On Fri, Dec 02, 2016 at 11:04:11AM +0100, Michal Hocko wrote: > On Fri 02-12-16 17:30:07, Hillf Danton wrote: > [...] > > > >> @@ -2217,13 +2217,14 @@ static int rmqueue_bulk(struct zone *zone, > > > >> unsigned int order, > > > >> else > > > >> list_add_tail(&page->lru, list); > > > >> list = &page->lru; > > > >> + alloced++; > > > >> if (is_migrate_cma(get_pcppage_migratetype(page))) > > > >> __mod_zone_page_state(zone, NR_FREE_CMA_PAGES, > > > >> -(1 << order)); > > > >> } > > > >> __mod_zone_page_state(zone, NR_FREE_PAGES, -(i << order)); > > > > > > > > Now i is a pure index, yes? > > > > > > No, even if a page fails the check_pcp_refill() check and is not > > > "allocated", it is also no longer a free page, so it's correct to > > > subtract it from NR_FREE_PAGES. > > > > > Yes, we can allocate free page next time. > > No we cannot. The page is gone from the free list. We have effectively > leaked it.
And deliberately so. It's in an unknown state, possibly due to memory corruption or a use-after free bug. The machine can continue limping on with warnings in the kernel log but the VM stops going near the page itself as much as possible. -- Mel Gorman SUSE Labs
