Re: [LSF/MM/BPF TOPIC] time to reconsider tracepoints in the vfs?

Al Viro
2025-01-17T02:20:54Z

On Thu, Jan 16, 2025 at 01:43:39PM -0800, Andrii Nakryiko wrote:

> - relative stability of tracepoints in terms of naming, semantics,
> arguments. While not stable APIs, tracepoints are "more stable" in
> practice due to more deliberate and strategic placement (usually), so
> they tend to get renamed or changed much less frequently.
>
> So, as far as BPF is concerned, tracepoints are still preferable to
> kprobes for something like VFS, and just because BPF can be used with
> kprobes easily doesn't mean BPF users don't need useful tracepoints.

The problem is, exact same reasons invite their use by LSM-in-BPF and
similar projects, and once that happens, the rules regarding stability
will bite and bite _hard_.

And from what I've seen from the same LSM-in-BPF folks, it won't stay
within relatively stable areas - not for long, anyway.