Re: [PATCH v2 01/20] hugetlb: Don't restore vmemmap of non-HVOed folios on bulk restore error

[Muchun Song <muchun.song@linux.dev>]

> On Oct 22, 2026, at 10:17, Muchun Song <muchun.song@linux.dev> wrote:
> 
> 
> 
>> On Oct 22, 2026, at 05:27, James Houghton <jthoughton@google.com> wrote:
>> 
>> On Wed, Oct 21, 2026 at 2:33 AM Muchun Song <muchun.song@linux.dev> wrote:
>>>> On Oct 3, 2026, at 08:21, James Houghton <jthoughton@google.com> wrote:
>>>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>>>> index a1b51251103b..4dac7ed1df57 100644
>>>> --- a/mm/hugetlb.c
>>>> +++ b/mm/hugetlb.c
>>>> @@ -1613,9 +1613,14 @@ static void bulk_vmemmap_restore_error(struct hstate *h,
>>>>             * page is made a surplus page and removed from the list.
>>>>             * If are able to restore vmemmap and free one hugetlb page, we
>>>>             * quit processing the list to retry the bulk operation.
>>>> +             *
>>>> +             * Folios whose vmemmap was never optimized (e.g. because HVO
>>>> +             * failed when they were allocated) can be freed right away;
>>>> +             * remove_hugetlb_folio() has already cleared their hugetlb flag.
>>> 
>>> Since you mentioned the hugetlb flag is cleared. So it's unnecessary to clear it again.
>>> 
>>>>             */
>>>>             list_for_each_entry_safe(folio, t_folio, folio_list, lru)
>>>> -                     if (hugetlb_vmemmap_restore_folio(h, folio)) {
>>>> +                     if (folio_test_hugetlb_vmemmap_optimized(folio) &&
>>>> +                         hugetlb_vmemmap_restore_folio(h, folio)) {
>>>>                             list_del(&folio->lru);
>>>>                             spin_lock_irq(&hugetlb_lock);
>>>>                             add_hugetlb_folio(h, folio, true);
>>> 
>>> Something like following:
>>> 
>>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>>> index 6a011b627986..1ab3e61f4704 100644
>>> --- a/mm/hugetlb.c
>>> +++ b/mm/hugetlb.c
>>> @@ -1616,21 +1616,31 @@ static void bulk_vmemmap_restore_error(struct hstate *h,
>>>                * If are able to restore vmemmap and free one hugetlb page, we
>>>                * quit processing the list to retry the bulk operation.
>>>                */
>>> -               list_for_each_entry_safe(folio, t_folio, folio_list, lru)
>>> -                       if (hugetlb_vmemmap_restore_folio(h, folio)) {
>>> -                               list_del(&folio->lru);
>>> +               list_for_each_entry_safe(folio, t_folio, folio_list, lru) {
>>> +                       list_del(&folio->lru);
>>> +
>>> +                       /*
>>> +                        * remove_hugetlb_folio() already cleared the hugetlb flag
>>> +                        * for folios whose vmemmap was not optimized, so they can
>>> +                        * be freed without restoring vmemmap.
>>> +                        */
>>> +                       if (folio_test_hugetlb(folio) &&
>>> +                           hugetlb_vmemmap_restore_folio(h, folio)) {
>>>                               spin_lock_irq(&hugetlb_lock);
>>>                               add_hugetlb_folio(h, folio, true);
>>>                               spin_unlock_irq(&hugetlb_lock);
>>> -                       } else {
>>> -                               list_del(&folio->lru);
>>> +                               continue;
>>> +                       }
>>> +
>>> +                       if (folio_test_hugetlb(folio)) {
>>>                               spin_lock_irq(&hugetlb_lock);
>>>                               __folio_clear_hugetlb(folio);
>>>                               spin_unlock_irq(&hugetlb_lock);
>>> -                               update_and_free_hugetlb_folio(h, folio, false);
>>> -                               cond_resched();
>>> -                               break;
>>>                       }
>>> +                       update_and_free_hugetlb_folio(h, folio, false);
>>> +                       cond_resched();
>>> +                       break;
>>> +               }
>>>       }
>>> }
>> 
>> Thanks, Muchun. :) I think it's slightly easier to read without the second
>> folio_test_hugetlb(), like this:

Hi James,

Could you send it as a separate fix patch so that we could merge it first?

Thanks.

> 
> More clear, LGTM.
> 
> Thanks,
> Muchun