From: Johannes Weiner Date: Wed, 20 Mar 2024 18:02:08 +0000 (-0400) Subject: mm: page_alloc: fix up block types when merging compatible blocks X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=e6cf9e1c4cde8a53385423ecb8ca581097f42e02;p=linux.git mm: page_alloc: fix up block types when merging compatible blocks The buddy allocator coalesces compatible blocks during freeing, but it doesn't update the types of the subblocks to match. When an allocation later breaks the chunk down again, its pieces will be put on freelists of the wrong type. This encourages incompatible page mixing (ask for one type, get another), and thus long-term fragmentation. Update the subblocks when merging a larger chunk, such that a later expand() will maintain freelist type hygiene. Link: https://lkml.kernel.org/r/20240320180429.678181-4-hannes@cmpxchg.org Signed-off-by: Johannes Weiner Reviewed-by: Zi Yan Reviewed-by: Vlastimil Babka Acked-by: Mel Gorman Tested-by: "Huang, Ying" Tested-by: Baolin Wang Cc: David Hildenbrand Signed-off-by: Andrew Morton --- diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 5fa3d534df2f9..2c03336def76f 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -786,10 +786,17 @@ static inline void __free_one_page(struct page *page, */ int buddy_mt = get_pfnblock_migratetype(buddy, buddy_pfn); - if (migratetype != buddy_mt - && (!migratetype_is_mergeable(migratetype) || - !migratetype_is_mergeable(buddy_mt))) - goto done_merging; + if (migratetype != buddy_mt) { + if (!migratetype_is_mergeable(migratetype) || + !migratetype_is_mergeable(buddy_mt)) + goto done_merging; + /* + * Match buddy type. This ensures that + * an expand() down the line puts the + * sub-blocks on the right freelists. + */ + set_pageblock_migratetype(buddy, migratetype); + } } /*