Re: [External] Re: [PATCH v2 07/19] mm/hugetlb: Free the vmemmap pages associated with each hugetlb page

[Muchun Song]

On Tue, Oct 27, 2020 at 12:01 AM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
>
> On Mon, Oct 26, 2020 at 10:51:02PM +0800, Muchun Song wrote:
> > +static void split_vmemmap_pmd(pmd_t *pmd, pte_t *pte_p, unsigned long addr)
> > +{
> > +     struct mm_struct *mm = &init_mm;
> > +     struct page *page;
> > +     pmd_t old_pmd, _pmd;
> > +     int i;
> > +
> > +     old_pmd = READ_ONCE(*pmd);
> > +     page = pmd_page(old_pmd);
> > +     pmd_populate_kernel(mm, &_pmd, pte_p);
> > +
> > +     for (i = 0; i < VMEMMAP_HPAGE_NR; i++, addr += PAGE_SIZE) {
> > +             pte_t entry, *pte;
> > +
> > +             entry = mk_pte(page + i, PAGE_KERNEL);
>
> I'd be happier if that were:
>
>         pgprot_t pgprot = PAGE_KERNEL;
> ...
>         for (i = 0; i < VMEMMAP_HPAGE_NR; i++, addr += PAGE_SIZE) {
>                 pte_t entry, *pte;
>
>                 entry = mk_pte(page + i, pgprot);
>                 pgprot = PAGE_KERNEL_RO;
>
> so that all subsequent tail pages are mapped read-only.
>

Good idea, do this can catch some illegal operations. Thanks.


-- 
Yours,
Muchun