From 3da0272a4c7d0d37b47b28e87014f421296fc2be Mon Sep 17 00:00:00 2001 From: Kemeng Shi Date: Fri, 1 Sep 2023 23:51:38 +0800 Subject: mm/compaction: correctly return failure with bogus compound_order in strict mode In strict mode, we should return 0 if there is any hole in pageblock. If we successfully isolated pages at beginning at pageblock and then have a bogus compound_order outside pageblock in next page. We will abort search loop with blockpfn > end_pfn. Although we will limit blockpfn to end_pfn, we will treat it as a successful isolation in strict mode as blockpfn is not < end_pfn and return partial isolated pages. Then isolate_freepages_range may success unexpectly with hole in isolated range. Link: https://lkml.kernel.org/r/20230901155141.249860-4-shikemeng@huaweicloud.com Fixes: 9fcd6d2e052e ("mm, compaction: skip compound pages by order in free scanner") Signed-off-by: Kemeng Shi Reviewed-by: Baolin Wang Acked-by: Mel Gorman Cc: David Hildenbrand Cc: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton --- mm/compaction.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/mm/compaction.c b/mm/compaction.c index a40550a33aee..9ecbfbc695e5 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -626,11 +626,12 @@ static unsigned long isolate_freepages_block(struct compact_control *cc, if (PageCompound(page)) { const unsigned int order = compound_order(page); - if (likely(order <= MAX_ORDER)) { + if (blockpfn + (1UL << order) <= end_pfn) { blockpfn += (1UL << order) - 1; page += (1UL << order) - 1; nr_scanned += (1UL << order) - 1; } + goto isolate_fail; } @@ -678,8 +679,7 @@ isolate_fail: spin_unlock_irqrestore(&cc->zone->lock, flags); /* - * There is a tiny chance that we have read bogus compound_order(), - * so be careful to not go outside of the pageblock. + * Be careful to not go outside of the pageblock. */ if (unlikely(blockpfn > end_pfn)) blockpfn = end_pfn; -- cgit v1.2.3