Messages in this thread | | | From | Daniel Colascione <> | Date | Mon, 30 Jul 2018 03:25:43 -0700 | Subject | Re: [PATCH v3] Add BPF_SYNCHRONIZE_MAP_TO_MAP_REFERENCES bpf(2) command |
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On Mon, Jul 30, 2018 at 3:04 AM, Daniel Borkmann <daniel@iogearbox.net> wrote: > Hmm, I don't think such UAPI as above is future-proof. In case we would want > a similar mechanism in future for other maps, we would need a whole new bpf > command or reuse BPF_SYNCHRONIZE_MAP_TO_MAP_REFERENCES as a workaround though > the underlying map may not even be a map-to-map. Additionally, we don't have > any map object at hand in the above, so we couldn't make any finer grained > decisions either. Something like below would be more suitable and leaves room > for extending this further in future.
YAGNI. Your proposed mechanism doesn't add anything under the current implementation. It's also not clear how a map-specific synchronization command is supposed to work in cases where we swap multiple map references. Do we synchronize_rcu multiple times? Why would we impose that inefficiency just for the sake of some non-specific future extensibility? Add some kind of batching layer? The current approach works for the anticipated use cases.
While my preference is not to talk about map-to-maps at all in the user API and instead spec the thing as talking about map references in general, I'd rather have something that talks about references-to-maps-acquired-from-maps than this interface.
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