linux-kernel - Re: [PATCH] bpf: use FS_USERNS

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Message-Id: <4502642b48f31719673001628df90526071649bc4555c5432d88d2212db3f925@mail.kernel.org>
Date: Thu,  5 Feb 2026 11:20:44 +0000 (UTC)
From: bot+bpf-ci@...nel.org
To: alexander@...alicyn.com,ast@...nel.org
Cc: daniel@...earbox.net,andrii@...nel.org,martin.lau@...ux.dev,eddyz87@...il.com,song@...nel.org,yonghong.song@...ux.dev,john.fastabend@...il.com,kpsingh@...nel.org,sdf@...ichev.me,haoluo@...gle.com,jolsa@...nel.org,jlayton@...nel.org,brauner@...nel.org,bpf@...r.kernel.org,linux-fsdevel@...r.kernel.org,linux-kernel@...r.kernel.org,aleksandr.mikhalitsyn@...urfusion.io,ast@...nel.org,andrii@...nel.org,daniel@...earbox.net,martin.lau@...nel.org,eddyz87@...il.com,yonghong.song@...ux.dev,clm@...a.com,ihor.solodrai@...ux.dev
Subject: Re: [PATCH] bpf: use FS_USERNS_DELEGATABLE for bpffs

> diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
> index 005ea3a2c..c350857b2 100644

[ ... ]

> @@ -1077,7 +1073,7 @@ static struct file_system_type bpf_fs_type = {
>  	.init_fs_context = bpf_init_fs_context,
>  	.parameters	= bpf_fs_parameters,
>  	.kill_sb	= bpf_kill_super,
> -	.fs_flags	= FS_USERNS_MOUNT,
> +	.fs_flags	= FS_USERNS_DELEGATABLE,
>  };

FS_USERNS_DELEGATABLE does not appear to be defined anywhere in the kernel
tree. A search of include/linux/fs.h shows only FS_USERNS_MOUNT is defined
(at line 2268), not FS_USERNS_DELEGATABLE.

The commit message states this flag was "recently introduced", but it is not
present in this codebase. Will this cause a build failure due to an undefined
identifier?

---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/21708956860

AI-authorship-score: low
AI-authorship-explanation: The commit follows standard kernel contribution patterns with natural language and proper references, suggesting human authorship, though the undefined flag error could indicate incomplete context.
issues-found: 1
issue-severity-score: high
issue-severity-explanation: The commit uses FS_USERNS_DELEGATABLE which is not defined in the kernel, causing a build failure that prevents kernel compilation.