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>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20210428151804.439460-9-vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
8cad15b156