Re: WARNING in memory_failure() at include/linux/huge_mm.h:635 triggered

["David Hildenbrand (arm)" <david@kernel.org>]

On 2/4/26 20:48, Zi Yan wrote:
> On 4 Feb 2026, at 14:18, David Hildenbrand (arm) wrote:
> 
>> On 2/4/26 18:41, Zi Yan wrote:
>>>
>>>
>>> More details:
>>> later at sg_vma_fault(), the driver just handles a page fault by supplying
>>> a subpage from a pre-allocated compound page[3]. We then get a large folio
>>> without !CONFIG_TRANSPARENT_HUGEPAGE.
>>
>> We can identify such non-folio (but compound) things by looking at PG_large_rmappable IIRC.
> 
> What do you mean? Changing memory failure code to only handle large_rmappable?
> large_rmappable is a folio flag, memory failure code should see such

Did you mean "should not" ? :)

> non-folio but compound things to begin with, IMHO.

I would say that we could right now reject in memory failure code any 
compound pages that do not have PG_large_rmappable set.

I have the faint recollection that we don't set PG_large_rmappable on 
hugetlb folios yet, so they have to identified as well.

> 
> I think we need to be able to tell between raw page (compound or not),
> mappable page (compound or not, especially for those used with vm_insert_*),
> and folio.

We can't identify (small) folios just yet. We'd need another page flag 
for that (just like PG_large_rmappable), and we all know how that ends ;)

With Willy's work we'll be able to identify folios reliably.

How to deal with that vm_insert_* crap, especially for non-folio pages, 
is also future work based on that.

-- 
Cheers,

David