Re: [PATCH blktests 0/5] nvme: detect ABA ghost writes on multipath fabrics

[Mohamed Khalfella <mkhalfella@purestorage.com>]

On Wed 2026-09-23 17:18:21 +0900, Shin'ichiro Kawasaki wrote:
> On Sep 16, 2026 / 20:06, Mohamed Khalfella wrote:
> 
> Mohamad, thanks for the series. Before I look in the details of the patches,
> I would like make a comment below.
> 
> > Reproducing the race needs an IO that can be held at the target for
> > longer than the host's io_timeout without being failed. The first three
> > patches give miniublk that ability, since there was previously no way to
> > talk to a running ublk server at all:
> > 
> >   1/5  adds a loopback UDP control channel to the daemon, served by a
> >        detached thread, one reply datagram per request
> >   2/5  adds an INJECT_DELAY command which delays a given number of reads
> >        or writes as an io_uring timeout on the queue's own ring
> >   3/5  exposes it as "miniublk inject", which returns only once the
> >        daemon has armed the delay, so a test can start IO immediately
> >        without racing it
> 
> It is interesting to implement the delay feature to miniublk, and use it as the
> testing tool. But I'm not sure if this is the best approach because of two
> points. First, scsi_debug has jdelay and ndelay options. I wonder if this
> existing feature can fulfill the requirements of the new test case. Second, when
> rublk [*] is available in the PATH of the test system, blktests detect it and
> use it instead of miniublk. I guess the added delay feature is not available in
> rublk, and the test case won't work well. What do you think of these points?
> 

The two points make sense to me. Let me look at scsi_debug delay
injection mechanism first and see if it can be used here. I will also
look at rublk. Thanks for the pointers.