[PATCH v2 0/4] allow to skip CQE posting

[Pavel Begunkov <asml.silence@gmail.com>]

It's expensive enough to post an CQE, and there are other
reasons to want to ignore them, e.g. for link handling and
it may just be more convenient for the userspace.

Try to cover most of the use cases with one flag. The overhead
is one "if (cqe->flags & IOSQE_CQE_SKIP_SUCCESS)" check per
requests and a bit bloated req_set_fail(), should be bearable.

See 2/4 for the actual description of the flag.

v2: don't allow drain with the new flag (see 4/4)
    add IORING_FEAT_CQE_SKIP

Pavel Begunkov (4):
  io_uring: clean cqe filling functions
  io_uring: add option to skip CQE posting
  io_uring: don't spinlock when not posting CQEs
  io_uring: disable drain with cqe skip

 fs/io_uring.c                 | 114 +++++++++++++++++++++++-----------
 include/uapi/linux/io_uring.h |   4 ++
 2 files changed, 81 insertions(+), 37 deletions(-)

-- 
2.33.1