Re: [PATCH RFC 00/10] RDMA/FS DAX truncate proposal

[Jason Gunthorpe]

On Wed, Jun 12, 2019 at 03:54:19PM -0700, Dan Williams wrote:
> > > My preference would be to avoid this scenario, but if it is really
> > > necessary, we could probably build it with some work.
> > >
> > > The only case we use it today is forced HW hot unplug, so it is rarely
> > > used and only for an 'emergency' like use case.
> >
> > I'd really like to avoid this as well.  I think it will be very confusing for
> > RDMA apps to have their context suddenly be invalid.  I think if we have a way
> > for admins to ID who is pinning a file the admin can take more appropriate
> > action on those processes.   Up to and including killing the process.
> 
> Can RDMA context invalidation, "device disassociate", be inflicted on
> a process from the outside? 

Yes, but it is currently only applied to the entire device - ie you do
'rmmod mlx5_ib' and all the running user space process see that their
FD has moved to some error and the device is broken.

Targetting the disassociate of only a single FD would be a new thing.

Jason