Re: [RFC PATCH] fs: allow opening overlayfs/erofs layers through O_ALT

On Wed, 22 Jul 2026 at 18:36, Andy Lutomirski [off-list ref] wrote:

Other than that question, I think I generally agree with you.  The
interesting operations here (getting an fd to something that was
previously inaccessible) are different enough from normal path lookups
that I think they deserve to be explicit syscalls or syscall modes,
not magic links.

This is a super specialized use case.

I sort of agree that doing statmount() as a syscall was not a bad
idea.   But new syscall for getting a backing layer, that makes sense
on just a couple of filesystems?

And that leaves us with ioctl.   And ioclt() returning an open fd has
it's own problems, besides ioctl being a generally bad interface.

And we have all these powerful concepts and interfaces for
filesystems, why the big resistance to actually using them?.

Sure, it's easy to misuse, but I don't yet see why this particular
case would be a misuse.  Enlighten me please.

Thanks,
Miklos