On Mon 05-11-18 10:14:07, Michal Hocko wrote:
Maybe we can add a retry for movable zone pages.
Or something like this. Ugly as hell, no question about that. I also have to think about this some more to convince myself this will not result in an endless loop under some situations.
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 48ceda313332..342d66eca0f3 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7779,12 +7779,16 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, pfn = page_to_pfn(page); for (found = 0, iter = 0; iter < pageblock_nr_pages; iter++) { unsigned long check = pfn + iter; + unsigned long saved_flags;
if (!pfn_valid_within(check)) continue;
page = pfn_to_page(check);
+retry: + saved_flags = READ_ONCE(page->flags); + if (PageReserved(page)) goto unmovable;
@@ -7840,6 +7844,13 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, page->mapping->a_ops->migratepage) continue;
+ /* + * We might race with the allocation of the page so retry + * if flags have changed. + */ + if (saved_flags != READ_ONCE(page->flags)) + goto retry; + /* * If there are RECLAIMABLE pages, we need to check * it. But now, memory offline itself doesn't call