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

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Fri, Feb 10, 2023 at 11:32:08PM +0800, Ming Lei wrote:
> 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!

I'm not familiar enough with the splice implementation to review these
patches, but the performance numbers you posted look great. This could
be very nice for ublk and FUSE servers!

Thanks,
Stefan

> 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
> 

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