Enable tracing only for one function and its children?

[Timur Tabi]

Is there a way to enable ftrace tracing only for one specific function
and all the functions it calls?  Then when the function returns,
disable tracing until the next time?

When I pass the function name only to set_ftrace_filter, it literally
only traces that function, which doesn't help me.  I tried setting
writing "nvidia_ioctl:traceon" to set_ftrace_filter, but that just
gave me an "invalid argument" error.  And even if that did work, I
don't know what function to use for :traceoff.