Re: [bug report] mm: huge_memory: enable debugfs to split huge pages to any order

[Dan Carpenter <dan.carpenter@linaro.org>]

On Thu, Mar 07, 2024 at 09:41:17AM -0500, Zi Yan wrote:
> On 7 Mar 2024, at 9:31, Dan Carpenter wrote:
> 
> > On Thu, Mar 07, 2024 at 09:20:09AM -0500, Zi Yan wrote:
> >>
> >> Can you check if the patch below fixes the issue? I checked the inputs from
> >> debugfs and also inside split_huge_page_to_list_to_order().
> >>
> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> >> index a81a09236c16..4d21e57a7d07 100644
> >> --- a/mm/huge_memory.c
> >> +++ b/mm/huge_memory.c
> >> @@ -3052,6 +3052,9 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list,
> >>         VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
> >>         VM_BUG_ON_FOLIO(!folio_test_large(folio), folio);
> >>
> >> +       if (new_order >= folio_order(folio))
> >> +               return -EINVAL;
> >> +
> >>         /* Cannot split anonymous THP to order-1 */
> >>         if (new_order == 1 && folio_test_anon(folio)) {
> >>                 VM_WARN_ONCE(1, "Cannot split to order-1 folio");
> >
> > From a static analysis perspective I think just this is sufficient?  But
> > I don't really know the code and don't object to the other parts of
> > this path either.
> 
> You are right. The other two changes are in debugfs to avoid unnecessary
> folio locking operations. They are more like an optimization.

Fantastic.  Thanks!

regards,
dan carpenter