lkml.org 
[lkml]   [2022]   [Mar]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH] mm: thp: don't have to lock page anymore when splitting PMD
On Mon, Mar 7, 2022 at 4:50 PM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Mon, 7 Mar 2022 16:03:12 -0800 Yang Shi <shy828301@gmail.com> wrote:
>
> > On Mon, Mar 7, 2022 at 3:43 PM Andrew Morton <akpm@linux-foundation.org> wrote:
> > > @@ -2133,8 +2133,6 @@ void __split_huge_pmd(struct vm_area_str
> > > {
> > > spinlock_t *ptl;
> > > struct mmu_notifier_range range;
> > > - bool do_unlock_folio = false;
> > > - pmd_t _pmd;
> > >
> > > mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
> > > address & HPAGE_PMD_MASK,
> > > @@ -2153,42 +2151,14 @@ void __split_huge_pmd(struct vm_area_str
> > > goto out;
> > > }
> > >
> > > -repeat:
> > > if (pmd_trans_huge(*pmd)) {
> > > - if (!folio) {
> > > + if (!folio)
> > > folio = page_folio(pmd_page(*pmd));
> >
> > We could remove the "if (pmd_trans_huge(*pmd))" section since folio is
> > actually not used afterward at all.
>
> >
> > ...
> >
> >
> > With the above if removed, this could be changed to:
> >
> > if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) ||
> > is_pmd_migration_entry(*pmd))
> > __split_huge_pmd_locked(vma, pmd, range.start, freeze);
> >
>
> OK, looks sane. Can someone please test all this?

Build test? I had the exact same change in my tree, it worked for me.


>
> --- a/mm/huge_memory.c~mm-huge_memory-remove-stale-locking-logic-from-__split_huge_pmd-fix
> +++ a/mm/huge_memory.c
> @@ -2151,12 +2151,10 @@ void __split_huge_pmd(struct vm_area_str
> goto out;
> }
>
> - if (pmd_trans_huge(*pmd)) {
> - if (!folio)
> - folio = page_folio(pmd_page(*pmd));
> - } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd)))
> - goto out;
> - __split_huge_pmd_locked(vma, pmd, range.start, freeze);
> + if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) ||
> + is_pmd_migration_entry(*pmd)))
> + __split_huge_pmd_locked(vma, pmd, range.start, freeze);
> +
> out:
> spin_unlock(ptl);
> /*
> _
>

\
 
 \ /
  Last update: 2022-03-08 02:00    [W:0.043 / U:0.400 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site