On Fri, Oct 28, 2022 at 11:11:08AM -0700, Mike Kravetz wrote:
> +struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
> + unsigned long address, unsigned int flags)
> +{
> + struct hstate *h = hstate_vma(vma);
> + struct mm_struct *mm = vma->vm_mm;
> + unsigned long haddr = address & huge_page_mask(h);
> + struct page *page = NULL;
> + spinlock_t *ptl;
> + pte_t *pte, entry;
> +
> + /*
> + * FOLL_PIN is not supported for follow_page(). Ordinary GUP goes via
> + * follow_hugetlb_page().
> + */
> + if (WARN_ON_ONCE(flags & FOLL_PIN))
> + return NULL;
> +
> +retry:
> + pte = huge_pte_offset(mm, haddr, huge_page_size(h));
> + if (!pte)
> + return NULL;
> +
> + ptl = huge_pte_lock(h, mm, pte);
> + entry = huge_ptep_get(pte);
> + if (pte_present(entry)) {
> + page = pte_page(entry) +
> + ((address & ~huge_page_mask(h)) >> PAGE_SHIFT);
> + /*
> + * Note that page may be a sub-page, and with vmemmap
> + * optimizations the page struct may be read only.
> + * try_grab_page() will increase the ref count on the
> + * head page, so this will be OK.
> + *
> + * try_grab_page() should always succeed here, because we hold
> + * the ptl lock and have verified pte_present().
> + */
> + if (WARN_ON_ONCE(!try_grab_page(page, flags))) {
> + page = NULL;
> + goto out;
> + }
> + } else {
> + if (is_hugetlb_entry_migration(entry)) {
> + spin_unlock(ptl);
> + hugetlb_vma_unlock_read(vma);
Just noticed it when pulled the last mm-unstable: this line seems to be a
left-over of v3, while not needed now?
> + __migration_entry_wait_huge(pte, ptl);
> + goto retry;
> + }
> + /*
> + * hwpoisoned entry is treated as no_page_table in
> + * follow_page_mask().
> + */
> + }
> +out:
> + spin_unlock(ptl);
> + return page;
> +}
--
Peter Xu
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