nvme native multipath question with two physical paths

[Wen Xiong <wenxiong@linux.ibm.com>]

Hi All,

In our nvme native multipath support drawer, each nvme has two physical 
paths/two controllers.
We created a shared namespace on it.

# nvme list-ns /dev/nvme2
[   0]:0x1
# nvme list-ns /dev/nvme6
[   0]:0x1

# ls -l /dev/nvme2*
crw-------. 1 root root 240, 2 Feb 18 18:05 /dev/nvme2
brw-rw----. 1 root disk 259, 4 Feb 18 18:14 /dev/nvme2n1
# ls -l /dev/nvme6*
crw-------. 1 root root 240, 6 Feb 18 18:05 /dev/nvme6

nvme-subsys2 - NQN=nqn.1994-11.com.samsung:nvme:PM1735a:2.5-inch:
\
+- nvme2 pcie 052f:80:00.0 live
+- nvme6 pcie 058f:80:00.0 live

#nvme list
/dev/nvme2n1          /dev/ng2n1


Run stress io test over nvme2n1, we hot unplug nvme2(052f:80:00), 
/dev/nvme2 controller is gone.
/dev/nvme2n1 still existed and io still running over nvme2n1 without 
error. Looks io test still
running over another path(nvme6)bbut we didn’t see /dev/nvme6n1 in /dev 
dir.

# ls -l /dev/nvme2*
brw-rw----. 1 root disk 259, 4 Feb 18 18:22 /dev/nvme2n1
# ls -l /dev/nvme6*
crw-------. 1 root root 240, 6 Feb 18 18:05 /dev/nvme6

With nvme native mpath enable,
- What multipath disk name we should use for ANA nvme multipath?
- Why IO still running over nvme2n1 without error even nvme2 controller 
already unplug?
- Shared namespace is still existed since shared namespace  has another 
controller on it?
- How can let nvme6n1 showing up after nvme2 controller gone.

Thanks for your help!
Wendy