Re: [PATCH bpf-next v3] selftests/bpf: Move test_dev_cgroup to prog_tests

[Yonghong Song]

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@xxxxxxxxxxxxx>
> > > ---
> > > 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