On 2025-10-27 03:04, Pavel Begunkov wrote:

On 10/26/25 17:34, David Wei wrote:

quoted

Rename lock_two_rings() to io_lock_two_rings() and export. This will be
used when sharing a src ifq owned by one ring with another ring. During
this process both rings need to be locked in a deterministic order,
similar to the current user io_clone_buffers().

unlock();
double_lock();

It's quite a bad pattern just like any temporary unlocks in the
registration path, it gives a lot of space for exploitation.

Ideally, it'd be

lock(ctx1);
zcrx = grab_zcrx(ctx1, id); // with some refcounting inside
unlock(ctx1);

lock(ctx2);
install(ctx2, zcrx);
unlock(ctx2);

Thanks, I've refactored this to lock rings in sequence instead of both
rings.

And as discussed, we need to think about turning it into a temp
file, bc of sync, and it's also hard to send an io_uring fd.
Though, that'd need moving bits around to avoid refcounting
cycles.

My next version of this adds a refcount to ifq and decouple its lifetime
from ring ctx as a first step. Could we defer turning ifq into a file as
a follow up?