Re: [PATCH bpf-next 3/4] bpf: Introduce path iterator

[Christian Brauner <brauner@kernel.org>]

On Thu, May 29, 2025 at 11:00:51AM -0700, Song Liu wrote:
> On Thu, May 29, 2025 at 10:38 AM Al Viro <viro@zeniv.linux.org.uk> wrote:
> >
> > On Thu, May 29, 2025 at 09:53:21AM -0700, Song Liu wrote:
> >
> > > Current version of path iterator only supports walking towards the root,
> > > with helper path_parent. But the path iterator API can be extended
> > > to cover other use cases.
> >
> > Clarify the last part, please - call me paranoid, but that sounds like
> > a beginning of something that really should be discussed upfront.
> 
> We don't have any plan with future use cases yet. The only example
> I mentioned in the original version of the commit log is "walk the
> mount tree". IOW, it is similar to the current iterator, but skips non
> mount point iterations.
> 
> Since we call it "path iterator", it might make sense to add ways to
> iterate the VFS tree in different patterns. For example, we may

No, we're not adding a swiss-army knife for consumption by out-of-tree
code. I'm not opposed to adding a sane iterator for targeted use-cases
with a clear scope and internal API behavior as I've said multiple times
already on-list and in-person.

I will not merge anything that will endup exploding into some fancy
"walk subtrees in any order you want".