On 28.08.25 17:00, Lorenzo Stoakes wrote:
On Thu, Aug 28, 2025 at 12:01:14AM +0200, David Hildenbrand wrote:
Let's sanity-check in folio_set_order() whether we would be trying to
create a folio with an order that would make it exceed MAX_FOLIO_ORDER.
This will enable the check whenever a folio/compound page is initialized
through prepare_compound_head() / prepare_compound_page().
NIT: with CONFIG_DEBUG_VM set :)
Yes, will add that.
Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
LGTM (apart from nit below), so:
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
---
mm/internal.h | 1 +
1 file changed, 1 insertion(+)
diff --git a/mm/internal.h b/mm/internal.h
index 45da9ff5694f6..9b0129531d004 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -755,6 +755,7 @@ static inline void folio_set_order(struct folio *folio, unsigned int order)
{
if (WARN_ON_ONCE(!order || !folio_test_large(folio)))
return;
+ VM_WARN_ON_ONCE(order > MAX_FOLIO_ORDER);
Given we have 'full-fat' WARN_ON*()'s above, maybe worth making this one too?
The idea is that if you reach this point here, previous such checks I
added failed. So this is the safety net, and for that VM_WARN_ON_ONCE()
is sufficient.
I think we should rather convert the WARN_ON_ONCE to VM_WARN_ON_ONCE()
at some point, because no sane code should ever trigger that.
--
Cheers
David / dhildenb