linux-kernel - Re: [RFC PATCH v4 1/7] libbpf: Extract BTF type remapping logic into helper function

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Message-ID: <61e92756ea7f202f2e501747b574e97b2f5bc32f.camel@gmail.com>
Date: Tue, 04 Nov 2025 16:36:09 -0800
From: Eduard Zingerman <eddyz87@...il.com>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>, Donglin Peng
	 <dolinux.peng@...il.com>
Cc: ast@...nel.org, linux-kernel@...r.kernel.org, bpf@...r.kernel.org, Alan
 Maguire <alan.maguire@...cle.com>, Song Liu <song@...nel.org>, pengdonglin
 <pengdonglin@...omi.com>
Subject: Re: [RFC PATCH v4 1/7] libbpf: Extract BTF type remapping logic
 into helper function

On Tue, 2025-11-04 at 16:11 -0800, Andrii Nakryiko wrote:

[...]

> > @@ -3400,6 +3400,37 @@ int btf_ext__set_endianness(struct btf_ext *btf_ext, enum btf_endianness endian)
> >         return 0;
> >  }
> > 
> > +static int btf_remap_types(struct btf *btf, struct btf_ext *btf_ext,
> > +                          btf_remap_type_fn visit, void *ctx)
> 
> tbh, my goal is to reduce the amount of callback usage within libbpf,
> not add more of it...
> 
> I don't like this refactoring. We should convert
> btf_ext_visit_type_ids() into iterators, have btf_field_iter_init +
> btf_field_iter_next usable in for_each() form, and not try to reuse 5
> lines of code. See my comments in the next patch.

Remapping types is a concept.
I hate duplicating code for concepts.
Similarly, having patch #3 == patch #5 and patch #4 == patch #6 is
plain ugly. Just waiting for a bug because we changed the one but
forgot to change another in a year or two.

[...]