mm: handle multiple owners of device private pages in migrate_vma

Add a new src_owner field to struct migrate_vma.  If the field is set,
only device private pages with page->pgmap->owner equal to that field are
migrated.  If the field is not set only "normal" pages are migrated.

Fixes: df6ad69838fc ("mm/device-public-memory: device memory cache coherent with CPU")
Link: https://lore.kernel.org/r/20200316193216.920734-3-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Tested-by: Bharata B Rao <bharata@linux.ibm.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 72120061b7d4..3e546cbf03dd 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -196,6 +196,14 @@ struct migrate_vma {
 	unsigned long		npages;
 	unsigned long		start;
 	unsigned long		end;
+
+	/*
+	 * Set to the owner value also stored in page->pgmap->owner for
+	 * migrating out of device private memory.  If set only device
+	 * private pages with this owner are migrated.  If not set
+	 * device private pages are not migrated at all.
+	 */
+	void			*src_owner;
 };
 
 int migrate_vma_setup(struct migrate_vma *args);