When splitting a large buddy page, propagate the PG_zeroed flag to each sub-page before freeing it. __free_pages_prepare clears all flags (including PG_zeroed), so the flag must be re-set on each fragment after the split. This ensures that the buddy merge logic can see PG_zeroed on pages that were part of a larger zeroed block.
Signed-off-by: Michael S. Tsirkin <[email protected]> Reviewed-by: Gregory Price <[email protected]> Assisted-by: Claude:claude-opus-4-6 Assisted-by: cursor-agent:GPT-5.4-xhigh --- mm/page_alloc.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 7a6dedd716e2..21f9e92922f1 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1520,6 +1520,7 @@ static void split_large_buddy(struct zone *zone, struct page *page, bool reported) { unsigned long end = pfn + (1 << order); + bool zeroed = PageZeroed(page); VM_WARN_ON_ONCE(!IS_ALIGNED(pfn, 1 << order)); /* Caller removed page from freelist, buddy info cleared! */ @@ -1531,6 +1532,8 @@ static void split_large_buddy(struct zone *zone, struct page *page, do { int mt = get_pfnblock_migratetype(page, pfn); + if (zeroed) + __SetPageZeroed(page); __free_one_page(page, pfn, zone, order, mt, fpi); if (reported && PageBuddy(page) && buddy_order(page) == order) __SetPageReported(page); -- MST
