On 4/6/19 7:59 AM, Pankaj Suryawanshi wrote: > Hello , > > shrink_page_list() returns , number of pages reclaimed, when pages is > unevictable it returns VM_BUG_ON_PAGE(PageLRU(page) || > PageUnevicatble(page),page); > > We can add the unevictable pages in reclaim list in > shrink_page_list(), return total number of reclaim pages including > unevictable pages, let the caller handle unevictable pages. > > I think the problem is shrink_page_list is awkard. If page is > unevictable it goto activate_locked->keep_locked->keep lables, keep > lable list_add the unevictable pages and throw the VM_BUG instead of > passing it to caller while it relies on caller for > non-reclaimed-non-unevictable page's putback. > I think we can make it consistent so that shrink_page_list could > return non-reclaimed pages via page_list and caller can handle it. As > an advance, it could try to migrate mlocked pages without retrial. > > > Below is the issue i observed of CMA_ALLOC of large size buffer : > (Kernel version - 4.14.65 With Android Pie. > > [ 24.718792] page dumped because: VM_BUG_ON_PAGE(PageLRU(page) || > PageUnevictable(page)) > [ 24.726949] page->mem_cgroup:bd008c00 > [ 24.730693] ------------[ cut here ]------------ > [ 24.735304] kernel BUG at mm/vmscan.c:1350! > [ 24.739478] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM Please include full report including the full stacktrace, kernel version etc etc. > > > Below is the patch which solved this issue : > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index be56e2e..12ac353 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -998,7 +998,7 @@ static unsigned long shrink_page_list(struct > list_head *page_list, > sc->nr_scanned++; > > if (unlikely(!page_evictable(page))) > - goto activate_locked; > + goto cull_mlocked; > > if (!sc->may_unmap && page_mapped(page)) > goto keep_locked; > @@ -1331,7 +1331,12 @@ static unsigned long shrink_page_list(struct > list_head *page_list, > } else > list_add(&page->lru, &free_pages); > continue; > - > +cull_mlocked: > + if (PageSwapCache(page)) > + try_to_free_swap(page); > + unlock_page(page); > + list_add(&page->lru, &ret_pages); > + continue; > activate_locked: > /* Not a candidate for swapping, so reclaim swap space. */ > if (PageSwapCache(page) && (mem_cgroup_swap_full(page) || > > > > > It fixes the below issue. > > 1. Large size buffer allocation using cma_alloc successful with > unevictable pages. > > cma_alloc of current kernel will fail due to unevictable page > > Please let me know if anything i am missing. > > Regards, > Pankaj >
