Re: [DRAFT liburing] man: document new register/update API

[Jens Axboe <axboe@kernel.dk>]

On 8/28/21 1:18 PM, Pavel Begunkov wrote:
> Document
> - IORING_REGISTER_FILES2
> - IORING_REGISTER_FILES_UPDATE2,
> - IORING_REGISTER_BUFFERS2
> - IORING_REGISTER_BUFFERS_UPDATE,
> 
> And add a couple of words on registered resources (buffers, files)
> tagging.

Just a few comments below.

> @@ -95,6 +95,92 @@ wait for those to finish before proceeding.
>  An application need not unregister buffers explicitly before shutting
>  down the io_uring instance. Available since 5.1.
>  
> +.TP
> +.B IORING_REGISTER_BUFFERS2
> +Register buffers for I/O. similar to
> +.B IORING_REGISTER_BUFFERS
> +but aims to have a more extensible ABI.
> +
> +.I arg
> +points to a
> +.I struct io_uring_rsrc_register,
> +.I nr_args
> +should be set to the number of bytes in the structure.
> +
> +Field
> +.I data

I'd do:

The
.I data
field contains...

> +contains a pointer to a
> +.I struct iovec
> +array of
> +.I nr
> +entries.
> +.I tags
> +field should either be 0, then tagging is disabled, or point to an array

The
.I tags
field shoud be...

> +Note that resource updates, e.g.
> +.B IORING_REGISTER_BUFFERS_UPDATE,
> +don't necessarily deallocates resources by the time it returns, but they might

deallocate

> +be hold alive until all requests using it complete.

s/hold/held

> +
> +Available since 5.13.
> +
> +.PP
> +.in +8n
> +.EX
> +struct io_uring_rsrc_register {
> +    __u32 nr;
> +    __u32 resv;
> +    __u64 resv2;
> +    __aligned_u64 data;
> +    __aligned_u64 tags;
> +};

Move this up to where it's initially mentioned?

> @@ -138,6 +224,36 @@ Files are automatically unregistered when the io_uring instance is
>  torn down. An application need only unregister if it wishes to
>  register a new set of fds. Available since 5.1.
>  
> +.TP
> +.B IORING_REGISTER_FILES2
> +Register files for I/O. similar to
> +.B IORING_REGISTER_FILES.
> +
> +.I arg
> +points to a
> +.I struct io_uring_rsrc_register,
> +.I nr_args
> +should be set to the number of bytes in the structure.
> +
> +Field
> +.I data

The
.I data
field

> +contains a pointer to an array of
> +.I nr
> +file descriptors (signed 32 bit integers).
> +.I tags
> +field should either be 0 or or point to an array of
> +.I nr
> +"tags" (unsigned 64 bit integers). See
> +.B IORING_REGISTER_BUFFERS2
> +for more info on resource tagging.
> +
> +Note that resource updates, e.g.
> +.B IORING_REGISTER_FILES_UPDATE,
> +don't necessarily deallocates resources, but might hold it until all

deallocate

Just minor stuff, apart from that looks pretty good to me.

-- 
Jens Axboe