Re: [PATCH v3] nvme-rdma: fix ib_device removal race that hangs PCI unbind

[Casey Chen <cachen@purestorage.com>]

On 31/08/2026 16:13, Casey Chen wrote:
> The ->add path is new in this version and has not run on the setup that
> reproduced the hang, so this wants a fresh soak before it is applied.

That soak is done now, so the caveat above no longer applies.

The test bounces both mlx5 interfaces carrying the NVMe-oF RDMA
connections, one at a time, with IO running throughout and a userspace
daemon reconnecting the controllers:

  ethtool -i <iface> | grep bus-info
  echo 1 | sudo tee /sys/bus/pci/devices/<bdf>/remove
  sleep 30
  echo 1 | sudo tee /sys/bus/pci/rescan
  sleep 30

30 iterations over the two interfaces, so 60 remove/rescan cycles, with
60s of settle time between iterations - roughly 90 minutes.

No hang with v3 applied. Every write to remove returned, the interface
came back on the following rescan and the controllers reconnected. The
->add path is covered by this, since each rescan re-probes the HCA as a
new ib_device and so goes through nvme_rdma_add_one().

For contrast, on the same setup without the fix the write to remove
eventually never returns and the task is left in D state with the trace
in the commit message. It is intermittent - most removals complete
normally, and only one that lands while a connect is in flight strands a
controller.