Re: [PATCH blktests v2] nbd: add a module load and device connect test

[Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>]

On Jul 19, 2022 / 14:47, Sun Ke wrote:
> 
> 
> 在 2022/7/7 20:49, Shinichiro Kawasaki 写道:
> > On Jul 07, 2022 / 11:56, Sun Ke wrote:
> > > This is a regression test for commit 06c4da89c24e
> > > nbd: call genl_unregister_family() first in nbd_cleanup()
> > 
> > Hello Sun, thanks for the patch.
> > 
> > I reverted the commit 06c4da89c24e from the kernel v5.19-rc5 and observed this
> > test case passes. I checked dmesg and saw kernel message below. Kernel did not
> > report the BUG which was noted in the commit 06c4da89c24e. Instead, nbd driver
> > printed out an error "couldn't allocate config".
> > 
> > Jul 07 20:47:01 redsun45q unknown: run blktests nbd/004 at 2022-07-07 20:47:01
> > Jul 07 20:47:01 redsun45q kernel: couldn't allocate config
> > Jul 07 20:47:01 redsun45q kernel: couldn't allocate config
> > Jul 07 20:47:01 redsun45q kernel: couldn't allocate config
> > Jul 07 20:47:01 redsun45q kernel: sysfs: cannot create duplicate filename '/devices/virtual/block/nbd0'
> > Jul 07 20:47:01 redsun45q kernel: CPU: 0 PID: 1043 Comm: modprobe Not tainted 5.19.0-rc5+ #2
> > Jul 07 20:47:01 redsun45q kernel: Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
> > Jul 07 20:47:01 redsun45q kernel: Call Trace:
> > Jul 07 20:47:01 redsun45q kernel:  <TASK>
> > Jul 07 20:47:01 redsun45q kernel:  dump_stack_lvl+0x5b/0x74
> > Jul 07 20:47:01 redsun45q kernel:  sysfs_warn_dup.cold+0x17/0x23
> > ...
> > 
> > or sysfs printed out an warning:
> > 
> > [  366.098479] run blktests nbd/004 at 2022-07-07 21:17:22
> > [  366.747180] sysfs: cannot create duplicate filename '/devices/virtual/block/nbd0'
> > [  366.749653] CPU: 0 PID: 1508 Comm: modprobe Not tainted 5.19.0-rc5+ #2
> > [  366.751680] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebui
> > lt.qemu.org 04/01/2014
> > [  366.755169] Call Trace:
> > [  366.755991]  <TASK>
> > [  366.756722]  dump_stack_lvl+0x5b/0x74
> > [  366.757909]  sysfs_warn_dup.cold+0x17/0x23
> > ...
> > 
> I retry it on commit 98d40e76652e, it can reproduce the Bug.

I see, then some conditions in my environment are hiding the Bug.

> 
> > It would be the better to catch these error and warning message in the test
> > case. For example, following hunk will catch it.
> > 
> > diff --git a/tests/nbd/004 b/tests/nbd/004
> > index 6b2c5ff..9277c10 100755
> > --- a/tests/nbd/004
> > +++ b/tests/nbd/004
> > @@ -47,6 +47,12 @@ test() {
> >          } 2>/dev/null
> > 
> >          _stop_nbd_server_netlink
> > +
> > +       if _dmesg_since_test_start | grep -q -e "couldn't allocate config" \
> > +          -e "cannot create duplicate filename"; then
> > +               echo "Fail"
> > +       fi
> > +
> >          echo "Test complete"
> >   }

Still I think the hunk above adds value to the new test case, since it can catch
the Bug as well as the unexpected kernel messages. I saw you added the hunk to
v3. Thanks.

-- 
Shin'ichiro Kawasaki