Re: [PATCH RESEND] virtio-pmem: PMEM device spec

[David Hildenbrand <david@redhat.com>]

On 03.08.21 10:26, Cornelia Huck wrote:
> On Fri, Jul 30 2021, Pankaj Gupta <pankaj.gupta.linux@gmail.com> wrote:
>
> > > > +Also, configures a flush callback function with the corresponding region.
> > >
> > > Not sure if that is too specific already... maybe something like "Also,
> > > it configures a notification for when the corresponding region is flushed."?
> >
> > Maybe will remove this line altogether as it is implementation
> > details?
>
> Maybe... I think the point is to configure _something_, not sure if we
> can really generalize that. Other ideas welcome.
>
> > > See above for "flush callback". I'm mostly worrying about the wording
> > > being generic enough (even though it's probably obvious enough for
> > > non-Linux people as well.)
> >
> > yes, Something below is better?
> >
> > The driver MUST not enable any explicit FLUSH on the file memory
> > mapped from the Virtio pmem device
>
> Hm, not sure. Would like to see feedback from others that had worked in
> this area.


I think instead of describing detailed device handling in regard to 
e.g., fsync, we should document what the exact semantics are in POV of 
the driver when issuing a flush, and when it makes sense to issue a 
flush. The device is free to implement that however it likes (fsync, 
whatsoever).

Why do we care about "The driver MUST not enable any explicit FLUSH on 
the file memory mapped from the Virtio pmem device" and what exactly do 
we mean with "explicit FLUSH" here ?

--
Thanks,

David / dhildenb