Re: [PATCH v5 3/9] mm/mremap: Use pmd/pud_poplulate to update page table entries
From: Peter Xu <peterx@redhat.com>
Date: 2021-05-20 02:18:50
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linux-mm
On Wed, May 19, 2021 at 10:16:07AM +0530, Aneesh Kumar K.V wrote:
quoted
On Thu, Apr 22, 2021 at 11:13:17AM +0530, Aneesh Kumar K.V wrote:quoted
pmd/pud_populate is the right interface to be used to set the respective page table entries. Some architectures like ppc64 do assume that set_pmd/pud_at can only be used to set a hugepage PTE. Since we are not setting up a hugepage PTE here, use the pmd/pud_populate interface.
[1]
quoted hunk ↗ jump to hunk
Can you try this change? modified mm/mremap.c@@ -279,7 +279,7 @@ static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr, pmd_clear(old_pmd); VM_BUG_ON(!pmd_none(*new_pmd)); - pmd_populate(mm, new_pmd, (pgtable_t)pmd_page_vaddr(pmd)); + pmd_populate(mm, new_pmd, pmd_pgtable(pmd)); if (new_ptl != old_ptl) spin_unlock(new_ptl);
I reported this issue today somewhere else: https://lore.kernel.org/linux-mm/YKVemB5DuSqLFmmz@t490s/ (local) And came to this same line after the bisection. This seems to work at least for my userfaultfd test on shmem, however I don't fully understand the commit message [1] on: How do we guarantee we're not moving a thp pte? -- Peter Xu