Re: [PATCH v3 08/36] util: add transactions.c

[Kevin Wolf]

Am 17.03.2021 um 15:35 hat Vladimir Sementsov-Ogievskiy geschrieben:
> Add simple transaction API to use in further update of block graph
> operations.
> 
> Supposed usage is:
> 
> - "prepare" is main function of the action and it should make the main
>   effect of the action to be visible for the following actions, keeping
>   possibility of roll-back, saving necessary things in action state,
>   which is prepended to the action list (to do that, prepare func
>   should call tran_add()). So, driver struct doesn't include "prepare"
>   field, as it is supposed to be called directly.
> 
> - commit/rollback is supposed to be called for the list of action
>   states, to commit/rollback all the actions in reverse order
> 
> - When possible "commit" should not make visible effect for other
>   actions, which make possible transparent logical interaction between
>   actions.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  include/qemu/transactions.h | 63 ++++++++++++++++++++++++
>  util/transactions.c         | 96 +++++++++++++++++++++++++++++++++++++
>  MAINTAINERS                 |  6 +++
>  util/meson.build            |  1 +
>  4 files changed, 166 insertions(+)
>  create mode 100644 include/qemu/transactions.h
>  create mode 100644 util/transactions.c
> 
> diff --git a/include/qemu/transactions.h b/include/qemu/transactions.h
> new file mode 100644
> index 0000000000..e7add9637f
> --- /dev/null
> +++ b/include/qemu/transactions.h
> @@ -0,0 +1,63 @@
> +/*
> + * Simple transactions API
> + *
> + * Copyright (c) 2021 Virtuozzo International GmbH.
> + *
> + * Author:
> + *  Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program. If not, see <http://www.gnu.org/licenses/>.
> + *
> + *
> + * = Generic transaction API =
> + *
> + * The intended usage is the following: you create "prepare" functions, which
> + * represents the actions. They will usually have Transaction* argument, and
> + * call tran_add() to register finalization callbacks. For finalization
> + * callbacks, prepare corresponding TransactionActionDrv structures.
> + *
> + * Than, when you need to make a transaction, create an empty Transaction by

Then

> + * tran_create(), call your "prepare" functions on it, and finally call
> + * tran_abort() or tran_commit() to finalize the transaction by corresponding
> + * finalization actions in reverse order.
> + */
> +
> +#ifndef QEMU_TRANSACTIONS_H
> +#define QEMU_TRANSACTIONS_H
> +
> +#include <gmodule.h>
> +
> +typedef struct TransactionActionDrv {
> +    void (*abort)(void *opaque);
> +    void (*commit)(void *opaque);
> +    void (*clean)(void *opaque);
> +} TransactionActionDrv;
> +
> +typedef struct Transaction Transaction;
> +
> +Transaction *tran_new(void);
> +void tran_add(Transaction *tran, TransactionActionDrv *drv, void *opaque);
> +void tran_abort(Transaction *tran);
> +void tran_commit(Transaction *tran);
> +
> +static inline void tran_finalize(Transaction *tran, int ret)
> +{
> +    if (ret < 0) {
> +        tran_abort(tran);
> +    } else {
> +        tran_commit(tran);
> +    }
> +}
> +
> +#endif /* QEMU_TRANSACTIONS_H */
> diff --git a/util/transactions.c b/util/transactions.c
> new file mode 100644
> index 0000000000..d0bc9a3e73
> --- /dev/null
> +++ b/util/transactions.c
> @@ -0,0 +1,96 @@
> +/*
> + * Simple transactions API
> + *
> + * Copyright (c) 2021 Virtuozzo International GmbH.
> + *
> + * Author:
> + *  Sementsov-Ogievskiy Vladimir <vsementsov@virtuozzo.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program. If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include "qemu/osdep.h"
> +
> +#include "qemu/transactions.h"
> +#include "qemu/queue.h"
> +
> +typedef struct TransactionAction {
> +    TransactionActionDrv *drv;
> +    void *opaque;
> +    QSLIST_ENTRY(TransactionAction) entry;

"next" is a bit more conventional as a name, but by far not as much as I
thought, so no objection.

With the than/then typo fixed:
Reviewed-by: Kevin Wolf <kwolf@redhat.com>