Re: [PATCH 0/1] mm: restore full accuracy in COW page reuse

[Michal Hocko]

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