On Thu, 4 Jun 2020 10:33:41 -0700 Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> wrote: > On Thu, Jun 04, 2020 at 10:40:06AM -0600, David Ahern wrote: > > On 6/4/20 9:48 AM, Jesper Dangaard Brouer wrote: > > > I will NOT send a patch that expose this in uapi/bpf.h. As I explained > > > before, this caused the issues for my userspace application, that > > > automatically picked-up struct bpf_devmap_val, and started to fail > > > (with no code changes), because it needed minus-1 as input. I fear > > > that this will cause more work for me later, when I have to helpout and > > > support end-users on e.g. xdp-newbies list, as it will not be obvious > > > to end-users why their programs map-insert start to fail. I have given > > > up, so I will not NACK anyone sending such a patch. > > Jesper, > > you gave wrong direction to David during development of the patches and > now the devmap uapi is suffering the consequences. > > > > > > > Why is it we need to support file-descriptor zero as a valid > > > file-descriptor for a bpf-prog? > > > > That was a nice property of using the id instead of fd. And the init to > > -1 is not unique to this; adopters of the bpf_set_link_xdp_fd_opts for > > example have to do the same. > > I think it's better to adopt "fd==0 -> invalid" approach. > It won't be unique here. We're already using it in other places in bpf syscall. > I agree with Jesper that requiring -1 init of 2nd field is quite ugly > and inconvenient. Great. If we can remove this requirement of -1 init (and let zero mean feature isn't used), then I'm all for exposing expose in uapi/bpf.h. For future extensions there is still a problem/challenge in dev_map_can_have_prog() that blocks generic-XDP for using future extensions. BUT next person extending devmap can deal with that, so it's not something we need to deal with now. -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer
