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@nvidia.com Signed-off-by: David Hildenbrand david@redhat.com
LGTM (apart from nit below), so:
Reviewed-by: Lorenzo Stoakes lorenzo.stoakes@oracle.com
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.