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    SubjectRe: [PATCH v2 3/5] mm: Fix failure to unmap pte on highmem systems
    On Thu, May 18, 2023 at 12:07:25PM +0100, Ryan Roberts wrote:
    > The loser of a race to service a pte for a device private entry in the
    > swap path previously unlocked the ptl, but failed to unmap the pte. This
    > only affects highmem systems since unmapping a pte is a noop on
    > non-highmem systems.
    >
    > Fixes: 16ce101db85d ("mm/memory.c: fix race when faulting a device private page")
    > Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
    > Reviewed-by: Zi Yan <ziy@nvidia.com>

    Reviewed-by: Mike Rapoport (IBM) <rppt@kernel.org>

    > ---
    > mm/memory.c | 6 ++----
    > 1 file changed, 2 insertions(+), 4 deletions(-)
    >
    > diff --git a/mm/memory.c b/mm/memory.c
    > index f69fbc251198..ed429e20a1bb 100644
    > --- a/mm/memory.c
    > +++ b/mm/memory.c
    > @@ -3728,10 +3728,8 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
    > vmf->page = pfn_swap_entry_to_page(entry);
    > vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
    > vmf->address, &vmf->ptl);
    > - if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte))) {
    > - spin_unlock(vmf->ptl);
    > - goto out;
    > - }
    > + if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte)))
    > + goto unlock;
    >
    > /*
    > * Get a page reference while we know the page can't be
    > --
    > 2.25.1
    >
    >

    --
    Sincerely yours,
    Mike.

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