mm/migrate_device: return number of migrating pages in args->cpages

migrate_vma->cpages originally contained a count of the number of pages
migrating including non-present pages which can be populated directly on
the target.

Commit 241f68859656 ("mm/migrate_device.c: refactor migrate_vma and
migrate_device_coherent_page()") inadvertantly changed this to contain
just the number of pages that were unmapped.  Usage of migrate_vma->cpages
isn't documented, but most drivers use it to see if all the requested
addresses can be migrated so restore the original behaviour.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: 241f68859656 ("mm/migrate_device.c: refactor migrate_vma and migrate_deivce_coherent_page()")
Signed-off-by: Alistair Popple <[email protected]>
Reported-by: Ralph Campbell <[email protected]>
Reviewed-by: Ralph Campbell <[email protected]>
Cc: John Hubbard <[email protected]>
Cc: Alex Sierra <[email protected]>
Cc: Ben Skeggs <[email protected]>
Cc: Felix Kuehling <[email protected]>
Cc: Lyude Paul <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Cc: Michael Ellerman <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions