Message-ID: <b4d7ce70-3320-4333-9589-b5df187409fe@collabora.com>
Date: Fri, 3 May 2024 18:55:59 +0500
From: Muhammad Usama Anjum <usama.anjum@...labora.com>
To: Yonghong Song <yonghong.song@...ux.dev>,
 Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
 Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau
 <martin.lau@...ux.dev>, Eduard Zingerman <eddyz87@...il.com>,
 Song Liu <song@...nel.org>, John Fastabend <john.fastabend@...il.com>,
 KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...gle.com>,
 Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
 Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>
Cc: Muhammad Usama Anjum <usama.anjum@...labora.com>, kernel@...labora.com,
 linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
 linux-kselftest@...r.kernel.org
Subject: Re: [PATCH bpf-next v3] selftests/bpf: Move test_dev_cgroup to
 prog_tests

On 4/5/24 1:06 AM, Yonghong Song wrote:
> 
> On 4/3/24 5:03 AM, Muhammad Usama Anjum wrote:
>> On 4/3/24 7:36 AM, Yonghong Song wrote:
>>> On 4/2/24 8:16 AM, Muhammad Usama Anjum wrote:
>>>> Yonghong Song,
>>>>
>>>> Thank you so much for replying. I was missing how to run pipeline
>>>> manually.
>>>> Thanks a ton.
>>>>
>>>> On 4/1/24 11:53 PM, Yonghong Song wrote:
>>>>> On 4/1/24 5:34 AM, Muhammad Usama Anjum wrote:
>>>>>> Move test_dev_cgroup.c to prog_tests/dev_cgroup.c to be able to run it
>>>>>> with test_progs. Replace dev_cgroup.bpf.o with skel header file,
>>>>>> dev_cgroup.skel.h and load program from it accourdingly.
>>>>>>
>>>>>>      ./test_progs -t dev_cgroup
>>>>>>      mknod: /tmp/test_dev_cgroup_null: Operation not permitted
>>>>>>      64+0 records in
>>>>>>      64+0 records out
>>>>>>      32768 bytes (33 kB, 32 KiB) copied, 0.000856684 s, 38.2 MB/s
>>>>>>      dd: failed to open '/dev/full': Operation not permitted
>>>>>>      dd: failed to open '/dev/random': Operation not permitted
>>>>>>      #72     test_dev_cgroup:OK
>>>>>>      Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED
>>>>>> Signed-off-by: Muhammad Usama Anjum <usama.anjum@...labora.com>
>>>>>> ---
>>>>>> Changes since v2:
>>>>>> - Replace test_dev_cgroup with serial_test_dev_cgroup as there is
>>>>>>      probability that the test is racing against another cgroup test
>>>>>> - Minor changes to the commit message above
>>>>>>
>>>>>> I've tested the patch with vmtest.sh on bpf-next/for-next and linux
>>>>>> next. It is passing on both. Not sure why it was failed on BPFCI.
>>>>>> Test run with vmtest.h:
>>>>>> sudo LDLIBS=-static PKG_CONFIG='pkg-config --static' ./vmtest.sh
>>>>>> ./test_progs -t dev_cgroup
>>>>>> ./test_progs -t dev_cgroup
>>>>>> mknod: /tmp/test_dev_cgroup_null: Operation not permitted
>>>>>> 64+0 records in
>>>>>> 64+0 records out
>>>>>> 32768 bytes (33 kB, 32 KiB) copied, 0.000403432 s, 81.2 MB/s
>>>>>> dd: failed to open '/dev/full': Operation not permitted
>>>>>> dd: failed to open '/dev/random': Operation not permitted
>>>>>>     #69      dev_cgroup:OK
>>>>>> Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED
>>>>> The CI failure:
>>>>>
>>>>>
>>>>> Error: #72 dev_cgroup
>>>>> serial_test_dev_cgroup:PASS:skel_open_and_load 0 nsec
>>>>> serial_test_dev_cgroup:PASS:cgroup_setup_and_join 0 nsec
>>>>> serial_test_dev_cgroup:PASS:bpf_attach 0 nsec
>>>>> serial_test_dev_cgroup:PASS:bpf_query 0 nsec
>>>>> serial_test_dev_cgroup:PASS:bpf_query 0 nsec
>>>>> serial_test_dev_cgroup:PASS:rm 0 nsec
>>>>> serial_test_dev_cgroup:PASS:mknod 0 nsec
>>>>> serial_test_dev_cgroup:PASS:rm 0 nsec
>>>>> serial_test_dev_cgroup:PASS:rm 0 nsec
>>>>> serial_test_dev_cgroup:FAIL:mknod unexpected mknod: actual 256 !=
>>>>> expected 0
>>>>> serial_test_dev_cgroup:PASS:rm 0 nsec
>>>>> serial_test_dev_cgroup:PASS:dd 0 nsec
>>>>> serial_test_dev_cgroup:PASS:dd 0 nsec
>>>>> serial_test_dev_cgroup:PASS:dd 0 nsec
>>>>>
>>>>> (cgroup_helpers.c:353: errno: Device or resource busy) umount cgroup2
>>>>>
>>>>> The error code 256 means mknod execution has some issues. Maybe you
>>>>> need to
>>>>> find specific errno to find out what is going on. I think you can do ci
>>>>> on-demanding test to debug.
>>>> errno is 2 --> No such file or directory
>>>>
>>>> Locally I'm unable to reproduce it until I don't remove
>>>> rm -f /tmp/test_dev_cgroup_zero such that the /tmp/test_dev_cgroup_zero
>>>> node is present before test execution. The error code is 256 with errno 2.
>>>> I'm debugging by placing system("ls /tmp 1>&2"); to find out which files
>>>> are already present in /tmp. But ls's output doesn't appear on the CI
>>>> logs.
>>> errno 2 means ENOENT.
>>>  From mknod man page (https://linux.die.net/man/2/mknod), it means
>>>    A directory component in/pathname/  does not exist or is a dangling
>>> symbolic link.
>>>
>>> It means /tmp does not exist or a dangling symbolic link.
>>> It is indeed very strange. To make the test robust, maybe creating a temp
>>> directory with mkdtemp and use it as the path? The temp directory
>>> creation should be done before bpf prog attach.
>> I've tried following but still no luck:
>> * /tmp is already present. Then I thought maybe the desired file is already
>> present. I've verified that there isn't file of same name is present inside
>> /tmp.
>> * I thought maybe mknod isn't present in the system. But mknod --help
>> succeeds.
>> * I switched from /tmp to current directory to create the mknod. But the
>> result is same error.
>> * I've tried to use the same kernel config as the BPF CI is using. I'm not
>> able to reproduce it.
>>
>> Not sure which edge case or what's going on. The problem is appearing
>> because of some limitation in the rootfs.
> 
> Maybe you could collect /tmp mount options to see whether anything is
> suspicious? In my vm, I have
>   tmpfs on /tmp type tmpfs (rw,nosuid,nodev,size=3501540k,nr_inodes=1048576)
> and the test works fine.
> 
> 
My test system:
tmpfs /tmp tmpfs rw,relatime 0 0

