Re: [Qemu-devel] [PATCH v2 4/6] raw-posix: Switch to bdrv_co_* interfaces

[Eric Blake <eblake@redhat.com>]

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On 06/14/2016 07:32 AM, Kevin Wolf wrote:
> In order to use the modern byte-based .bdrv_co_preadv/pwritev()
> interface, this patch switches raw-posix to coroutine-based interfaces
> as a first step. In terms of semantics and performance, it doesn't make
> a difference with the existing code whether we go from a coroutine to a
> callback-based interface already in block/io.c or only in linux-aio.c
> 
> As there have been concerns in the past that this change may be a step
> in the wrong direction with respect to a possible AIO fast path, the
> old callback-based interface for linux-aio is left around and can be
> reactivated when a fast path (e.g. directly from virtio-blk dataplane,
> bypassing the whole block layer) is implemented.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/linux-aio.c | 87 +++++++++++++++++++++++++++++++++++++++++--------------
>  block/raw-aio.h   |  4 +++
>  block/raw-posix.c | 59 +++++++++++++++++--------------------
>  3 files changed, 96 insertions(+), 54 deletions(-)

Reviewed-by: Eric Blake <eblake@redhat.com>


> @@ -1957,8 +1952,8 @@ BlockDriver bdrv_file = {
>      .bdrv_co_get_block_status = raw_co_get_block_status,
>      .bdrv_co_pwrite_zeroes = raw_co_pwrite_zeroes,
>  
> -    .bdrv_aio_readv = raw_aio_readv,
> -    .bdrv_aio_writev = raw_aio_writev,
> +    .bdrv_co_readv          = raw_co_readv,
> +    .bdrv_co_writev         = raw_co_writev,
>      .bdrv_aio_flush = raw_aio_flush,
>      .bdrv_aio_discard = raw_aio_discard,

The rest of this chunk doesn't try to align '='. Not worth a respin, but
something you may want to clean up on pull request.

>      .bdrv_refresh_limits = raw_refresh_limits,
> @@ -2405,8 +2400,8 @@ static BlockDriver bdrv_host_device = {
>      .create_opts         = &raw_create_opts,
>      .bdrv_co_pwrite_zeroes = hdev_co_pwrite_zeroes,
>  
> -    .bdrv_aio_readv	= raw_aio_readv,
> -    .bdrv_aio_writev	= raw_aio_writev,
> +    .bdrv_co_readv          = raw_co_readv,
> +    .bdrv_co_writev         = raw_co_writev,
>      .bdrv_aio_flush	= raw_aio_flush,
>      .bdrv_aio_discard   = hdev_aio_discard,
>      .bdrv_refresh_limits = raw_refresh_limits,

and this hunk is also inconsistent, but in a different way.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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