Re: [Nbd] [RESEND][PATCH 0/5] nbd improvements

On Thu, Sep 15, 2016 at 02:01:59PM +0200, Wouter Verhelst wrote:

Yes. There was some discussion on that part, and we decided that setting
the flag doesn't hurt, but the spec also clarifies that using it on READ
does nothing, semantically.


The problem is that there are clients in the wild which do set it on
READ, so it's just a matter of "be liberal in what you accept".

Note that FUA on READ in SCSI and NVMe does have a meaning - it
requires you to bypass any sort of cache on the target.  I think it's an
wrong defintion because it mandates implementation details that aren't
observable by the initiator, but it's still the spec wording and nbd
diverges from it.  That's not nessecarily a bad thing, but a caveat to
look out for.