linux-kernel - Re: [PATCH v5 6/7] btf: Add lazy sorting validation for binary search

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Message-ID: <854a2c2ceaa52f1ad26fb803d1ad5668fd3200b3.camel@gmail.com>
Date: Mon, 10 Nov 2025 12:44:21 -0800
From: Eduard Zingerman <eddyz87@...il.com>
To: Donglin Peng <dolinux.peng@...il.com>, Alexei Starovoitov	
 <alexei.starovoitov@...il.com>, Andrii Nakryiko
 <andrii.nakryiko@...il.com>,  Ihor Solodrai <ihor.solodrai@...ux.dev>
Cc: bot+bpf-ci@...nel.org, Alexei Starovoitov <ast@...nel.org>, 
	zhangxiaoqin@...omi.com, LKML <linux-kernel@...r.kernel.org>, bpf	
 <bpf@...r.kernel.org>, Alan Maguire <alan.maguire@...cle.com>, Song Liu	
 <song@...nel.org>, pengdonglin <pengdonglin@...omi.com>, Andrii Nakryiko	
 <andrii@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Martin KaFai
 Lau	 <martin.lau@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>,
 Chris Mason	 <clm@...a.com>
Subject: Re: [PATCH v5 6/7] btf: Add lazy sorting validation for binary
 search

On Mon, 2025-11-10 at 09:42 +0800, Donglin Peng wrote:

[...]

> [[Resending in plain text format - previous HTML email was rejected]
> 
> Thanks for the feedback. Based on the previous discussions, I plan
> to implement the following changes in the next version:
> 
> 1. Modify the btf__permute interface to adopt the ID map approach, as
>     suggested by Andrii.
> 
> 2. Remove the lazy sort check and move the verification to the BTF
>     parsing phase. This addresses two concerns: potential race conditions
>     with write operations and const-cast issues. The overhead is negligible
>      (approximately 1.4ms for vmlinux BTF).
> 
> 3. Invoke the btf__permute interface to implement BTF sorting in resolve_btfids.
> 
> I welcome any further suggestions.

Hi Donglin,

I think this summarizes the discussion pretty well.
One thing to notice about (2): if sorting is done by resolve_btfids,
there is no need to check for BTF being sorted in vmlinux BTF.
So, maybe it's a good idea to skip this check for it, as Alexei suggested
(but not for programs BTF).

Thanks,
Eduard.