On Mon, Mar 16, 2020 at 06:52:58PM +0100, Christoph Hellwig wrote:

Add a new opaque owner field to struct dev_pagemap, which will allow the hmm and migrate_vma code to identify who owns ZONE_DEVICE memory, and refuse to work on mappings not owned by the calling entity.

Using a pointer seems like a good solution to me.

Is this a bug fix? What is the downside for migrate on pages it doesn't work? I'm not up to speed on migrate..

Jason