Re: [PATCH v2 04/11] bdrv_child_try_change_aio_context: add transaction parameter

[Kevin Wolf <kwolf@redhat.com>]

Am 25.07.2022 um 14:21 hat Emanuele Giuseppe Esposito geschrieben:
> This enables the caller to use the same transaction to also
> keep track of aiocontext changes.
> 
> Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>

What you're really doing here is factoring out the recursive phase.
However, the factored out function is never used from anywhere else,
so I don't understand the purpose of this patch. It feels like an
unnecessary complication of the code.

The commit message is unclear to me, too: Who is the caller of
bdrv_child_try_change_aio_context() that it mentions, and why does it
make a difference to it how the code is organised internally?

Is this some artifact of changes you made and we don't need it any more
now?

>  block.c                            | 31 ++++++++++++++++++++++++------
>  include/block/block-global-state.h |  5 +++++
>  2 files changed, 30 insertions(+), 6 deletions(-)
> 
> diff --git a/block.c b/block.c
> index c02a628336..221bf90268 100644
> --- a/block.c
> +++ b/block.c
> @@ -7643,17 +7643,16 @@ int bdrv_child_try_set_aio_context(BlockDriverState *bs, AioContext *ctx,
>   * For the same reason, it temporarily holds also the new AioContext, since
>   * bdrv_drained_end calls BDRV_POLL_WHILE that assumes the lock is taken too.
>   */
> -int bdrv_child_try_change_aio_context(BlockDriverState *bs, AioContext *ctx,
> -                                      BdrvChild *ignore_child, Error **errp)
> +int bdrv_child_try_change_aio_context_tran(BlockDriverState *bs,
> +                                           AioContext *ctx,
> +                                           BdrvChild *ignore_child,
> +                                           Transaction *tran,
> +                                           Error **errp)

As mentioned above, this is never used anywhere else than from
bdrv_child_try_change_aio_context(), so if we want to keep the patch, it
should be static at least.

Maybe find a better name, too, because all of the transaction related
operations are in the caller.

The function comment is not accurate any more either because it
described the whole of bdrv_child_try_change_aio_context(), while this
function only contains the recursive part.

Kevin