On Sun, May 3, 2020 at 8:10 PM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > > On Wed, Apr 29, 2020 at 06:36:50AM -0700, Matthew Wilcox wrote: > > @@ -886,7 +906,7 @@ static int __add_to_page_cache_locked(struct page *page, > > /* Leave page->index set: truncation relies upon it */ > > if (!huge) > > mem_cgroup_cancel_charge(page, memcg, false); > > - put_page(page); > > + page_ref_sub(page, nr); > > return xas_error(&xas); > > } > > ALLOW_ERROR_INJECTION(__add_to_page_cache_locked, ERRNO); > > This is wrong. page_ref_sub() will not call __put_page() if the refcount > gets to zero. What do people prefer? > > - put_page(page); > > (a) > + put_thp(page); > > (b) > + put_page_nr(page, nr); > > (c) > + if (page_ref_sub_return(page, nr) == 0) > + __put_page(page); b or c IMHO. The shmem uses page_ref_add/page_ref_sub so we'd better follow it. If go with b, it sounds better to add get_page_nr() as well. >
