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SubjectRe: [PATCH 0/1] mm: restore full accuracy in COW page reuse
On Mon 11-01-21 12:05:49, Jason Gunthorpe wrote:
> On Sun, Jan 10, 2021 at 11:26:57PM -0800, John Hubbard wrote:
>
> > So:
> >
> > FOLL_PIN: would use DMA_PIN_COUNTING_BIAS to increment page refcount.
> > These are long term pins for dma.
> >
> > FOLL_GET: would use GUP_PIN_COUNTING_BIAS to increment page refcount.
> > These are not long term pins.
>
> Do we have any places yet that care about the long-term-ness?

I was hoping to use that information to distinguish ephemeral migration
failures due to page reference from long term pins. The later would be a
hard failure for the migration.

--
Michal Hocko
SUSE Labs

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