mm, compaction: require only min watermarks for non-costly orders

[cascardo/linux.git] / mm / page_alloc.c

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index a2214c6..c988d32 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2489,9 +2489,14 @@ int __isolate_free_page(struct page *page, unsigned int order)
        mt = get_pageblock_migratetype(page);
 
        if (!is_migrate_isolate(mt)) {
-               /* Obey watermarks as if the page was being allocated */
-               watermark = low_wmark_pages(zone) + (1 << order);
-               if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
+               /*
+                * Obey watermarks as if the page was being allocated. We can
+                * emulate a high-order watermark check with a raised order-0
+                * watermark, because we already know our high-order page
+                * exists.
+                */
+               watermark = min_wmark_pages(zone) + (1UL << order);
+               if (!zone_watermark_ok(zone, 0, watermark, 0, ALLOC_CMA))
                        return 0;
 
                __mod_zone_freepage_state(zone, -(1UL << order), mt);