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

[Kefeng Wang]

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?

Thanks

> > > +    if (need_lock && !folio_trylock(folio))
> > > +        goto out;
> > >       rmap_walk(folio, &rwc);
> > >       if (need_lock)
> > >           folio_unlock(folio);
> > > -    folio_put(folio);
> > > -out:
> > >       *folio_sz = folio_size(folio);
> > > +out:
> > > +    folio_put(folio);
> >
> > Before this change, folio_size() is called after folio_put().  
> > Shouldn't it be
> > called before folio_put()?  If so, could we make a separate fix for 
> > that first,
> > and then make this change on top of it, so that it can be easily 
> > applied to
> > relevant stable kernels?
> Yes， I could separate it, after folio_put(), the folio could be 
> re-allocated and the folio_size calculation is not right.
> > Thanks,
> > SJ
> >
> > >       return accessed;
> > >   }
> > > --
> > > 2.35.3