Re: [RFC PATCH bpf-next v2 2/2] selftests/bpf: add tests for selective kmod BTF loading

On 8/13/2026 11:37 AM, [email protected] wrote:
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [Medium] The tracking counter `obj->kmod_btfs->nr_loaded` is never updated, rendering the early termination optimization for BTF loading completely ineffective.
> --
> 
> --- Patch [2]: [RFC PATCH bpf-next v2 2/2] selftests/bpf: add tests for selective kmod BTF loading ---
> commit 506359525a106f517e013e060ee2c6feb17720c8
> Author: Fuyu Zhao <[email protected]>
> 
> selftests/bpf: add tests for selective kmod BTF loading
> 
> Add test cases to verify the new ".kmod_btfs" section logic in libbpf.
> The added test cases cover three main scenarios: valid module, non-existent
> module, and duplicates/unneeded modules.
> 
>> diff --git a/tools/testing/selftests/bpf/prog_tests/kmod_btfs.c b/tools/testing/selftests/bpf/prog_tests/kmod_btfs.c
>> index 0000000000000..d875fcce6681d
>> --- /dev/null
>> +++ b/tools/testing/selftests/bpf/prog_tests/kmod_btfs.c
>> @@ -0,0 +1,52 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +#include <test_progs.h>
>> +#include "kmod_btfs.skel.h"
>> +#include "kmod_btfs_nonexist.skel.h"
>> +#include "kmod_btfs_mix.skel.h"
>> +
> 
> [ ... ]
> 
> [Severity: Medium]
> While reviewing these tests, I noticed a potential regression in the libbpf
> code they exercise. In load_module_btfs():
> 
> tools/lib/bpf/libbpf.c:load_module_btfs() {
> ...
> 		if (obj->kmod_btfs &&
> 		    obj->kmod_btfs->nr_names == obj->kmod_btfs->nr_loaded)
> 			break;
> ...
> }
> 
> Is obj->kmod_btfs->nr_loaded ever incremented when a module BTF is
> successfully loaded?
> 
> If it is not incremented, will this early termination condition ever be
> met? It appears this might unnecessarily iterate over all remaining
> system BTFs, which would bypass the intended performance optimization
> of the .kmod_btfs section.
> 

Thanks for catching this. This is the same oversight mentioned above.
I'll fix the nr_loaded accounting in v3.