Originally the transaction QMP command was just for taking snapshots. The command became more general when drive-backup and abort were added.
It is more accurate to say the command is about performing operations on an atomic group than to say it is about snapshots. Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com> --- blockdev.c | 16 ++++++---------- 1 file changed, 6 insertions(+), 10 deletions(-) diff --git a/blockdev.c b/blockdev.c index 57910b8..778509b 100644 --- a/blockdev.c +++ b/blockdev.c @@ -1159,7 +1159,7 @@ SnapshotInfo *qmp_blockdev_snapshot_delete_internal_sync(const char *device, return info; } -/* New and old BlockDriverState structs for group snapshots */ +/* New and old BlockDriverState structs for atomic group operations */ typedef struct BlkTransactionState BlkTransactionState; @@ -1530,9 +1530,8 @@ static const BdrvActionOps actions[] = { }; /* - * 'Atomic' group snapshots. The snapshots are taken as a set, and if any fail - * then we do not pivot any of the devices in the group, and abandon the - * snapshots + * 'Atomic' group operations. The operations are performed as a set, and if + * any fail then we roll back all operations in the group. */ void qmp_transaction(TransactionActionList *dev_list, Error **errp) { @@ -1543,10 +1542,10 @@ void qmp_transaction(TransactionActionList *dev_list, Error **errp) QSIMPLEQ_HEAD(snap_bdrv_states, BlkTransactionState) snap_bdrv_states; QSIMPLEQ_INIT(&snap_bdrv_states); - /* drain all i/o before any snapshots */ + /* drain all i/o before any operations */ bdrv_drain_all(); - /* We don't do anything in this loop that commits us to the snapshot */ + /* We don't do anything in this loop that commits us to the operations */ while (NULL != dev_entry) { TransactionAction *dev_info = NULL; const BdrvActionOps *ops; @@ -1581,10 +1580,7 @@ void qmp_transaction(TransactionActionList *dev_list, Error **errp) goto exit; delete_and_fail: - /* - * failure, and it is all-or-none; abandon each new bs, and keep using - * the original bs for all images - */ + /* failure, and it is all-or-none; roll back all operations */ QSIMPLEQ_FOREACH(state, &snap_bdrv_states, entry) { if (state->ops->abort) { state->ops->abort(state); -- 2.1.0