Re: [PATCH v3 00/13] io_uring: buffer registration enhancements

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

A reminder to please review this version.

> v3:
> 
> - batch file->rsrc renames into a signle patch when possible
> - fix other review changes from v2
> - fix checkpatch warnings
> 
> 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.
> 
> 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
> 
> - I tried to use a single opcode for files/buffers but ran into an
> issue since work_flags is different for files/buffers.  This should
> be ok for the most part since req->work.flags is ultimately examined;
> however, there are place where io_op_defs[opcode].work_flags is examined
> directly, and I wasn't sure what would the best way to handle that.
> 
> - Need to still address Pavel's comments about deadlocks. I figure
> to send out the set anyway since this is a last patch and may even be
> handled separately.
> 
> Bijan Mottahedeh (13):
>    io_uring: modularize io_sqe_buffer_register
>    io_uring: modularize io_sqe_buffers_register
>    io_uring: rename file related variables to rsrc
>    io_uring: generalize io_queue_rsrc_removal
>    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, 735 insertions(+), 281 deletions(-)
>