[PATCH v7 31/31] mm: balloon: use put_page_zeroed for zeroed balloon pages

["Michael S. Tsirkin" <mst@redhat.com>]

When a balloon page marked PageZeroed is freed during migration,
use put_page_zeroed() to propagate the zeroed hint to the buddy
allocator. Previously the hint was silently lost via plain put_page().

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Assisted-by: Claude:claude-opus-4-6
---
 mm/balloon.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/mm/balloon.c b/mm/balloon.c
index 96a8f1e20bc6..1bf7eb2642a9 100644
--- a/mm/balloon.c
+++ b/mm/balloon.c
@@ -324,7 +324,12 @@ static int balloon_page_migrate(struct page *newpage, struct page *page,
 	balloon_page_finalize(page);
 	spin_unlock_irqrestore(&balloon_pages_lock, flags);
 
-	put_page(page);
+	if (PageZeroed(page)) {
+		__ClearPageZeroed(page);
+		put_page_zeroed(page);
+	} else {
+		put_page(page);
+	}
 
 	return 0;
 }
-- 
MST