On the CI, /tmp is present. But it isn't tmpfs. Following shows the logs
from /proc/mounts

On CI:
  /dev/root / 9p
rw,relatime,cache=f,access=client,msize=512000,trans=virtio 0 0
  devtmpfs /dev devtmpfs
rw,relatime,size=1998612k,nr_inodes=499653,mode=755 0 0
  tmpfs /dev/shm tmpfs rw,nosuid,nodev,relatime 0 0
  proc /proc proc rw,nosuid,nodev,noexec,relatime 0 0
  tmpfs /run tmpfs rw,nosuid,nodev,relatime 0 0
  tmpfs /run/netns tmpfs rw,nosuid,nodev,relatime 0 0
  sys /sys sysfs rw,nosuid,nodev,noexec,relatime 0 0
  debugfs /sys/kernel/debug debugfs rw,relatime 0 0
  tracefs /sys/kernel/debug/tracing tracefs rw,relatime 0 0
  cgroup2 /sys/fs/cgroup cgroup2 rw,nosuid,nodev,noexec,relatime 0 0
  tmpfs /sys/fs/cgroup tmpfs rw,relatime 0 0
  net_cls /sys/fs/cgroup/net_cls cgroup rw,relatime,net_cls 0 0
  tmpfs /sys/fs/cgroup tmpfs rw,relatime 0 0
  net_cls /sys/fs/cgroup/net_cls cgroup rw,relatime,net_cls 0 0
  tmpfs /sys/fs/cgroup tmpfs rw,relatime 0 0
  net_cls /sys/fs/cgroup/net_cls cgroup rw,relatime,net_cls 0 0
  bpffs /sys/fs/bpf bpf rw,relatime 0 0
  bpf /sys/fs/bpf bpf rw,relatime 0 0
  tmpfs /mnt tmpfs rw,nosuid,nodev,relatime 0 0
  vmtest-shared /mnt/vmtest 9p
rw,relatime,cache=f,access=client,msize=512000,trans=virtio 0 0
  none /mnt cgroup2 rw,relatime 0 0

-- 
BR,
Muhammad Usama Anjum

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