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

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

[Sun Ke]

This is a regression test for commit 06c4da89c24e
nbd: call genl_unregister_family() first in nbd_cleanup()

Two concurrent processes，one load and unlock nbd module
cyclically, the other one connect and disconnect nbd device cyclically.
Last for 10 seconds.

Signed-off-by: Sun Ke <sunke32@huawei.com>
---
v1->v2: 
1.change install/uninstall to load/unlock
2.use _have_modules instead

 tests/nbd/004     | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 tests/nbd/004.out |  2 ++
 tests/nbd/rc      | 18 ++++++++++++++++++
 3 files changed, 72 insertions(+)
 create mode 100755 tests/nbd/004
 create mode 100644 tests/nbd/004.out

diff --git a/tests/nbd/004 b/tests/nbd/004
new file mode 100755
index 0000000..6b2c5ff
--- /dev/null
+++ b/tests/nbd/004
@@ -0,0 +1,52 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-3.0+
+# Copyright (C) 2022 Sun Ke
+#
+# Regression test for commit 06c4da89c24e
+# nbd: call genl_unregister_family() first in nbd_cleanup()
+
+. tests/nbd/rc
+
+DESCRIPTION="module load/unlock concurrently with connect/disconnect"
+QUICK=1
+
+requires() {
+	_have_modules
+}
+
+module_load_and_unlock() {
+	while true; do
+		modprobe nbd >/dev/null 2>&1
+		modprobe -r nbd >/dev/null 2>&1
+	done
+}
+
+connect_and_disconnect() {
+	while true; do
+		_netlink_connect >/dev/null 2>&1
+		_netlink_disconnect >/dev/null 2>&1
+	done
+}
+
+test() {
+	echo "Running ${TEST_NAME}"
+
+	_start_nbd_server_netlink
+
+	module_load_and_unlock &
+	pid1=$!
+	connect_and_disconnect &
+	pid2=$!
+
+	sleep 10
+	{
+		kill -9 $pid1
+		wait $pid1
+		kill -9 $pid2
+		wait $pid2
+	} 2>/dev/null
+
+	_stop_nbd_server_netlink
+	echo "Test complete"
+}
+
diff --git a/tests/nbd/004.out b/tests/nbd/004.out
new file mode 100644
index 0000000..05ced0c
--- /dev/null
+++ b/tests/nbd/004.out
@@ -0,0 +1,2 @@
+Running nbd/004
+Test complete
diff --git a/tests/nbd/rc b/tests/nbd/rc
index 118553c..b0e7d91 100644
--- a/tests/nbd/rc
+++ b/tests/nbd/rc
@@ -76,3 +76,21 @@ _stop_nbd_server() {
 	rm -f "${TMPDIR}/nbd.pid"
 	rm -f "${TMPDIR}/export"
 }
+
+_start_nbd_server_netlink() {
+	truncate -s 10G "${TMPDIR}/export"
+	nbd-server 8000 "${TMPDIR}/export" >/dev/null 2>&1
+}
+
+_stop_nbd_server_netlink() {
+	killall -SIGTERM nbd-server
+	rm -f "${TMPDIR}/export"
+}
+
+_netlink_connect() {
+	nbd-client localhost 8000 /dev/nbd0 >> "$FULL" 2>&1
+}
+
+_netlink_disconnect() {
+	nbd-client -d /dev/nbd0 >> "$FULL" 2>&1
+}
-- 
2.13.6

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

[Shinichiro Kawasaki]

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
...

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"
 }


> 
> Two concurrent processes，one load and unlock nbd module
> cyclically, the other one connect and disconnect nbd device cyclically.
> Last for 10 seconds.
> 
> Signed-off-by: Sun Ke <sunke32@huawei.com>
> ---
> v1->v2: 
> 1.change install/uninstall to load/unlock

My guess is that Christoph meant "load/unload".

