Re: [PATCH v3 5/6] block/linux-aio: convert to blk_io_plug_call() API

[Stefano Garzarella <sgarzare@xxxxxxxxxx>]

On Tue, May 30, 2023 at 02:09:58PM -0400, Stefan Hajnoczi wrote:
> Stop using the .bdrv_co_io_plug() API because it is not multi-queue
> block layer friendly. Use the new blk_io_plug_call() API to batch I/O
> submission instead.
>
> Note that a dev_max_batch check is dropped in laio_io_unplug() because
> the semantics of unplug_fn() are different from .bdrv_co_unplug():
> 1. unplug_fn() is only called when the last blk_io_unplug() call occurs,
>   not every time blk_io_unplug() is called.
> 2. unplug_fn() is per-thread, not per-BlockDriverState, so there is no
>   way to get per-BlockDriverState fields like dev_max_batch.
>
> Therefore this condition cannot be moved to laio_unplug_fn(). It is not
> obvious that this condition affects performance in practice, so I am
> removing it instead of trying to come up with a more complex mechanism
> to preserve the condition.
>
> Signed-off-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
> Reviewed-by: Eric Blake <eblake@xxxxxxxxxx>
> ---
> include/block/raw-aio.h |  7 -------
> block/file-posix.c      | 28 ----------------------------
> block/linux-aio.c       | 41 +++++++++++------------------------------
> 3 files changed, 11 insertions(+), 65 deletions(-)
LGTM!

Reviewed-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>