Re: [PATCH] bpf: use FS_USERNS_DELEGATABLE for bpffs

[Daniel Borkmann]

Hi Alexander,

On 2/5/26 12:27 PM, Alexander Mikhalitsyn wrote:
> Am Do., 5. Feb. 2026 um 12:20 Uhr schrieb <bot+bpf-ci@xxxxxxxxxx>:
> > > 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.
If this goes via Christian's vfs tree, it would make sense at least to open a
test PR against https://github.com/kernel-patches/bpf to run this through the
BPF CI with the vfs branch + your patch on top to make sure the tests don't
break.

Thanks,
Daniel