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Shutemov" , Rong Chen , Michal Hocko , Vladimir Davydov , shy828301@gmail.com, Alexander Duyck Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 1B403180F8B81 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Sep 8, 2020 at 6:01 PM Matthew Wilcox 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