On Tue, Sep 15, 2020 at 1:15 AM Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> wrote: > > On Fri, Sep 11, 2020 at 10:03 AM Borna Cafuk <borna.cafuk@xxxxxxxxxx> wrote: > > > > Hello everyone, > > > > As far as I can see, `map_lookup_and_delete_elem` is implemented only for > > `BPF_MAP_TYPE_QUEUE` and `BPF_MAP_TYPE_STACK` [0]. It might be useful to be > > able to do this operation on other kinds of maps, e.g. `BPF_MAP_TYPE_HASH`. > > > > If I'm not mistaken, it would have benefits over `bpf_map_lookup_elem` followed > > by `bpf_map_delete_elem` in regards to avoiding race conditions. > > Yes, for a case when you know the key. But for the more general > iteration cases, in which you go over all elements, read, and later > remove element, not so much, because removing element would > essentially break iteration. But I do agree, for some cases it should > be quite useful. > > > > > Is there a reason this functionality wasn't implemented? > > Probably no one had a specific use case for this. > > > Is it planned for any time soon? > > > > No, as far as I'm aware. Alright, thank you for the information. > > > I'm looking forward to your input. > > Feel free to implement this and send a patch. It doesn't seem to > impose any extra limitations on use of BPF_MAP_TYPE_HASH, so I don't > see why this can't be done. Great, we'll begin looking into implementing it and submitting a patch. > > > > > Best regards, > > Borna Cafuk > > > > [0] https://elixir.bootlin.com/linux/v5.9-rc4/source/kernel/bpf/syscall.c#L1501
