io_uring drain_cqes_for never decrements io_uring_inflight_

[sgerbino]

Summary

drain_cqes_for advances CQEs without decrementing io_uring_inflight_, unlike
process_completions.

Detail

Unlike process_completions (which decrements at io_uring_scheduler.hpp:1115
and :1124), drain_cqes_for advances CQEs via io_uring_cq_advance without
decrementing the inflight counter — including for the cancel SQE it submits
itself (inflight_inc at :1262).

Acceptance criteria

• drain_cqes_for decrements io_uring_inflight_ for every CQE it advances,
  including the self-submitted cancel SQE.

References

io_uring_scheduler.hpp:1115, :1124, :1262.

Raised by Gennaro Prota (code-referenced). Author triage pending. Source: Boost
ML announcement.