Re: [Qemu-devel] [PATCH 2/6] change vectored block I/O API to plain iovecs

[Avi Kivity]

Christoph Hellwig wrote:
> QEMUIOVector is a useful helper for the dma-helper.c internals but for a generic
> block API it's more of hindrance.  Some top-level consumers like virtio-blk
> already have the plain iovec and segment number at hand and can pass it down
> directly, and for those that just have a single element and need to fake up
> a vector the plain iovec also is a lot easier.
>   

virtio gets its iovecs through a hacky (and incorrect, try >=4G) 
method.  IMO virtio should be fixed to use the dma api, at which point 
it will start to use QEMUIOVector anyway,

> Last but not leas we want to push down vectored I/O to the lowest level,
> and if posix-aio-compat.c wants to stay somewhat true to it's goal of
> beeing like an ehanced posix AIO API it should stick to posix types.
>   

Internally yes, but why should bdrv_* not use QEMUIOVector?  That API 
isn't very interested in posix.

>  static BlockDriverAIOCB *bdrv_aio_rw_vector(BlockDriverState *bs,
>                                              int64_t sector_num,
> -                                            QEMUIOVector *iov,
> +                                            struct iovec *iov,
> +                                           int nr_iov,
>                                              int nb_sectors,
>                                              BlockDriverCompletionFunc *cb,
>                                              void *opaque,
>   

Note qemu never uses tabs in source code.

--
error compiling committee.c: too many arguments to function