On 30.06.25 18:01, Lorenzo Stoakes wrote:
On Mon, Jun 30, 2025 at 02:59:46PM +0200, David Hildenbrand wrote:
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.



Acked-by: Zi Yan <z...@nvidia.com>
Acked-by: Harry Yoo <harry....@oracle.com>
Signed-off-by: David Hildenbrand <da...@redhat.com>

On assumption this UINT_MAX stuff is sane :)) I mean this is straightforward I
guess:
> > Reviewed-by: Lorenzo Stoakes <lorenzo.stoa...@oracle.com>

---
  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


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