Re: [PATCH bpf-next] bpf: add lookup_and_delete_elem support to hashtab

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Tue, Feb 16, 2021 at 10:00 AM Denis Salopek <denis.salopek@sartura.hr> wrote:
>
> On Mon, Feb 08, 2021 at 09:44:59PM -0800, Andrii Nakryiko wrote:
> > On Wed, Jan 27, 2021 at 9:15 AM Denis Salopek <denis.salopek@sartura.hr> wrote:
> > >
> > > Extend the existing bpf_map_lookup_and_delete_elem() functionality to
> > > hashtab maps, in addition to stacks and queues.
> > > Create a new hashtab bpf_map_ops function that does lookup and deletion
> > > of the element under the same bucket lock and add the created map_ops to
> > > bpf.h.
> > > Add the appropriate test case to 'maps' selftests.
> > >
> > > Signed-off-by: Denis Salopek <denis.salopek@sartura.hr>
> > > Cc: Juraj Vijtiuk <juraj.vijtiuk@sartura.hr>
> > > Cc: Luka Oreskovic <luka.oreskovic@sartura.hr>
> > > Cc: Luka Perkov <luka.perkov@sartura.hr>
> > > ---
> >
> > I think this patch somehow got lost, even though it seems like a good
> > addition. I'd recommend rebasing and re-submitting to let people take
> > a fresh look at this.
> >
> > It would also be nice to have a test_progs test added, not just
> > test_maps. I'd also look at supporting lookup_and_delete for other
> > kinds of hash maps (LRU, per-CPU), so that the support is more
> > complete. Thanks!
> >
>
> Hi Andrii,
>
> I'll also implement the LRU and per-CPU ones and resubmit. I don't quite
> understand the test_progs, what kind of test(s) exactly should I add there?

test_progs is our preferred test runner. It's a collection of
independent tests (sometimes including subtests). See any of the
recently added tests to get a feel for it. test_progs' tests resemble
real-world applications much closer than test_verifier or test_maps
tests, so it serves both as a readable test and as an API demo.

>
> Denis
>
> > >  include/linux/bpf.h                     |  1 +
> > >  kernel/bpf/hashtab.c                    | 38 +++++++++++++++++++++++++
> > >  kernel/bpf/syscall.c                    |  9 ++++++
> > >  tools/testing/selftests/bpf/test_maps.c |  7 +++++
> > >  4 files changed, 55 insertions(+)
> > >
> >
> > [...]