Re: [PATCH] mm/memory_hotplug: fix call folio_test_large with tail page in do_migrate_range

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 25 Mar 2025 20:05:50 +0100 David Hildenbrand <david@redhat.com> wrote:

> On 25.03.25 04:02, Jinjiang Tu wrote:
> > 
> >> Moving that will not make it able to skip the large frozen
> >> (refcount==0, e.g., free hugetlb) folio in the continue/put_folio case
> >> above. Hmmmm ..
> > For free hugetlb, pfn is increased by 1 in each loop. This leads to skip
> > free hugetlb slower.
> 
> Yes. But now I realize that we have the same issue with free buddy pages 
> already (folio_try_get of each individual page :( ).
> 
> >>
> >> We could similarly to dumping folios, snapshot them, so we can read
> >> stable data.
> > extract the code in __dump_page()? But snapshot may lead to
> > do_migrate_range() slower too.
> 
> There is a patch series on the list to do that, but it might take a 
> while to clean that up. Ideally, we'd also jump over free buddy pages. 
> In the future we might have better ways to do that.
> 
> I don't consider this change here really important, but if all it 
> affects is free hugetlb folios, it's not really worth it to have this 
> code around.
> 
> Acked-by: David Hildenbrand <david@redhat.com>
> 
> But: I suspect 8135d8926c08 is not the introducing commit. Please re-verify.
> 
> We should not CC stable.

Why shouldn't we cc:stable?  A userspace-triggerable BUG?