> 2.use _have_modules instead
> 
>  tests/nbd/004     | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  tests/nbd/004.out |  2 ++
>  tests/nbd/rc      | 18 ++++++++++++++++++
>  3 files changed, 72 insertions(+)
>  create mode 100755 tests/nbd/004
>  create mode 100644 tests/nbd/004.out
> 
> diff --git a/tests/nbd/004 b/tests/nbd/004
> new file mode 100755
> index 0000000..6b2c5ff
> --- /dev/null
> +++ b/tests/nbd/004
> @@ -0,0 +1,52 @@
> +#!/bin/bash
> +# SPDX-License-Identifier: GPL-3.0+
> +# Copyright (C) 2022 Sun Ke
> +#
> +# Regression test for commit 06c4da89c24e
> +# nbd: call genl_unregister_family() first in nbd_cleanup()
> +
> +. tests/nbd/rc
> +
> +DESCRIPTION="module load/unlock concurrently with connect/disconnect"
> +QUICK=1
> +
> +requires() {
> +	_have_modules

This helper function needs an argument as the module name to check, nbd.

-- 
Shin'ichiro Kawasaki

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

[Sun Ke]

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
> ...
> 
> 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"
>   }
> 
> 
>>
>> Two concurrent processes，one load and unlock nbd module
>> cyclically, the other one connect and disconnect nbd device cyclically.
>> Last for 10 seconds.
>>
>> Signed-off-by: Sun Ke <sunke32@huawei.com>
>> ---
>> v1->v2:
>> 1.change install/uninstall to load/unlock
> 
> My guess is that Christoph meant "load/unload".
> 
>> 2.use _have_modules instead
>>
>>   tests/nbd/004     | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>>   tests/nbd/004.out |  2 ++
>>   tests/nbd/rc      | 18 ++++++++++++++++++
>>   3 files changed, 72 insertions(+)
>>   create mode 100755 tests/nbd/004
>>   create mode 100644 tests/nbd/004.out
>>
>> diff --git a/tests/nbd/004 b/tests/nbd/004
>> new file mode 100755
>> index 0000000..6b2c5ff
>> --- /dev/null
>> +++ b/tests/nbd/004
>> @@ -0,0 +1,52 @@
>> +#!/bin/bash
>> +# SPDX-License-Identifier: GPL-3.0+
>> +# Copyright (C) 2022 Sun Ke
>> +#
>> +# Regression test for commit 06c4da89c24e
>> +# nbd: call genl_unregister_family() first in nbd_cleanup()
>> +
>> +. tests/nbd/rc
>> +
>> +DESCRIPTION="module load/unlock concurrently with connect/disconnect"
>> +QUICK=1
>> +
>> +requires() {
>> +	_have_modules
> 
> This helper function needs an argument as the module name to check, nbd.
> 

Sorry for missing the reply, I will improve it in v3.

Thanks.
Sun Ke

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

[Sun Ke]

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.

