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

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

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

- 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(-)

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1.8.3.1