Re: [PATCH v2 2/5] mm,hugetlb: Sort out folio locking in the faulting path

[Oscar Salvador <osalvador@suse.de>]

On Mon, Jun 23, 2025 at 04:11:38PM +0200, David Hildenbrand wrote:
> > @@ -6801,13 +6810,24 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
> >   		/* Fallthrough to CoW */
> >   	}
> > -	/* hugetlb_wp() requires page locks of pte_page(vmf.orig_pte) */
> > -	folio = page_folio(pte_page(vmf.orig_pte));
> > -	folio_lock(folio);
> > -	folio_get(folio);
> > -
> >   	if (flags & (FAULT_FLAG_WRITE|FAULT_FLAG_UNSHARE)) {
> >   		if (!huge_pte_write(vmf.orig_pte)) {
> > +			/*
> > +			 * Anonymous folios need to be lock since hugetlb_wp()
> > +			 * checks whether we can re-use the folio exclusively
> > +			 * for us in case we are the only user of it.
> > +			 */
> 
> Should we move that comment to hugetlb_wp() instead? And if we are already
> doing this PTL unlock dance now, why not do it in hugetlb_wp() instead so we
> can simplify this code?

Yes, probably we can move it further up.
Let me see how it would look.

thanks! 

-- 
Oscar Salvador
SUSE Labs