Re: file handle in statx (was: Re: How to cope with subvolumes and snapshots on muti-user systems?)

Miklos Szeredi
2023-12-12T09:43:12Z

On Tue, 12 Dec 2023 at 10:35, Christian Brauner <brauner@kernel.org> wrote:

> So taking a step back here, please. The original motivation for this
> discussion was restricted to handle btrfs - and now bcachefs as well.
> Both have a concept of a subvolume so it made sense to go that route.
> IOW, it wasn't originally a generic problem or pitched as such.
>
> Would overlayfs be able to utilize an extended inode field as well?

Well, yes, but I don't think that's the right solution.

I think the right solution is to move to using file handles instead of
st_ino, the problem with that is that there's no way kernel can force
upgrading userspace.

It might help to have the fh in statx, since that's easier on the
userspace programmer than having to deal with two interfaces (i_ino
won't go away for some time, because of backward compatibility).
OTOH I also don't like the way it would need to be shoehorned into
statx.

Thanks,
Miklos