Re: [v3 PATCH 6/8] mm: khugepaged: move some khugepaged_* functions to khugepaged.c

[Yang Shi <shy828301@gmail.com>]

On Mon, May 9, 2022 at 8:31 AM Vlastimil Babka <vbabka@suse.cz> wrote:
>
> On 4/4/22 22:02, Yang Shi wrote:
> > To reuse hugepage_vma_check() for khugepaged_enter() so that we could
> > remove some duplicate code.  But moving hugepage_vma_check() to
> > khugepaged.h needs to include huge_mm.h in it, it seems not optimal to
> > bloat khugepaged.h.
> >
> > And the khugepaged_* functions actually are wrappers for some non-inline
> > functions, so it seems the benefits are not too much to keep them inline.
> >
> > So move the khugepaged_* functions to khugepaged.c, any callers just
> > need to include khugepaged.h which is quite small.  For example, the
> > following patches will call khugepaged_enter() in filemap page fault path
> > for regular filesystems to make readonly FS THP collapse more consistent.
> > The  filemap.c just needs to include khugepaged.h.
>
> This last part is inaccurate in v3?

Yeah, thanks for catching this. Since the patch will be reworked, so
the commit log will be reworked as well.

>
> > Acked-by: Song Liu <song@kernel.org>
> > Signed-off-by: Yang Shi <shy828301@gmail.com>
>
> I think moving the tiny wrappers is unnecessary.
>
> How about just making hugepage_vma_check() not static and declare it in
> khugepaged.h, then it can be used from khugepaged_enter() in the same file
> and AFAICS no need to include huge_mm.h there?

Sounds good to me, will fix it in v4. Thanks for reviewing and acking
the series.

>
> > ---
> >  include/linux/khugepaged.h | 37 ++++++-------------------------------
> >  mm/khugepaged.c            | 20 ++++++++++++++++++++
> >  2 files changed, 26 insertions(+), 31 deletions(-)
> >
> > diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h
> > index 0423d3619f26..6acf9701151e 100644
> > --- a/include/linux/khugepaged.h
> > +++ b/include/linux/khugepaged.h
> > @@ -2,10 +2,6 @@
> >  #ifndef _LINUX_KHUGEPAGED_H
> >  #define _LINUX_KHUGEPAGED_H
> >
> > -#include <linux/sched/coredump.h> /* MMF_VM_HUGEPAGE */
> > -#include <linux/shmem_fs.h>
> > -
> > -
> >  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> >  extern struct attribute_group khugepaged_attr_group;
> >
> > @@ -16,6 +12,12 @@ extern void __khugepaged_enter(struct mm_struct *mm);
> >  extern void __khugepaged_exit(struct mm_struct *mm);
> >  extern void khugepaged_enter_vma_merge(struct vm_area_struct *vma,
> >                                      unsigned long vm_flags);
> > +extern void khugepaged_fork(struct mm_struct *mm,
> > +                         struct mm_struct *oldmm);
> > +extern void khugepaged_exit(struct mm_struct *mm);
> > +extern void khugepaged_enter(struct vm_area_struct *vma,
> > +                          unsigned long vm_flags);
> > +
> >  extern void khugepaged_min_free_kbytes_update(void);
> >  #ifdef CONFIG_SHMEM
> >  extern void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr);
> > @@ -33,36 +35,9 @@ static inline void collapse_pte_mapped_thp(struct mm_struct *mm,
> >  #define khugepaged_always()                          \
> >       (transparent_hugepage_flags &                   \
> >        (1<<TRANSPARENT_HUGEPAGE_FLAG))
> > -#define khugepaged_req_madv()                                        \
> > -     (transparent_hugepage_flags &                           \
> > -      (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG))
> >  #define khugepaged_defrag()                                  \
> >       (transparent_hugepage_flags &                           \
> >        (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG))
> > -
> > -static inline void khugepaged_fork(struct mm_struct *mm, struct mm_struct *oldmm)
> > -{
> > -     if (test_bit(MMF_VM_HUGEPAGE, &oldmm->flags))
> > -             __khugepaged_enter(mm);
> > -}
> > -
> > -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))
> > -             if ((khugepaged_always() ||
> > -                  (shmem_file(vma->vm_file) && shmem_huge_enabled(vma)) ||
> > -                  (khugepaged_req_madv() && (vm_flags & VM_HUGEPAGE))) &&
> > -                 !(vm_flags & VM_NOHUGEPAGE) &&
> > -                 !test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
> > -                     __khugepaged_enter(vma->vm_mm);
> > -}
> >  #else /* CONFIG_TRANSPARENT_HUGEPAGE */
> >  static inline void khugepaged_fork(struct mm_struct *mm, struct mm_struct *oldmm)
> >  {
> > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > index b69eda934d70..ec5b0a691d87 100644
> > --- a/mm/khugepaged.c
> > +++ b/mm/khugepaged.c
> > @@ -556,6 +556,26 @@ void __khugepaged_exit(struct mm_struct *mm)
> >       }
> >  }
> >
> > +void khugepaged_fork(struct mm_struct *mm, struct mm_struct *oldmm)
> > +{
> > +     if (test_bit(MMF_VM_HUGEPAGE, &oldmm->flags))
> > +             __khugepaged_enter(mm);
> > +}
> > +
> > +void khugepaged_exit(struct mm_struct *mm)
> > +{
> > +     if (test_bit(MMF_VM_HUGEPAGE, &mm->flags))
> > +             __khugepaged_exit(mm);
> > +}
> > +
> > +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);
> > +}
> > +
> >  static void release_pte_page(struct page *page)
> >  {
> >       mod_node_page_state(page_pgdat(page),
>