Re: [PATCH v2 1/5] mm,hugetlb: Change mechanism to detect a COW on private mapping

David Hildenbrand
2025-06-25T10:13:21Z

On 25.06.25 09:49, Oscar Salvador wrote:
> On Mon, Jun 23, 2025 at 04:09:51PM +0200, David Hildenbrand wrote:
>>
>>> - /*
>>> - * hugetlb_wp() requires page locks of pte_page(vmf.orig_pte) and
>>> - * pagecache_folio, so here we need take the former one
>>> - * when folio != pagecache_folio or !pagecache_folio.
>>> - */
>>> + /* hugetlb_wp() requires page locks of pte_page(vmf.orig_pte) */
>>> folio = page_folio(pte_page(vmf.orig_pte));
>>> - if (folio != pagecache_folio)
>>> - if (!folio_trylock(folio)) {
>>> - need_wait_lock = 1;
>>> - goto out_ptl;
>>> - }
>>> -
>>> + folio_lock(folio);
>>> folio_get(folio);
>>
>> Just realized that this won't work for this patch here, as we are holding
>> the PTL.
>>
>> In patch #2 you do the right thing.
>
> Yap, missed that.
> I might have to do the lock-unlock-dance here, and then in patch#2 move
> it to hugetlb_wp.
> Sounds reasonable?

Yes

--
Cheers,

David / dhildenb