Instead of putting io_uring's registered files in unix_gc() we want it
to be done by io_uring itself. The trick here is to consider io_uring
registered files for cycle detection but not actually putting them down.
Because io_uring can't register other ring instances, this will remove
all refs to the ring file triggering the ->release path and clean up
with io_ring_ctx_free().

Cc: stable@vger.kernel.org
Fixes: 6b06314c ("io_uring: add file set registration")
Reported-and-tested-by: NDavid Bouman <dbouman03@gmail.com>
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NThadeu Lima de Souza Cascardo <cascardo@canonical.com>
[axboe: add kerneldoc comment to skb, fold in skb leak fix]
Signed-off-by: NJens Axboe <axboe@kernel.dk>