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SubjectRe: [PATCH 02/10] mm/hmm: do not erase snapshot when a range is invalidated
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On 1/29/19 8:54 AM, jglisse@redhat.com wrote:
> From: Jérôme Glisse <jglisse@redhat.com>
>
> Users of HMM might be using the snapshot information to do
> preparatory step like dma mapping pages to a device before
> checking for invalidation through hmm_vma_range_done() so
> do not erase that information and assume users will do the
> right thing.
>
> Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Ralph Campbell <rcampbell@nvidia.com>
> Cc: John Hubbard <jhubbard@nvidia.com>
> ---
> mm/hmm.c | 6 ------
> 1 file changed, 6 deletions(-)
>
> diff --git a/mm/hmm.c b/mm/hmm.c
> index b9f384ea15e9..74d69812d6be 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -170,16 +170,10 @@ static int hmm_invalidate_range(struct hmm *hmm, bool device,
>
> spin_lock(&hmm->lock);
> list_for_each_entry(range, &hmm->ranges, list) {
> - unsigned long addr, idx, npages;
> -
> if (update->end < range->start || update->start >= range->end)
> continue;
>
> range->valid = false;
> - addr = max(update->start, range->start);
> - idx = (addr - range->start) >> PAGE_SHIFT;
> - npages = (min(range->end, update->end) - addr) >> PAGE_SHIFT;
> - memset(&range->pfns[idx], 0, sizeof(*range->pfns) * npages);
> }
> spin_unlock(&hmm->lock);
>
>

Seems harmless to me. I really cannot see how this could cause a problem,
so you can add:

Reviewed-by: John Hubbard <jhubbard@nvidia.com>

thanks,
--
John Hubbard
NVIDIA

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