On Mon, 10 Aug 2020, Charan Teja Reddy wrote:
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index e4896e6..25e7e12 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3106,6 +3106,7 @@ static void free_unref_page_commit(struct page *page,
> unsigned long pfn)
> struct zone *zone = page_zone(page);
> struct per_cpu_pages *pcp;
> int migratetype;
> + int high;
>
> migratetype = get_pcppage_migratetype(page);
> __count_vm_event(PGFREE);
> @@ -3128,8 +3129,19 @@ static void free_unref_page_commit(struct page *page,
> unsigned long pfn)
> pcp = &this_cpu_ptr(zone->pageset)->pcp;
> list_add(&page->lru, &pcp->lists[migratetype]);
> pcp->count++;
> - if (pcp->count >= pcp->high) {
> - unsigned long batch = READ_ONCE(pcp->batch);
> + high = READ_ONCE(pcp->high);
> + if (pcp->count >= high) {
> + int batch;
> +
> + batch = READ_ONCE(pcp->batch);
> + /*
> + * For non-default pcp struct values, high is always
> + * greater than the batch. If high < batch then pass
> + * proper count to free the pcp's list pages.
> + */
> + if (unlikely(high < batch))
> + batch = min(pcp->count, batch);
> +
> free_pcppages_bulk(zone, batch, pcp);
> }
> }
I'm wondering if a fix to free_pcppages_bulk() is more appropriate here
because the count passed into it seems otherwise fragile if this results
in a hung core?
