Re: [v4 PATCH 2/7] mm: thp: consolidate vma size check to transhuge_vma_suitable

Zach O'Keefe
2022-06-15T23:55:10Z

On 15 Jun 10:29, Yang Shi wrote:
> There are couple of places that check whether the vma size is ok for
> THP or whether address fits, they are open coded and duplicate, use
> transhuge_vma_suitable() to do the job by passing in (vma->end -
> HPAGE_PMD_SIZE).
>
> Move vma size check into hugepage_vma_check(). This will make
> khugepaged_enter() is as same as khugepaged_enter_vma(). There is just
> one caller for khugepaged_enter(), replace it to khugepaged_enter_vma()
> and remove khugepaged_enter().
>
> Signed-off-by: Yang Shi <shy828301@gmail.com>
> ---
> include/linux/huge_mm.h | 11 +++++++++++
> include/linux/khugepaged.h | 14 --------------
> mm/huge_memory.c | 2 +-
> mm/khugepaged.c | 19 ++++++-------------
> 4 files changed, 18 insertions(+), 28 deletions(-)
>
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index 648cb3ce7099..8a5a8bfce0f5 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -116,6 +116,17 @@ extern struct kobj_attribute shmem_enabled_attr;
>
> extern unsigned long transparent_hugepage_flags;
>
> +/*
> + * Do the below checks:
> + * - For file vma, check if the linear page offset of vma is
> + * HPAGE_PMD_NR aligned within the file. The hugepage is
> + * guaranteed to be hugepage-aligned within the file, but we must
> + * check that the PMD-aligned addresses in the VMA map to
> + * PMD-aligned offsets within the file, else the hugepage will
> + * not be PMD-mappable.
> + * - For all vmas, check if the haddr is in an aligned HPAGE_PMD_SIZE
> + * area.
> + */
> static inline bool transhuge_vma_suitable(struct vm_area_struct *vma,
> unsigned long addr)
> {
> diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h
> index 392d34c3c59a..31ca8a7f78f4 100644
> --- a/include/linux/khugepaged.h
> +++ b/include/linux/khugepaged.h
> @@ -51,16 +51,6 @@ static inline void khugepaged_exit(struct mm_struct *mm)
> if (test_bit(MMF_VM_HUGEPAGE, &mm->flags))
> __khugepaged_exit(mm);
> }
> -
> -static inline void khugepaged_enter(struct vm_area_struct *vma,
> - unsigned long vm_flags)
> -{
> - if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags) &&
> - khugepaged_enabled()) {
> - if (hugepage_vma_check(vma, vm_flags))
> - __khugepaged_enter(vma->vm_mm);
> - }
> -}
> #else /* CONFIG_TRANSPARENT_HUGEPAGE */
> static inline void khugepaged_fork(struct mm_struct *mm, struct mm_struct *oldmm)
> {
> @@ -68,10 +58,6 @@ static inline void khugepaged_fork(struct mm_struct *mm, struct mm_struct *oldmm
> static inline void khugepaged_exit(struct mm_struct *mm)
> {
> }
> -static inline void khugepaged_enter(struct vm_area_struct *vma,
> - unsigned long vm_flags)
> -{
> -}
> static inline void khugepaged_enter_vma(struct vm_area_struct *vma,
> unsigned long vm_flags)
> {
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 4f9bbb4eab23..b530462c4493 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -726,7 +726,7 @@ vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
> return VM_FAULT_FALLBACK;
> if (unlikely(anon_vma_prepare(vma)))
> return VM_FAULT_OOM;
> - khugepaged_enter(vma, vma->vm_flags);
> + khugepaged_enter_vma(vma, vma->vm_flags);
>
> if (!(vmf->flags & FAULT_FLAG_WRITE) &&
> !mm_forbids_zeropage(vma->vm_mm) &&
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index b1dab94c0f1e..db0b334a7d1f 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -450,8 +450,8 @@ bool hugepage_vma_check(struct vm_area_struct *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))
> + /* Check alignment for file vma and size for both file and anon vma */
> + if (!transhuge_vma_suitable(vma, (vma->vm_end - HPAGE_PMD_SIZE)))
> return false;
>
> /* Enabled via shmem mount options or sysfs settings. */
> @@ -512,9 +512,7 @@ void khugepaged_enter_vma(struct vm_area_struct *vma,
> unsigned long vm_flags)
> {
> if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags) &&
> - khugepaged_enabled() &&
> - (((vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK) <
> - (vma->vm_end & HPAGE_PMD_MASK))) {
> + khugepaged_enabled()) {
> if (hugepage_vma_check(vma, vm_flags))
> __khugepaged_enter(vma->vm_mm);
> }
> @@ -950,7 +948,6 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
> struct vm_area_struct **vmap)
> {
> struct vm_area_struct *vma;
> - unsigned long hstart, hend;
>
> if (unlikely(khugepaged_test_exit(mm)))
> return SCAN_ANY_PROCESS;
> @@ -959,9 +956,7 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
> if (!vma)
> return SCAN_VMA_NULL;
>
> - hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
> - hend = vma->vm_end & HPAGE_PMD_MASK;
> - if (address < hstart || address + HPAGE_PMD_SIZE > hend)
> + if (!transhuge_vma_suitable(vma, address))
> return SCAN_ADDRESS_RANGE;
> if (!hugepage_vma_check(vma, vma->vm_flags))
> return SCAN_VMA_CHECK;
> @@ -2147,10 +2142,8 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
> progress++;
> continue;
> }
> - hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
> - hend = vma->vm_end & HPAGE_PMD_MASK;
> - if (hstart >= hend)
> - goto skip;
> + hstart = round_up(vma->vm_start, HPAGE_PMD_SIZE);
> + hend = round_down(vma->vm_end, HPAGE_PMD_SIZE);
> if (khugepaged_scan.address > hend)
> goto skip;
> if (khugepaged_scan.address < hstart)
> --
> 2.26.3
>

Thanks for the patches, Yang.

Reviewed-by: Zach O'Keefe <zokeefe@google.com>