Re: [PATCH 0/6] RFC v2: mm: gup/dma tracking

[Christopher Lameter]

On Mon, 4 Feb 2019, Jason Gunthorpe wrote:

> On Mon, Feb 04, 2019 at 05:14:19PM +0000, Christopher Lameter wrote:
> > Frankly I still think this does not solve anything.
> >
> > Concurrent write access from two sources to a single page is simply wrong.
> > You cannot make this right by allowing long term RDMA pins in a filesystem
> > and thus the filesystem can never update part of its files on disk.
>
> Fundamentally this patch series is fixing O_DIRECT to not crash the
> kernel in extreme cases.. RDMA has the same problem, but it is much
> easier to hit.

O_DIRECT is the same issue. O_DIRECT addresses always have been in
anonymous memory or special file systems.