On Mon, 2023-09-25 at 15:25 -0700, Mike Kravetz wrote:
> On 09/25/23 16:28, riel@xxxxxxxxxxx wrote:
> >
> > -void __unmap_hugepage_range_final(struct mmu_gather *tlb,
> > - struct vm_area_struct *vma, unsigned long
> > start,
> > - unsigned long end, struct page *ref_page,
> > - zap_flags_t zap_flags)
> > +void __hugetlb_zap_begin(struct vm_area_struct *vma,
> > + unsigned long *start, unsigned long *end)
> > {
> > + adjust_range_if_pmd_sharing_possible(vma, start, end);
> > hugetlb_vma_lock_write(vma);
> > i_mmap_lock_write(vma->vm_file->f_mapping);
> > +}
>
> __unmap_hugepage_range_final() was called from unmap_single_vma.
> unmap_single_vma has two callers, zap_page_range_single and
> unmap_vmas.
>
> When the locking was moved into hugetlb_zap_begin, it was only added
> to the
> zap_page_range_single call path. Calls from unmap_vmas are missing
> the
> locking.
Oh, that's a fun one.
I suppose the locking of the f_mapping lock, and calling
adjust_range_if_pmd_sharing_possible matters for the call
from unmap_vmas, while the call tho hugetlb_vma_lock_write
really doesn't matter, since unmap_vmas is called with the
mmap_sem held for write, which already excludes page faults.
I'll add the call there for v4.
Good catch.
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