On 30.06.25 18:01, Lorenzo Stoakes wrote:

On Mon, Jun 30, 2025 at 02:59:46PM +0200, David Hildenbrand wrote:

quoted

Let the page freeing code handle clearing the page type.

Why is this advantageous? We want to keep the page marked offline for longer?

Less code? ;)

I will add:

"Being able to identify balloon pages until actually freed is a 
requirement for upcoming movable_ops migration changes."

Note that the documentation is extended in patch #27 to mention that.

quoted

Acked-by: Zi Yan <ziy@nvidia.com>
Acked-by: Harry Yoo <redacted>
Signed-off-by: David Hildenbrand <redacted>

On assumption this UINT_MAX stuff is sane :)) I mean this is straightforward I
guess:

 > > Reviewed-by: Lorenzo Stoakes [off-list ref]

quoted

---
  include/linux/balloon_compaction.h | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/balloon_compaction.h b/include/linux/balloon_compaction.h
index b9f19da37b089..bfc6e50bd004b 100644
--- a/include/linux/balloon_compaction.h
+++ b/include/linux/balloon_compaction.h

@@ -140,7 +140,7 @@ static inline void balloon_page_finalize(struct page *page)
  		__ClearPageMovable(page);
  		set_page_private(page, 0);
  	}
-	__ClearPageOffline(page);
+	/* PageOffline is sticky until the page is freed to the buddy. */

OK so we are relying on this UINT_MAX thing in free_pages_prepare() to handle this.

Yes. Resetting the page_type -> _mapcount to the initial value -1.

-- 
Cheers,

David / dhildenb