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

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Message-ID: <CAJqdLrqRBhmrQQA0MA9f5Js6rTZkJFf6-=KT+eZahakgX4_3fw@mail.gmail.com>
Date: Thu, 5 Feb 2026 12:27:09 +0100
From: Alexander Mikhalitsyn <alexander@...alicyn.com>
To: bot+bpf-ci@...nel.org
Cc: ast@...nel.org, 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, 
	martin.lau@...nel.org, clm@...a.com, ihor.solodrai@...ux.dev
Subject: Re: [PATCH] bpf: use FS_USERNS_DELEGATABLE for bpffs

Am Do., 5. Feb. 2026 um 12:20 Uhr schrieb <bot+bpf-ci@...nel.org>:
>
> > 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?

Yeah, this should be applied on top of
https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git/commit/?h=vfs-7.0.misc&id=269c46e936f3b5f2b6b567ca124d5f5ea07a371c
in vfs/vfs-7.0.misc I think.

>
>
> ---
> 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.