[PATCH 0/4] io_uring: add IORING_OP_READ[WRITE]_SPLICE_BUF

[Ming Lei <ming.lei@redhat.com>]

Hello,

Add two OPs which buffer is retrieved via kernel splice for supporting
fuse/ublk zero copy.

The 1st patch enhances direct pipe & splice for moving pages in kernel,
so that the two added OPs won't be misused, and avoid potential security
hole.

The 2nd patch allows splice_direct_to_actor() caller to ignore signal
if the actor won't block and can be done in bound time.

The 3rd patch add the two OPs.

The 4th patch implements ublk's ->splice_read() for supporting
zero copy.

ublksrv(userspace):

https://github.com/ming1/ubdsrv/commits/io_uring_splice_buf
    
So far, only loop/null target implements zero copy in above branch:
    
	ublk add -t loop -f $file -z
	ublk add -t none -z

Basic FS/IO function is verified, mount/kernel building & fio
works fine, and big chunk IO(BS: 64k/512k) performance gets improved
obviously.
 
Any comment is welcome!

Ming Lei (4):
  fs/splice: enhance direct pipe & splice for moving pages in kernel
  fs/splice: allow to ignore signal in __splice_from_pipe
  io_uring: add IORING_OP_READ[WRITE]_SPLICE_BUF
  ublk_drv: support splice based read/write zero copy

 drivers/block/ublk_drv.c      | 169 +++++++++++++++++++++++++++++++--
 fs/splice.c                   |  19 +++-
 include/linux/pipe_fs_i.h     |  10 ++
 include/linux/splice.h        |  23 +++++
 include/uapi/linux/io_uring.h |   2 +
 include/uapi/linux/ublk_cmd.h |  31 +++++-
 io_uring/opdef.c              |  37 ++++++++
 io_uring/rw.c                 | 174 +++++++++++++++++++++++++++++++++-
 io_uring/rw.h                 |   1 +
 9 files changed, 456 insertions(+), 10 deletions(-)

-- 
2.31.1