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References: <20210610083549.386085-1-aneesh.kumar@linux.ibm.com>
 <20210610083549.386085-6-aneesh.kumar@linux.ibm.com>
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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu, 10 Jun 2021 11:16:12 -0700
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Subject: Re: [PATCH 5/6] mm/mremap: Use pmd/pud_poplulate to update page table
 entries
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
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Cc: Nick Piggin <npiggin@gmail.com>, Linux-MM <linux-mm@kvack.org>,
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On Thu, Jun 10, 2021 at 1:36 AM Aneesh Kumar K.V
<aneesh.kumar@linux.ibm.com> wrote:
>
> @@ -306,8 +306,7 @@ static bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr,
>
>         VM_BUG_ON(!pud_none(*new_pud));
>
> -       /* Set the new pud */
> -       set_pud_at(mm, new_addr, new_pud, pud);
> +       pud_populate(mm, new_pud, (pmd_t *)pud_page_vaddr(pud));
>         flush_tlb_range(vma, old_addr, old_addr + PUD_SIZE);
>         if (new_ptl != old_ptl)
>                 spin_unlock(new_ptl);

That "(pmd_t *)pud_page_vaddr(pud)" looks a bit odd and doesn't match
the pattern.

Should we perhaps have a wrapper for it? Maybe called "pud_pgtable()",
the same way we have pmd_pgtable()?

And that wrapper would be good to have a comment or two about what it
actually is. The same way that pmd_pgtable() should but doesn't ;(

            Linus