm_flags & VM_HUGEPAGE) && !khugepaged_always())
    > - return false;
    > -
    > - /* Only regular file is valid */
    > - if (file_thp_enabled(vma))
    > - return true;
    > -
    > - if (!vma->anon_vma || !vma_is_anonymous(vma))
    > - return false;
    > - if (vma_is_temporary_stack(vma))
    > - return false;
    > -
    > - return true;
    > -}
    > -
    > void __khugepaged_enter(struct mm_struct *mm)
    > {
    > struct mm_slot *mm_slot;
    > @@ -516,7 +473,7 @@ void khugepaged_enter_vma(struct vm_area_struct *vma,
    > {
    > if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags) &&
    > khugepaged_enabled()) {
    > - if (hugepage_vma_check(vma, vm_flags))
    > + if (hugepage_vma_check(vma, vm_flags, false))
    > __khugepaged_enter(vma->vm_mm);
    > }
    > }
    > @@ -961,7 +918,7 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
    >
    > if (!transhuge_vma_suitable(vma, address))
    > return SCAN_ADDRESS_RANGE;
    > - if (!hugepage_vma_check(vma, vma->vm_flags))
    > + if (!hugepage_vma_check(vma, vma->vm_flags, false))
    > return SCAN_VMA_CHECK;
    > return 0;
    > }
    > @@ -1442,7 +1399,7 @@ void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr)
    > * the valid THP. Add extra VM_HUGEPAGE so hugepage_vma_check()
    > * will not fail the vma for missing VM_HUGEPAGE
    > */
    > - if (!hugepage_vma_check(vma, vma->vm_flags | VM_HUGEPAGE))
    > + if (!hugepage_vma_check(vma, vma->vm_flags | VM_HUGEPAGE, false))
    > return;
    >
    > /* Keep pmd pgtable for uffd-wp; see comment in retract_page_tables() */
    > @@ -2132,7 +2089,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
    > progress++;
    > break;
    > }
    > - if (!hugepage_vma_check(vma, vma->vm_flags)) {
    > + if (!hugepage_vma_check(vma, vma->vm_flags, false)) {
    > skip:
    > progress++;
    > continue;
    > --
    > 2.26.3
    >
    >

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