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

[Ira Weiny]

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.
> 
> Can we just disable RDMA to regular filesystems? Regular filesystems
> should have full control of the write back and dirty status of their
> pages.

That may be a solution to the corruption/crashes but it is not a solution which
users want to see.  RDMA directly to file systems (specifically DAX) is a use
case we have seen customers ask for.

I think this is the correct path toward supporting this use case.

Ira