[PATCH v2 0/5] io_uring: avoid uring_lock for IORING_SETUP_SINGLE_ISSUER

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

As far as I can tell, setting IORING_SETUP_SINGLE_ISSUER when creating
an io_uring doesn't actually enable any additional optimizations (aside
from being a requirement for IORING_SETUP_DEFER_TASKRUN). This series
leverages IORING_SETUP_SINGLE_ISSUER's guarantee that only one task
submits SQEs to skip taking the uring_lock mutex in the submission and
task work paths.

First, we need to close a hole in the IORING_SETUP_SINGLE_ISSUER checks
where IORING_REGISTER_CLONE_BUFFERS only checks whether the thread is
allowed to access one of the two io_urings. It assumes the uring_lock
will prevent concurrent access to the other io_uring, but this will no
longer be the case after the optimization to skip taking uring_lock.

We also need to remove the unused filetable.h #include from io_uring.h
to avoid an #include cycle.

v2:
- Don't enable these optimizations for IORING_SETUP_SQPOLL, as we still
  need to synchronize SQ thread submission with io_uring_register()

Caleb Sander Mateos (5):
  io_uring: don't include filetable.h in io_uring.h
  io_uring/rsrc: respect submitter_task in io_register_clone_buffers()
  io_uring: clear IORING_SETUP_SINGLE_ISSUER for IORING_SETUP_SQPOLL
  io_uring: factor out uring_lock helpers
  io_uring: avoid uring_lock for IORING_SETUP_SINGLE_ISSUER

 io_uring/cancel.c    |  1 +
 io_uring/fdinfo.c    |  2 +-
 io_uring/filetable.c |  3 +-
 io_uring/io_uring.c  | 67 +++++++++++++++++++++++++++++---------------
 io_uring/io_uring.h  | 43 ++++++++++++++++++++++------
 io_uring/kbuf.c      |  6 ++--
 io_uring/net.c       |  1 +
 io_uring/notif.c     |  5 ++--
 io_uring/notif.h     |  3 +-
 io_uring/openclose.c |  1 +
 io_uring/poll.c      |  2 +-
 io_uring/register.c  |  1 +
 io_uring/rsrc.c      | 10 ++++++-
 io_uring/rsrc.h      |  3 +-
 io_uring/rw.c        |  3 +-
 io_uring/splice.c    |  1 +
 io_uring/waitid.c    |  2 +-
 17 files changed, 111 insertions(+), 43 deletions(-)

-- 
2.45.2