Re: [PATCH v2 00/13] io_uring: buffer registration enhancements

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

On 07/12/2020 22:15, Bijan Mottahedeh wrote:
> v2:
> 
> - drop readv/writev with fixed buffers patch
> - handle ref_nodes both both files/buffers with a single ref_list
> - make file/buffer handling more unified
> 
> This patchset 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
> 
> - buffer registration sharing		IORING_SETUP_SHARE_BUF
> 					IORING_SETUP_ATTACH_BUF
> 
> I have kept the original patchset unchanged for the most part to
> facilitate reviewing and so this set adds a number of additional patches
> mostly making file/buffer handling more unified.

Thanks for the patches! I'd _really_ prefer for all s/files/rsrc/
renaming being in a single prep patch instead of spilling it all around.
I found one bug, but to be honest it's hard to get through when functional
changes and other cleanups are buried under tons of such renaming.

> 
> Patch 1-2 modularize existing buffer registration code.
> 
> Patch 3-7 generalize fixed_file functionality to fixed_rsrc.
> 
> Patch 8 applies fixed_rsrc functionality for fixed buffers support.
> 
> Patch 9-10 generalize files_update functionality to rsrc_update.
> 
> Patch 11 implements buffer registration update, and introduces
> IORING_REGISTER_BUFFERS_UPDATE and IORING_OP_BUFFERS_UPDATE, consistent
> with file registration update.
> 
> Patch 12 generalizes fixed resource allocation 
> 
> Patch 13 implements buffer sharing among multiple rings; it works as follows:
> 
> - 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.
> 
> Testing
> 
> I have used liburing file-{register,update} tests as models for
> buffer-{register,update,share}, tests and they run ok.
> 
> TBD
> 
> - Haven't addressed Pavel's comment yet on using a single opcode for
> files/buffers update, pending Jen's opinion.  Could we encode the resource
> type into the sqe (e.g. rw_flags)?
> 
> Bijan Mottahedeh (13):
>   io_uring: modularize io_sqe_buffer_register
>   io_uring: modularize io_sqe_buffers_register
>   io_uring: generalize fixed file functionality
>   io_uring: rename fixed_file variables to fixed_rsrc
>   io_uring: separate ref_list from fixed_rsrc_data
>   io_uring: generalize fixed_file_ref_node functionality
>   io_uring: add rsrc_ref locking routines
>   io_uring: implement fixed buffers registration similar to fixed files
>   io_uring: create common fixed_rsrc_ref_node handling routines
>   io_uring: generalize files_update functionlity to rsrc_update
>   io_uring: support buffer registration updates
>   io_uring: create common fixed_rsrc_data allocation routines.
>   io_uring: support buffer registration sharing
> 
>  fs/io_uring.c                 | 1004 +++++++++++++++++++++++++++++------------
>  include/uapi/linux/io_uring.h |   12 +-
>  2 files changed, 732 insertions(+), 284 deletions(-)
> 

-- 
Pavel Begunkov