* Hillf Danton <hdanton@xxxxxxxx> [210504 00:29]:
> On Wed, 28 Apr 2021 15:36:24 Liam R. Howlett wrote:
> > ---
> > mm/khugepaged.c | 11 +++++++++--
> > 1 file changed, 9 insertions(+), 2 deletions(-)
>
> Good work. And a nit below.
> >
> > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > index 33cf91529f0b..4983a25c5a90 100644
> > --- a/mm/khugepaged.c
> > +++ b/mm/khugepaged.c
> > @@ -2063,6 +2063,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned =
> > int pages,
> > struct mm_struct *mm;
> > struct vm_area_struct *vma;
> > int progress = 0;
> > + MA_STATE(mas, NULL, 0, 0);
> >
> > VM_BUG_ON(!pages);
> > lockdep_assert_held(&khugepaged_mm_lock);
> > @@ -2079,18 +2080,22 @@ static unsigned int khugepaged_scan_mm_slot(unsigne=
> > d int pages,
> > khugepaged_collapse_pte_mapped_thps(mm_slot);
> >
> > mm = mm_slot->mm;
> > + mas.tree = &mm->mm_mt;
> > /*
> > * Don't wait for semaphore (to avoid long wait times). Just move to
> > * the next mm on the list.
> > */
> > vma = NULL;
> > + mas_set(&mas, khugepaged_scan.address);
> > if (unlikely(!mmap_read_trylock(mm)))
> > goto breakouterloop_mmap_lock;
> > +
> > + rcu_read_lock();
> > if (likely(!khugepaged_test_exit(mm)))
> > - vma = find_vma(mm, khugepaged_scan.address);
> > + vma = mas_find(&mas, ULONG_MAX);
> >
> > progress++;
> > - for (; vma; vma = vma->vm_next) {
> > + mas_for_each(&mas, vma, ULONG_MAX) {
> > unsigned long hstart, hend;
> >
> > cond_resched();
>
> Given the added rcu_read_lock(), take another look at this scheduling
> entry?
>
Yes, thank you for pointing this out. It is certainly an issue.
> > @@ -2129,6 +2134,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned =
> > int pages,
> > pgoff_t pgoff = linear_page_index(vma,
> > khugepaged_scan.address);
> >
> > + rcu_read_unlock();
> > mmap_read_unlock(mm);
> > ret = 1;
> > khugepaged_scan_file(mm, file, pgoff, hpage);
> > @@ -2149,6 +2155,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned =
> > int pages,
> > }
> > }
> > breakouterloop:
> > + rcu_read_unlock();
> > mmap_read_unlock(mm); /* exit_mmap will destroy ptes after this */
> > breakouterloop_mmap_lock:
> >
> > --
> > 2.30.2
