linux-kernel - Re: [PATCH v2 4/4] hugetlb/userfaultfd: Unshare all pmds for hugetlbfs when register wp

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Message-ID: <20210218203214.GD108961@xz-x1>
Date:   Thu, 18 Feb 2021 15:32:14 -0500
From:   Peter Xu <peterx@...hat.com>
To:     Axel Rasmussen <axelrasmussen@...gle.com>
Cc:     Linux MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2 4/4] hugetlb/userfaultfd: Unshare all pmds for
 hugetlbfs when register wp

On Thu, Feb 18, 2021 at 10:32:00AM -0800, Axel Rasmussen wrote:
> > @@ -1448,6 +1449,9 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
> >                 vma->vm_flags = new_flags;
> >                 vma->vm_userfaultfd_ctx.ctx = ctx;
> >
> > +               if (is_vm_hugetlb_page(vma) && uffd_disable_huge_pmd_share(vma))
> > +                       hugetlb_unshare_all_pmds(vma);
> 
> This line yields the following error, if building with:
> # CONFIG_CMA is not set
> 
> ./fs/userfaultfd.c:1459: undefined reference to `hugetlb_unshare_all_pmds'

Ouch..  Axel, you mean CONFIG_HUGETLBFS rather than CONFIG_CMA, am I right?

-- 
Peter Xu