Re: [PATCH blktests] nvme/071: test CCR and CQT recovery on a multipath fabrics namespace

[Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>]

On Sep 21, 2026 / 14:59, Mohamed Khalfella wrote:
> nvme/070 demonstrated the ABA ghost write window. The kernel closes it
> by fencing a controller before retrying timed-out writes on another
> path, but nvme/070 does not functionally exercise CCR or CQT
> themselves.
> 
> Add a functional test that drives both cross-controller reset (CCR)
> and command quiesce time (CQT) recovery. The setup is the same as
> nvme/070: a ublk loop device backs an nvmet namespace that is exported
> through two ports, the host connects to both paths, and io_timeout on
> the subsystem drops to 2 seconds. In addition, the target subsystem's
> CQT is set to 30 seconds, since it is disabled by default.
> 
> The first scenario holds one write in the backstore for 4 seconds. The
> host times the write out, starts fencing, and the CCR issued on the
> other path completes within its budget. The second scenario holds a
> write for 10 seconds, longer than CCR can wait, so the host gives up
> on CCR and switches to time-based recovery, waiting out the remaining
> CQT window before releasing the retry.
> 
> Each scenario runs nvme-ghost-write-detector while recovery is in flight
> to check that no stale data surfaces, and confirms the recovery took the
> expected route by watching dmesg after a marker written to /dev/kmsg.
> 
> The test requires nvme_core.multipath=Y and is limited to tcp, rdma
> and fc, the transports that implement controller fencing.
> 
> Signed-off-by: Mohamed Khalfella <mkhalfella@purestorage.com>

Thanks. Overall, this patch looks valuable, and I did not see problems.

As I commented on the dependent series [*], this patch also depends on the
miniublk change. This approach looks useful for this kind of precise test
condition control, but the two points I noted will need consideration.

dmesg_mark() and dmesg_since_mark() can be useful for other future test
cases, and may worth adding to common/rc. Also, it can be refactored with
_dmesg_since_test_start(). Said that, I think current patch is fine and
we can do that refactoring work later.

[*] https://lore.kernel.org/linux-block/arOFG9-sM_GrrbQf@shinmob/