On 01/23/2017 04:39 PM, Mel Gorman wrote:
> buffered_rmqueue removes a page from a given zone and uses the per-cpu
> list for order-0. This is fine but a hypothetical caller that wanted
> multiple order-0 pages has to disable/reenable interrupts multiple
> times. This patch structures buffere_rmqueue such that it's relatively
> easy to build a bulk order-0 page allocator. There is no functional
> change.
>
> Signed-off-by: Mel Gorman <mgor...@techsingularity.net>
> Acked-by: Hillf Danton <hillf...@alibaba-inc.com>
Acked-by: Vlastimil Babka <vba...@suse.cz>
But I think you need a fix on top
[...]
> -struct page *buffered_rmqueue(struct zone *preferred_zone,
> +struct page *rmqueue(struct zone *preferred_zone,
> struct zone *zone, unsigned int order,
> gfp_t gfp_flags, unsigned int alloc_flags,
> int migratetype)
> {
> unsigned long flags;
> struct page *page;
> - bool cold = ((gfp_flags & __GFP_COLD) != 0);
>
> if (likely(order == 0)) {
> - struct per_cpu_pages *pcp;
> - struct list_head *list;
> -
> - local_irq_save(flags);
> - do {
> - pcp = &this_cpu_ptr(zone->pageset)->pcp;
> - list = &pcp->lists[migratetype];
> - if (list_empty(list)) {
> - pcp->count += rmqueue_bulk(zone, 0,
> - pcp->batch, list,
> - migratetype, cold);
> - if (unlikely(list_empty(list)))
> - goto failed;
> - }
> -
> - if (cold)
> - page = list_last_entry(list, struct page, lru);
> - else
> - page = list_first_entry(list, struct page, lru);
> -
> - list_del(&page->lru);
> - pcp->count--;
> + page = rmqueue_pcplist(preferred_zone, zone, order,
> + gfp_flags, migratetype);
> + goto out;
page might be NULL here...
> + }
>
> - } while (check_new_pcp(page));
> - } else {
> - /*
> - * We most definitely don't want callers attempting to
> - * allocate greater than order-1 page units with __GFP_NOFAIL.
> - */
> - WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
> - spin_lock_irqsave(&zone->lock, flags);
> + /*
> + * We most definitely don't want callers attempting to
> + * allocate greater than order-1 page units with __GFP_NOFAIL.
> + */
> + WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
> + spin_lock_irqsave(&zone->lock, flags);
>
> - do {
> - page = NULL;
> - if (alloc_flags & ALLOC_HARDER) {
> - page = __rmqueue_smallest(zone, order,
> MIGRATE_HIGHATOMIC);
> - if (page)
> - trace_mm_page_alloc_zone_locked(page,
> order, migratetype);
> - }
> - if (!page)
> - page = __rmqueue(zone, order, migratetype);
> - } while (page && check_new_pages(page, order));
> - spin_unlock(&zone->lock);
> + do {
> + page = NULL;
> + if (alloc_flags & ALLOC_HARDER) {
> + page = __rmqueue_smallest(zone, order,
> MIGRATE_HIGHATOMIC);
> + if (page)
> + trace_mm_page_alloc_zone_locked(page, order,
> migratetype);
> + }
> if (!page)
> - goto failed;
> - __mod_zone_freepage_state(zone, -(1 << order),
> - get_pcppage_migratetype(page));
> - }
> + page = __rmqueue(zone, order, migratetype);
> + } while (page && check_new_pages(page, order));
> + spin_unlock(&zone->lock);
> + if (!page)
> + goto failed;
> + __mod_zone_freepage_state(zone, -(1 << order),
> + get_pcppage_migratetype(page));
>
> __count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
> zone_statistics(preferred_zone, zone);
> local_irq_restore(flags);
>
> +out:
> VM_BUG_ON_PAGE(bad_range(zone, page), page);
... and then this explodes?
I guess the easiest fix is change the condition to
"page && bad_range(...)"
