The NVMe device I use is a U.2 NVMe ZNS SSD. It has a zoned name space and
a regular name space, and the hang is observed with both name spaces. I have
not yet tried other NVME devices, so I will try them.

See if you can produce this with QEMU NVMe emulation (ZNS and NON-ZNS
mode), if you can then it will be easier to reproduce for everyone.

quoted

FWIW, this is upstream now, so testing with Linus -git would be
preferable.

I see. I have switched from linux-block for-next branch to the upstream branch
of Linus. At git hash 879dbe9ffebc, and still the hang is observed.

--
Best Regards,
Shin'ichiro Kawasaki