On Tue, Sep 8, 2020 at 6:01 PM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
>
> On Mon, Aug 24, 2020 at 08:55:04PM +0800, Alex Shi wrote:
> > +++ b/mm/vmscan.c
> > @@ -1688,10 +1688,13 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
> >
> > if (!TestClearPageLRU(page)) {
> > /*
> > - * This page may in other isolation path,
> > - * but we still hold lru_lock.
> > + * This page is being isolated in another
> > + * thread, but we still hold lru_lock. The
> > + * other thread must be holding a reference
> > + * to the page so this should never hit a
> > + * reference count of 0.
> > */
> > - put_page(page);
> > + WARN_ON(put_page_testzero(page));
> > goto busy;
>
> I read Hugh's review and that led me to take a look at this. We don't
> do it like this. Use the same pattern as elsewhere in mm:
>
> page_ref_sub(page, nr);
> VM_BUG_ON_PAGE(page_count(page) <= 0, page);
>
>
Actually for this case page_ref_dec(page) would make more sense
wouldn't it? Otherwise I agree that would be a better change if that
is the way it has been handled before. I just wasn't familiar with
those other spots.
Thanks.
- Alex
