Re: [RFC 0/8] io_uring: buffer registration enhancements

[Bijan Mottahedeh <bijan.mottahedeh@oracle.com>]

A gentle ping.

On 10/22/2020 4:13 PM, Bijan Mottahedeh wrote:
> Hi Jens,
> 
> This RFC implements a set of enhancements to buffer registration consistent
> with existing file registration functionality:
> 
> - buffer registration updates		IORING_REGISTER_BUFFERS_UPDATE
> 					IORING_OP_BUFFERS_UPDATE
> 
> - readv/writev with fixed buffers	IOSQE_FIXED_BUFFER
> 
> - buffer registration sharing		IORING_SETUP_SHARE_BUF
> 					IORING_SETUP_ATTACH_BUF
> 
> Patches 1,2 modularize existing buffer registration code.
> 
> Patch 3 generalizes fixed_file functionality to fixed_rsrc.
> 
> Patch 4 applies fixed_rsrc functionality for fixed buffers support.
> 
> Patch 5 generalizes files_update functionality to rsrc_update.
> 
> Patch 6 implements buffer registration update, and introduces
> IORING_REGISTER_BUFFERS_UPDATE and IORING_OP_BUFFERS_UPDATE, consistent
> with file registration update.
> 
> Patch 7 implements readv/writev support with fixed buffers, and introduces
> IOSQE_FIXED_BUFFER, consistent with fixed files.
> 
> Patch 8 implements buffer sharing among multiple rings; it works as
> follows based on previous conversations:
> 
> - A new ring, A,  is setup. Since no buffers have been registered, the
>    registered buffer state is an empty set, Z. That's different from the
>    NULL state in current implementation.
> 
> - Ring B is setup, attaching to Ring A. It's also attaching to it's
>    buffer registrations, now we have two references to the same empty
>    set, Z.
> 
> - Ring A registers buffers into set Z, which is no longer empty.
> 
> - Ring B sees this immediately, since it's already sharing that set.
> 
> TBD
> 
> - I think I have to add IORING_UNREGISTER_BUFFERS to
>    io_register_op_must_quiesce() but wanted to confirm.
> 
> - IORING_OP_SHUTDOWN has been removed but still in liburing, not sure why.
>    I wanted to verify before removing that functionality.
> 
> I have used liburing file-{register,update} tests as models for
> buffer-{register,update}, and it seems to work ok.
> 
> Bijan Mottahedeh (8):
>    io_uring: modularize io_sqe_buffer_register
>    io_uring: modularize io_sqe_buffers_register
>    io_uring: generalize fixed file functionality
>    io_uring: implement fixed buffers registration similar to fixed files
>    io_uring: generalize files_update functionlity to rsrc_update
>    io_uring: support buffer registration updates
>    io_uring: support readv/writev with fixed buffers
>    io_uring: support buffer registration sharing
> 
>   fs/io_uring.c                 | 1021 ++++++++++++++++++++++++++++++++---------
>   include/uapi/linux/io_uring.h |   15 +-
>   2 files changed, 807 insertions(+), 229 deletions(-)
>