On Mon, Jan 30, 2023 at 10:19 AM Ross Zwisler zwisler@chromium.org wrote:
The canonical location for the tracefs filesystem is at /sys/kernel/tracing.
But, from Documentation/trace/ftrace.rst:
Before 4.1, all ftrace tracing control files were within the debugfs file system, which is typically located at /sys/kernel/debug/tracing. For backward compatibility, when mounting the debugfs file system, the tracefs file system will be automatically mounted at:
/sys/kernel/debug/tracing
Many tests in the bpf selftest code still refer to this older debugfs path, so let's update them to avoid confusion.
I wish that was the case, but in reality there are still systems out there where tracefs is only mounted in that old location. For example in one my VMs:
$ cat /proc/mounts |grep tracefs tracefs /sys/kernel/debug/tracing tracefs rw,relatime 0 0 $ ls /sys/kernel/tracing/ $ uname -r 6.2.0-rc5-01030-gc1a3daf7363b
So this change will break the tests. We cannot do it.