linux-kernel - [PATCH 0/4] io_uring: avoid uring_lock for IORING_SETUP_SINGLE

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Message-ID: <20250903032656.2012337-1-csander@purestorage.com>
Date: Tue,  2 Sep 2025 21:26:52 -0600
From: Caleb Sander Mateos <csander@...estorage.com>
To: Jens Axboe <axboe@...nel.dk>
Cc: io-uring@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Caleb Sander Mateos <csander@...estorage.com>
Subject: [PATCH 0/4] io_uring: avoid uring_lock for IORING_SETUP_SINGLE_ISSUER

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.

Caleb Sander Mateos (4):
  io_uring: don't include filetable.h in io_uring.h
  io_uring/rsrc: respect submitter_task in io_register_clone_buffers()
  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  | 58 +++++++++++++++++++++++++++-----------------
 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, 102 insertions(+), 43 deletions(-)

-- 
2.45.2