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The tc_redirect umounts /sys in the new namespace, which can be mounted as shared and cause global umount. The lazy umount also takes down mounted trees under /sys like debugfs, which won't be available after sysfs mounts again and could cause fails in other tests. # cat /proc/self/mountinfo | grep debugfs 34 23 0:7 / /sys/kernel/debug rw,nosuid,nodev,noexec,relatime shared:14 - debugfs debugfs rw # cat /proc/self/mountinfo | grep sysfs 23 86 0:22 / /sys rw,nosuid,nodev,noexec,relatime shared:2 - sysfs sysfs rw # mount | grep debugfs debugfs on /sys/kernel/debug type debugfs (rw,nosuid,nodev,noexec,relatime) # ./test_progs -t tc_redirect #164 tc_redirect:OK Summary: 1/4 PASSED, 0 SKIPPED, 0 FAILED # mount | grep debugfs # cat /proc/self/mountinfo | grep debugfs # cat /proc/self/mountinfo | grep sysfs 25 86 0:22 / /sys rw,relatime shared:2 - sysfs sysfs rw Making the sysfs private under the new namespace so the umount won't trigger the global sysfs umount. Reported-by: Hangbin Liu <haliu@redhat.com> Signed-off-by: Jiri Olsa <jolsa@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Cc: Jussi Maki <joamaki@gmail.com> Link: https://lore.kernel.org/bpf/20220104121030.138216-1-jolsa@kernel.org
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.