localhost login: [   45.522685] run blktests nbd/004 at 2022-07-19 14:55:21
[   45.622340] debugfs: Directory 'nbd0' with parent 'block' already 
present!
[   45.643911] BUG: kernel NULL pointer dereference, address: 
0000000000000098
[   45.645771] #PF: supervisor write access in kernel mode
[   45.647176] #PF: error_code(0x0002) - not-present page
[   45.648501] PGD 178ebf067 P4D 178ebf067 PUD 17486a067 PMD 0
[   45.649830] Oops: 0002 [#1] PREEMPT SMP
[   45.650732] CPU: 0 PID: 1620 Comm: nbd-client Not tainted 
5.18.0-rc3-00087-g98d40e76652e #4
[   45.652677] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), 
BIOS ?-20190727_073836-buildvm-ppc64le-16.ppc.fedoraproject.org-3.fc31 
04/01/2014
[   45.655724] RIP: 0010:down_write+0x2d/0x90
[   45.656709] Code: 00 00 55 48 89 fd 48 83 05 1f 3e 19 09 01 e8 fa ad 
ff ff 48 83 05 1a 3e 19 09 01 31 c0 ba 01 00 00 00 48 83 05 d3 3c 19 09 
01 <f0> 48 00
[   45.660640] RSP: 0018:ffffc90000663998 EFLAGS: 00010202
[   45.661327] RAX: 0000000000000000 RBX: ffff8881029d03c0 RCX: 
0000000000000000
[   45.662252] RDX: 0000000000000001 RSI: ffffffffbfa44a80 RDI: 
0000000000000098
[   45.663172] RBP: 0000000000000098 R08: 0000000000000000 R09: 
0000000000000228
[   45.664090] R10: 0000000000000150 R11: ffff88817f6da850 R12: 
0000000000000000
[   45.665004] R13: ffff88817f6db00c R14: 0000000000000000 R15: 
ffff88817f6daa00
[   45.665926] FS:  00007f74958f7b40(0000) GS:ffff888237c00000(0000) 
knlGS:0000000000000000
[   45.666962] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   45.667707] CR2: 0000000000000098 CR3: 0000000174850000 CR4: 
00000000000006f0
[   45.668629] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 
0000000000000000
[   45.669548] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 
0000000000000400
[   45.670469] Call Trace:
[   45.670810]  <TASK>
[   45.671098]  start_creating+0xa2/0x1e0
[   45.671601]  debugfs_create_dir+0x1a/0x1e0
[   45.672142]  nbd_start_device+0x153/0x4c0 [nbd]
[   45.672742]  nbd_genl_connect+0x305/0xbd4 [nbd]
[   45.673345]  genl_family_rcv_msg_doit.isra.0+0x102/0x1b0
[   45.674047]  genl_rcv_msg+0xfc/0x2b0
[   45.674521]  ? nbd_genl_reconfigure+0xbe0/0xbe0 [nbd]
[   45.675190]  ? genl_family_rcv_msg_doit.isra.0+0x1b0/0x1b0
[   45.675907]  netlink_rcv_skb+0x62/0x180
[   45.676420]  genl_rcv+0x34/0x60
[   45.676831]  netlink_unicast+0x272/0x5a0
[   45.677344]  netlink_sendmsg+0x3a3/0x6e0
[   45.677846]  ? iovec_from_user+0x60/0x300
[   45.678362]  ? netlink_rcv_skb+0x180/0x180
[   45.678885]  ____sys_sendmsg+0x1da/0x300
[   45.679391]  ? ____sys_recvmsg+0x130/0x220
[   45.679915]  ___sys_sendmsg+0x8e/0xf0
[   45.680394]  ? ___sys_recvmsg+0xa2/0xf0
[   45.680887]  __sys_sendmsg+0x6d/0xe0
[   45.681356]  __x64_sys_sendmsg+0x23/0x30
[   45.681858]  do_syscall_64+0x35/0x80
[   45.682318]  entry_SYSCALL_64_after_hwframe+0x44/0xae
[   45.682960] RIP: 0033:0x7f7494b11b87


> 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"
>   }
> 
> 
>>
>> Two concurrent processes，one load and unlock nbd module
>> cyclically, the other one connect and disconnect nbd device cyclically.
>> Last for 10 seconds.
>>
>> Signed-off-by: Sun Ke <sunke32@huawei.com>
>> ---
>> v1->v2:
>> 1.change install/uninstall to load/unlock
> 
> My guess is that Christoph meant "load/unload".
> 
>> 2.use _have_modules instead
>>
>>   tests/nbd/004     | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>>   tests/nbd/004.out |  2 ++
>>   tests/nbd/rc      | 18 ++++++++++++++++++
>>   3 files changed, 72 insertions(+)
>>   create mode 100755 tests/nbd/004
>>   create mode 100644 tests/nbd/004.out
>>
>> diff --git a/tests/nbd/004 b/tests/nbd/004
>> new file mode 100755
>> index 0000000..6b2c5ff
>> --- /dev/null
>> +++ b/tests/nbd/004
>> @@ -0,0 +1,52 @@
>> +#!/bin/bash
>> +# SPDX-License-Identifier: GPL-3.0+
>> +# Copyright (C) 2022 Sun Ke
>> +#
>> +# Regression test for commit 06c4da89c24e
>> +# nbd: call genl_unregister_family() first in nbd_cleanup()
>> +
>> +. tests/nbd/rc
>> +
>> +DESCRIPTION="module load/unlock concurrently with connect/disconnect"
>> +QUICK=1
>> +
>> +requires() {
>> +	_have_modules
> 
> This helper function needs an argument as the module name to check, nbd.
> 

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

[Shinichiro Kawasaki]

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