Re: [PATCH RFC 00/10] RDMA/FS DAX truncate proposal
From: Jason Gunthorpe
Date: Wed Jun 12 2019 - 07:52:00 EST
On Wed, Jun 12, 2019 at 12:29:17PM +0200, Jan Kara wrote:
> > > The main objection to the current ODP & DAX solution is that very
> > > little HW can actually implement it, having the alternative still
> > > require HW support doesn't seem like progress.
> > >
> > > I think we will eventually start seein some HW be able to do this
> > > invalidation, but it won't be universal, and I'd rather leave it
> > > optional, for recovery from truely catastrophic errors (ie my DAX is
> > > on fire, I need to unplug it).
> > Agreed. I think software wise there is not much some of the devices can do
> > with such an "invalidate".
> So out of curiosity: What does RDMA driver do when userspace just closes
> the file pointing to RDMA object? It has to handle that somehow by aborting
> everything that's going on... And I wanted similar behavior here.
It aborts *everything* connected to that file descriptor. Destroying
everything avoids creating inconsistencies that destroying a subset
What has been talked about for lease break is not destroying anything
but very selectively saying that one memory region linked to the GUP
is no longer functional.