Re: [PATCH] ovl: add ioctls to retrieve layer file descriptors

Miklos Szeredi <[email protected]> Wed, 8 Jul 2026 16:08:56 +0200

Newsgroups	org.kernel.vger.linux-unionfs,org.kernel.vger.linux-api,org.kernel.vger.linux-fsdevel
Message-ID	<CAJfpegvQ06=2E0V_ADgxwmo7e5weTfOMozmBB-QVNLLWYAm8WQ@mail.gmail.com>

On Wed, 8 Jul 2026 at 14:27, Giuseppe Scrivano <[email protected]> wrote:

> is there any existing user of such a mechanism?  I don't see any mount
> specific info under /proc or /sys.

Not yet, but I think it would be good to have one.  It's definitely a
bigger bite than adding an ioctl(), though.

> >> OVL_IOC_GET_LAYERS_INFO: copy a struct ovl_layers_info to userspace
> >>                         with numlower, numlowerdata, and has_upper.
> >
> > Isn't this info obtainable via statmount(2) already?  If not, it
> > should be there, instead of a specialized ioctl.
>

> no that is not exposed by statmount

I mean, you should be able to get that info by counting the lowerdir+,
datadir+ and upperdir options, no?

Thanks,
Miklos