On Tue, Nov 21, 2017 at 3:05 PM, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > On Tue, 14 Nov 2017 11:56:34 -0800 Dan Williams <dan.j.williams@xxxxxxxxx> 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? V4L plus DAX is indeed dubious, but RDMA to persistent memory is something the RDMA community is interested in supporting [1]. [1]: http://www.snia.org/sites/default/files/SDC15_presentations/persistant_mem/ChetDouglas_RDMA_with_PM.pdf -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
