Re: [PATCH 0/3] Fix some issues when looking up hugetlb page

[Mike Kravetz <mike.kravetz@oracle.com>]

On 08/19/22 18:12, Baolin Wang wrote:
> Hi,
> 
> On ARM64 architecture, it can support CONT-PTE/PMD size hugetlb. When
> looking up hugetlb page by follow_page(), we will hold the incorrect
> pte/pmd lock for the CONT-PTE/PMD size hugetlb page, which will make
> the pte/pmd entry unstable even under the lock and cause some potential
> race issues. So considering the CONT-PTE/PMD size hugetlb, this patch set
> changes to use the correct function to get the correct pte/pmd entry lock
> to make the pte/pmd entry stable.

Thank you for looking at this.

I often get confused by arm64 CONT-PTE/PMD layout, so my understanding may be
wrong.  Can we use the PMD page lock for locking both CONT-PTE and CONT-PMD
entries?  Again, I may be confused by the CONT-* page table layout, but it
seems these would all be referenced via that same PMD page of the page table.
Or, perhaps CONT-PMD can span multiple PMD pages?

If we can use PMD page for locking, this would be much finer grain that
lock in the mm.
-- 
Mike Kravetz