On Mon, Jan 15, 2024 at 02:49:00PM -0400, Jason Gunthorpe wrote:
> On Wed, Jan 03, 2024 at 05:14:20PM +0800, pet...@redhat.com wrote:
> > diff --git a/mm/gup.c b/mm/gup.c
> > index 63845b3ec44f..760406180222 100644
> > --- a/mm/gup.c
> > +++ b/mm/gup.c
> > @@ -525,6 +525,70 @@ static struct page *no_page_table(struct
> > vm_area_struct *vma,
> > return NULL;
> > }
> >
> > +#ifdef CONFIG_PGTABLE_HAS_HUGE_LEAVES
> > +static struct page *follow_huge_pud(struct vm_area_struct *vma,
> > + unsigned long addr, pud_t *pudp,
> > + int flags, struct follow_page_context *ctx)
> > +{
> > + struct mm_struct *mm = vma->vm_mm;
> > + struct page *page;
> > + pud_t pud = *pudp;
> > + unsigned long pfn = pud_pfn(pud);
> > + int ret;
> > +
> > + assert_spin_locked(pud_lockptr(mm, pudp));
> > +
> > + if ((flags & FOLL_WRITE) && !pud_write(pud))
> > + return NULL;
> > +
> > + if (!pud_present(pud))
> > + return NULL;
> > +
> > + pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT;
> > +
> > +#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
> > + if (pud_devmap(pud)) {
>
> Can this use IS_ENABLED(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD) ?
Sure.
>
> > + /*
> > + * device mapped pages can only be returned if the caller
> > + * will manage the page reference count.
> > + *
> > + * At least one of FOLL_GET | FOLL_PIN must be set, so
> > + * assert that here:
> > + */
> > + if (!(flags & (FOLL_GET | FOLL_PIN)))
> > + return ERR_PTR(-EEXIST);
> > +
> > + if (flags & FOLL_TOUCH)
> > + touch_pud(vma, addr, pudp, flags & FOLL_WRITE);
> > +
> > + ctx->pgmap = get_dev_pagemap(pfn, ctx->pgmap);
> > + if (!ctx->pgmap)
> > + return ERR_PTR(-EFAULT);
> > + }
> > +#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
> > + page = pfn_to_page(pfn);
> > +
> > + if (!pud_devmap(pud) && !pud_write(pud) &&
> > + gup_must_unshare(vma, flags, page))
> > + return ERR_PTR(-EMLINK);
> > +
> > + ret = try_grab_page(page, flags);
> > + if (ret)
> > + page = ERR_PTR(ret);
> > + else
> > + ctx->page_mask = HPAGE_PUD_NR - 1;
> > +
> > + return page;
> > +}
> > +#else /* CONFIG_PGTABLE_HAS_HUGE_LEAVES */
> > +static struct page *follow_huge_pud(struct vm_area_struct *vma,
> > + unsigned long addr, pud_t *pudp,
> > + int flags, struct follow_page_context *ctx)
> > +{
> > + return NULL;
> > +}
> > +#endif /* CONFIG_PGTABLE_HAS_HUGE_LEAVES */
> > +
> > static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long
> > address,
> > pte_t *pte, unsigned int flags)
> > {
> > @@ -760,11 +824,11 @@ static struct page *follow_pud_mask(struct
> > vm_area_struct *vma,
> >
> > pudp = pud_offset(p4dp, address);
> > pud = READ_ONCE(*pudp);
> > - if (pud_none(pud))
> > + if (pud_none(pud) || !pud_present(pud))
> > return no_page_table(vma, flags, address);
>
> Isn't 'pud_none() || !pud_present()' redundent? A none pud is
> non-present, by definition?
Hmm yes, seems redundant. Let me drop it.
>
> > - if (pud_devmap(pud)) {
> > + if (pud_huge(pud)) {
> > ptl = pud_lock(mm, pudp);
> > - page = follow_devmap_pud(vma, address, pudp, flags,
> > &ctx->pgmap);
> > + page = follow_huge_pud(vma, address, pudp, flags, ctx);
> > spin_unlock(ptl);
> > if (page)
> > return page;
>
> Otherwise it looks OK to me
>
> Reviewed-by: Jason Gunthorpe <j...@nvidia.com>
Thanks!
--
Peter Xu
