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[PATCH v1 10/36] mm: sanity-check maximum folio size in folio_set_order()

David Hildenbrand posted 36 patches 1 month ago
There is a newer version of this series
[PATCH v1 10/36] mm: sanity-check maximum folio size in folio_set_order()
Posted by David Hildenbrand 1 month ago 
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().

Reviewed-by: Zi Yan <ziy@nvidia.com>
Signed-off-by: David Hildenbrand <david@redhat.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);
 
 	folio->_flags_1 = (folio->_flags_1 & ~0xffUL) | order;
 #ifdef NR_PAGES_IN_LARGE_FOLIO
-- 
2.50.1
Re: [PATCH v1 10/36] mm: sanity-check maximum folio size in folio_set_order()
Posted by Liam R. Howlett 1 month ago 
* David Hildenbrand <david@redhat.com> [250827 18:05]:
> 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().
> 
> Reviewed-by: Zi Yan <ziy@nvidia.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>

Reviewed-by: Liam R. Howlett <Liam.Howlett@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);
>  
>  	folio->_flags_1 = (folio->_flags_1 & ~0xffUL) | order;
>  #ifdef NR_PAGES_IN_LARGE_FOLIO
> -- 
> 2.50.1
> 
>
Re: [PATCH v1 10/36] mm: sanity-check maximum folio size in folio_set_order()
Posted by Lorenzo Stoakes 1 month ago 
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 :)

>
> 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?

>
>  	folio->_flags_1 = (folio->_flags_1 & ~0xffUL) | order;
>  #ifdef NR_PAGES_IN_LARGE_FOLIO
> --
> 2.50.1
>
Re: [PATCH v1 10/36] mm: sanity-check maximum folio size in folio_set_order()
Posted by David Hildenbrand 1 month ago 
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.

-- 
Cheers

David / dhildenb
Re: [PATCH v1 10/36] mm: sanity-check maximum folio size in folio_set_order()
Posted by Lorenzo Stoakes 1 month ago 
On Fri, Aug 29, 2025 at 12:10:30PM +0200, David Hildenbrand wrote:
> 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.

Thanks!

>
> >
> > >
> > > 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.

Ack, ok. I don't think vital for this series though!

>
> --
> Cheers
>
> David / dhildenb
>

Cheers, Lorenzo
Re: [PATCH v1 10/36] mm: sanity-check maximum folio size in folio_set_order()
Posted by Wei Yang 1 month ago 
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().
>
>Reviewed-by: Zi Yan <ziy@nvidia.com>
>Signed-off-by: David Hildenbrand <david@redhat.com>

Reviewed-by: Wei Yang <richard.weiyang@gmail.com>

-- 
Wei Yang
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