Re: [PATCH v6 0/5] io_uring: buffer registration enhancements

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

Gentle reminder to please review this next version.

> v6:
> 
> - address v5 comments
> - rebase on Pavel's rsrc generalization changes
> - see also TBD section below
> 
> v5:
> 
> - call io_get_fixed_rsrc_ref for buffers
> - make percpu_ref_release names consistent
> - rebase on for-5.12/io_uring
> - see also TBD section below
> 
> v4:
> 
> - address v3 comments (TBD REGISTER_BUFFERS)
> - rebase
> 
> 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
> 
> Patch 1 calls io_get_fixed_rsrc_ref() for buffers as well as files.
> 
> Patch 2 applies fixed_rsrc functionality for fixed buffers support.
> 
> Patch 3 generalize files_update functionality to rsrc_update.
> 
> Patch 4 implements buffer registration update, and introduces
> IORING_REGISTER_BUFFERS_UPDATE and IORING_OP_BUFFERS_UPDATE, consistent
> with file registration update.
> 
> Patch 5 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. Liburing test/self
> fails but seems unrelated to these changes.
> 
> TBD
> 
> - Need a patch from Pavel to address a race between fixed IO from async
> context and buffer unregister, or force buffer registration ops to do
> full quiesce.
> 
> Bijan Mottahedeh (5):
>    io_uring: call io_get_fixed_rsrc_ref for buffers
>    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 buffer registration sharing
> 
>   fs/io_uring.c                 | 448 +++++++++++++++++++++++++++++++++++++-----
>   include/uapi/linux/io_uring.h |   4 +
>   2 files changed, 403 insertions(+), 49 deletions(-)
>