Re: [PATCH v5 3/9] mm/mremap: Use pmd/pud_poplulate to update page table entries
From: Aneesh Kumar K.V <hidden>
Date: 2021-05-20 13:23:32
Also in:
linux-mm
On 5/20/21 6:16 PM, Peter Xu wrote:
On Thu, May 20, 2021 at 01:56:54PM +0530, Aneesh Kumar K.V wrote:quoted
quoted
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?move_page_tables() checks for pmd_trans_huge() and ends up calling move_huge_pmd if it is a THP entry.Sorry to be unclear: what if a huge pud thp?
I am still checking. Looking at the code before commit c49dd340180260c6239e453263a9a244da9a7c85, I don't see kernel handling huge pud thp. I haven't studied huge pud thp enough to understand whether c49dd340180260c6239e453263a9a244da9a7c85 intent to add that support. We can do a move_huge_pud() like we do for huge pmd thp. But I am not sure whether we handle those VMA's earlier and restrict mremap on them? Are huge pud thp only allowed with DAX vmas? -aneesh