From: Muchun Song <songmuchun@xxxxxxxxxxxxx> Subject: mm/page_isolation: do not isolate the max order page A max order page has no buddy page and never merges to another order. So isolating and then freeing it is pointless. Link: https://lkml.kernel.org/r/20201202122114.75316-1-songmuchun@xxxxxxxxxxxxx Fixes: 3c605096d315 ("mm/page_alloc: restrict max order of merging on isolated pageblock") Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx> Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx> Reviewed-by: Oscar Salvador <osalvador@xxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/page_isolation.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/page_isolation.c~mm-page_isolation-do-not-isolate-the-max-order-page +++ a/mm/page_isolation.c @@ -88,7 +88,7 @@ static void unset_migratetype_isolate(st */ if (PageBuddy(page)) { order = buddy_order(page); - if (order >= pageblock_order) { + if (order >= pageblock_order && order < MAX_ORDER - 1) { pfn = page_to_pfn(page); buddy_pfn = __find_buddy_pfn(pfn, order); buddy = page + (buddy_pfn - pfn); _
