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

[Yi Zhang]

Hello

I found random nvme/047 failure on linux-block/for-next when I do
stress blktests nvme/tcp nvme/047 test:

Kernel config: https://pastebin.com/6i3sZWAx
============================================0
nvme/047 (test different queue types for fabric transports)  [failed]
    runtime  71.129s  ...  7.096s
    --- tests/nvme/047.out 2023-07-16 23:04:30.052101710 -0400
    +++ /root/blktests/results/nodev/nvme/047.out.bad 2023-07-19
09:17:35.949908134 -0400
    @@ -1,2 +1,198 @@
     Running nvme/047
    +fio: looks like your file system does not support direct=1/buffered=0
    +fio: looks like your file system does not support direct=1/buffered=0
    +fio: looks like your file system does not support direct=1/buffered=0
    +fio: looks like your file system does not support direct=1/buffered=0
    +fio: destination does not support O_DIRECT
    +fio: destination does not support O_DIRECT
    ...
    (Run 'diff -u tests/nvme/047.out
/root/blktests/results/nodev/nvme/047.out.bad' to see the entire diff)

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

BTW, I also found after disabling nvme_core.multipath, seems this
issue cannot be reproduced.

--
Best Regards,
  Yi Zhang