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

Jan Kara
2025-01-20T17:15:19Z

On Mon 20-01-25 16:43:31, Christian Brauner wrote:
> > that it's not a big deal. I'm watching with a bit of concern developments
> > like BTF which try to provide some illusion of stability where there isn't
> > much of it. So some tool could spread wide enough without getting regularly
> > broken that breaking it will become a problem. But that is not really the
> > topic of this discussion.
>
> We've stated over and over and will document that we give no stability
> guarantees in that regard.

I'm fully in support of stating that and documenting that because setting
the expectation is important. And I'm also in support of adding tracepoints
to VFS. As Ted wrote, so far both kernel and userspace parts of tracing
were able live along together smoothly (at least from the kernel side ;)).
But I've also heard Linus explicitely saying something along the lines that
if a change in a trace point breaks real users, he's going to revert that
change no matter what you've documented. So we have to take that
possibility into account as well.

Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR