Re: [PATCH v8 1/5] QIOChannel: Add flags on io_writev and introduce io_flush callback

[Peter Xu]

On Tue, Feb 01, 2022 at 03:28:59AM -0300, Leonardo Bras wrote:
> Add flags to io_writev and introduce io_flush as optional callback to
> QIOChannelClass, allowing the implementation of zero copy writes by
> subclasses.
> 
> How to use them:
> - Write data using qio_channel_writev*(...,QIO_CHANNEL_WRITE_FLAG_ZERO_COPY),
> - Wait write completion with qio_channel_flush().
> 
> Notes:
> As some zero copy write implementations work asynchronously, it's
> recommended to keep the write buffer untouched until the return of
> qio_channel_flush(), to avoid the risk of sending an updated buffer
> instead of the buffer state during write.
> 
> As io_flush callback is optional, if a subclass does not implement it, then:
> - io_flush will return 0 without changing anything.
> 
> Also, some functions like qio_channel_writev_full_all() were adapted to
> receive a flag parameter. That allows shared code between zero copy and
> non-zero copy writev, and also an easier implementation on new flags.
> 
> Signed-off-by: Leonardo Bras <leobras@redhat.com>

With Dan's comment addressed on removing the redundant assertion:

Reviewed-by: Peter Xu <peterx@redhat.com>

-- 
Peter Xu