[bug report] blktests nvme/047 failed due to /dev/nvme0n1 not created in time

[Daniel Wagner]

On Fri, Aug 04, 2023 at 06:33:04PM +0800, Yi Zhang wrote:
> On Tue, Aug 1, 2023 at 7:28 PM Yi Zhang <yi.zhang at redhat.com> wrote:
> > After some investigating, I found it was due to the /dev/nvme0n1 node
> > couldn't be created in time which lead to the following fio failing.
> > + nvme connect -t tcp -a 127.0.0.1 -s 4420 -n blktests-subsystem-1
> > --hostnqn=nqn.2014-08.org.nvmexpress:uuid:0f01fb42-9f7f-4856-b0b3-51e60b8de349
> > --hostid=0f01fb42-9f7f-4856-b0b3-51e60b8de349 --nr-write-queues=1
> > + ls -l /dev/nvme0 /dev/nvme-fabrics
> > crw-------. 1 root root 234,   0 Aug  1 05:50 /dev/nvme0
> > crw-------. 1 root root  10, 122 Aug  1 05:50 /dev/nvme-fabrics
> > + '[' '!' -b /dev/nvme0n1 ']'
> > + echo '/dev/nvme0n1 node still not created'
> > dmesg:
> > [ 1840.413396] loop0: detected capacity change from 0 to 10485760
> > [ 1840.934379] nvmet: adding nsid 1 to subsystem blktests-subsystem-1
> > [ 1841.018766] nvmet_tcp: enabling port 0 (127.0.0.1:4420)
> > [ 1846.782615] nvmet: creating nvm controller 1 for subsystem
> > blktests-subsystem-1 for NQN
> > nqn.2014-08.org.nvmexpress:uuid:0f01fb42-9f7f-4856-b0b3-51e60b8de349.
> > [ 1846.808392] nvme nvme0: creating 33 I/O queues.
> > [ 1846.874298] nvme nvme0: mapped 1/32/0 default/read/poll queues.
> > [ 1846.945334] nvme nvme0: new ctrl: NQN "blktests-subsystem-1", addr
> > 127.0.0.1:4420

Not really sure how the blk device registration code works, but this
looks like there something executed not in the same context as the
nvme-cli command and thus we might return to userspace before the device
is fully created. And there is also udev events which are handled by
systemd. If this is the case, we might want to add some generic helper
which waits for the device to pop up before we continue with the test.