[PATCH v5 0/5] io_uring/uring_cmd: allow non-iopoll cmds with IORING_SETUP_IOPOLL

[Caleb Sander Mateos <csander@purestorage.com>]

Currently, creating an io_uring with IORING_SETUP_IOPOLL requires all
requests issued to it to support iopoll. This prevents, for example,
using ublk zero-copy together with IORING_SETUP_IOPOLL, as ublk
zero-copy buffer registrations are performed using a uring_cmd. There's
no technical reason why these non-iopoll uring_cmds can't be supported.
They will either complete synchronously or via an external mechanism
that calls io_uring_cmd_done(), io_uring_cmd_post_mshot_cqe32(), or
io_uring_mshot_cmd_post_cqe(), so they don't need to be polled.

Allow uring_cmd requests to be issued to IORING_SETUP_IOPOLL io_urings
even if their files don't implement ->uring_cmd_iopoll().

Use a new REQ_F_IOPOLL flag to track whether a request is using iopoll.
This makes the iopoll_queue opcode definition flag unnecessary.

The last commit removes an unnecessary IO_URING_F_IOPOLL check in
nvme_dev_uring_cmd() as NVMe admin passthru commands can be issued to
IORING_SETUP_IOPOLL io_urings now.

v5: perform one iteration of iopoll when min_events == 0 (Claude)

v4: check non-iopoll CQEs against min_events in io_iopoll_check() (Ming)

v3: fix REW -> REQ typo (Anuj)

v2:
- Add REQ_F_IOPOLL request flag, remove redundant iopoll_queue
- Split IORING_OP_URING_CMD128 fix to a separate commit

Caleb Sander Mateos (5):
  io_uring: add REQ_F_IOPOLL
  io_uring: remove iopoll_queue from struct io_issue_def
  io_uring: count CQEs in io_iopoll_check()
  io_uring/uring_cmd: allow non-iopoll cmds with IORING_SETUP_IOPOLL
  nvme: remove nvme_dev_uring_cmd() IO_URING_F_IOPOLL check

 drivers/nvme/host/ioctl.c      |  4 ----
 include/linux/io_uring_types.h |  3 +++
 io_uring/io_uring.c            | 19 ++++++-------------
 io_uring/opdef.c               | 10 ----------
 io_uring/opdef.h               |  2 --
 io_uring/rw.c                  | 11 ++++++-----
 io_uring/uring_cmd.c           |  9 ++++-----
 7 files changed, 19 insertions(+), 39 deletions(-)

-- 
2.45.2