linux-kernel - Re: [PATCH bpf-next v3] selftests/bpf: Move test_dev_cgroup to prog

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Date: Tue, 2 Apr 2024 19:36:25 -0700
From: Yonghong Song <yonghong.song@...ux.dev>
To: Muhammad Usama Anjum <usama.anjum@...labora.com>,
 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: 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 4/2/24 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.

>
>> https://www.kernel.org/doc/Documentation/bpf/bpf_devel_QA.rst
>>