Re: [PATCH v2 2/3] mm/damon/paddr: minor refactor of damon_pa_young()

[Kefeng Wang]

On 2023/3/8 2:00, SeongJae Park wrote:
> On Tue, 7 Mar 2023 09:22:33 +0800 Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> wrote:
>
> > On 2023/3/7 5:27, SeongJae Park wrote:
> > > Hi Kefeng,
> > >
> > > On Mon, 6 Mar 2023 09:56:49 +0800 Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> wrote:
> > >
> > > > On 2023/3/6 9:10, Kefeng Wang wrote:
> > > > > On 2023/3/4 2:39, SeongJae Park wrote:
> > > > > > Hi Kefeng,
> > > > > >
> > > > > > On Fri, 3 Mar 2023 16:43:42 +0800 Kefeng Wang
> > > > > > <wangkefeng.wang@xxxxxxxxxx> wrote:
> > > > > >
> > > > > > > Omit three lines by unified folio_put(), and make code more clear.
> > > > > > >
> > > > > > > Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
> > > > > > > ---
> > > > > > >     mm/damon/paddr.c | 11 ++++-------
> > > > > > >     1 file changed, 4 insertions(+), 7 deletions(-)
> > > > > > >
> > > > > > > diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
> > > > > > > index 3fda00a0f786..2ef9db0189ca 100644
> > > > > > > --- a/mm/damon/paddr.c
> > > > > > > +++ b/mm/damon/paddr.c
> > > > > > > @@ -130,24 +130,21 @@ static bool damon_pa_young(unsigned long paddr,
> > > > > > > unsigned long *folio_sz)
> > > > > > >                 accessed = false;
> > > > > > >             else
> > > > > > >                 accessed = true;
> > > > > > > -        folio_put(folio);
> > > > > > >             goto out;
> > > > > >
> > > > > > Because you moved 'out' label to not include *folio_sz setting,
> > > > > > folio_sz will
> > > > > > not set in this case.  It should be set.
> > > > > oh, it should be fixed.
> > > > > > >         }
> > > > > > >         need_lock = !folio_test_anon(folio) || folio_test_ksm(folio);
> > > > > > > -    if (need_lock && !folio_trylock(folio)) {
> > > > > > > -        folio_put(folio);
> > > > > > > -        return false;
> > > > > > > -    }
> > > >
> > > > Hi SJ,  apart from above issue, it looks that this branch need the
> > > > folio_size() setting, right?
> > >
> > > folio_sz is effectively used by caller of damon_pa_young() only if this
> > > function returns true, so this branch doesn't need to set folio_sz.
> >
> > __damon_pa_check_access() store last_addr, last_accessed and
> > last_folio_sz, even damon_pa_young() return false, the following check
> > still use last_folio_sz,
> >
> >     ALIGN_DOWN(last_addr, last_folio_sz) == ALIGN_DOWN(r->sampling_addr,
> > last_folio_sz)
> >
> > but last_folio_sz is not up to date, so I think it need to update, and
> > update last_folio_sz is harmless, which could let's unify the return
> > path, correct me if I am wrong.
>
> Ah, you're right.  Thank you for kind explanation.  I was out of my mind for
> some reason.  Maybe we could just do 'goto out' in the branch.

Yes, will update this patchset with this change.
> Thanks,
> SJ