From: Johannes Weiner Date: Wed, 20 Mar 2024 18:02:10 +0000 (-0400) Subject: mm: page_alloc: fix move_freepages_block() range error X-Git-Tag: v6.10-rc1~105^2~344 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=2dd482ba627d;p=thirdparty%2Flinux.git mm: page_alloc: fix move_freepages_block() range error When a block is partially outside the zone of the cursor page, the function cuts the range to the pivot page instead of the zone start. This can leave large parts of the block behind, which encourages incompatible page mixing down the line (ask for one type, get another), and thus long-term fragmentation. This triggers reliably on the first block in the DMA zone, whose start_pfn is 1. The block is stolen, but everything before the pivot page (which was often hundreds of pages) is left on the old list. Link: https://lkml.kernel.org/r/20240320180429.678181-6-hannes@cmpxchg.org Signed-off-by: Johannes Weiner Reviewed-by: Vlastimil Babka Tested-by: Baolin Wang Cc: David Hildenbrand Cc: "Huang, Ying" Cc: Mel Gorman Cc: Zi Yan Signed-off-by: Andrew Morton --- diff --git a/mm/page_alloc.c b/mm/page_alloc.c index dcacb86efd298..0e223d5b94fa5 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1650,9 +1650,15 @@ int move_freepages_block(struct zone *zone, struct page *page, start_pfn = pageblock_start_pfn(pfn); end_pfn = pageblock_end_pfn(pfn) - 1; - /* Do not cross zone boundaries */ + /* + * The caller only has the lock for @zone, don't touch ranges + * that straddle into other zones. While we could move part of + * the range that's inside the zone, this call is usually + * accompanied by other operations such as migratetype updates + * which also should be locked. + */ if (!zone_spans_pfn(zone, start_pfn)) - start_pfn = pfn; + return 0; if (!zone_spans_pfn(zone, end_pfn)) return 0;