bpf: Improve bucket_log calculation logic
It was reported that the max_t, ilog2, and roundup_pow_of_two macros have exponential effects on the number of states in the sparse checker. This patch breaks them up by calculating the "nbuckets" first so that the "bucket_log" only needs to take ilog2(). In addition, Linus mentioned: Patch looks good, but I'd like to point out that it's not just sparse. You can see it with a simple make net/core/bpf_sk_storage.i grep 'smap->bucket_log = ' net/core/bpf_sk_storage.i | wc and see the end result: 1 365071 2686974 That's one line (the assignment line) that is 2,686,974 characters in length. Now, sparse does happen to react particularly badly to that (I didn't look to why, but I suspect it's just that evaluating all the types that don't actually ever end up getting used ends up being much more expensive than it should be), but I bet it's not good for gcc either. Fixes: 6ac99e8f ("bpf: Introduce bpf sk local storage") Reported-by:Randy Dunlap <rdunlap@infradead.org> Reported-by:
Luc Van Oostenryck <luc.vanoostenryck@gmail.com> Suggested-by:
Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by:
Martin KaFai Lau <kafai@fb.com> Signed-off-by:
Daniel Borkmann <daniel@iogearbox.net> Reviewed-by:
Luc Van Oostenryck <luc.vanoostenryck@gmail.com> Link: https://lore.kernel.org/bpf/20200207081810.3918919-1-kafai@fb.com
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