21 Nov
2017
21 Nov
'17
11:05 p.m.
On Tue, 14 Nov 2017 11:56:34 -0800 Dan Williams dan.j.williams@intel.com wrote:
Until there is a solution to the dma-to-dax vs truncate problem it is not safe to allow long standing memory registrations against filesytem-dax vmas. Device-dax vmas do not have this problem and are explicitly allowed.
This is temporary until a "memory registration with layout-lease" mechanism can be implemented for the affected sub-systems (RDMA and V4L2).
Sounds like that will be unpleasant. Do we really need it to be that complex? Can we get away with simply failing the get_user_pages() request? Or are there significant usecases for RDMA and V4L to play with DAX memory?