> When get_user_pages_fast() is called before try_to_unmap(), > direct I/O code increments refcount on the target page. > Because this refcount is not associated to the mapping, > migration code will find remaining refcounts after try_to_unmap() > unmaps all mappings. Then refcount check decides migration to fail, > so direct I/O is continued safely. This would imply that direct IO can make migration fail arbitarily. Also not good. Should we add some retries, at least for the soft offline case? -Andi -- ak@xxxxxxxxxxxxxxx -- Speaking for myself only. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>