Re: [Qemu-devel] [PATCH v5 10/14] blockdev: make BlockJobTxn available to qmp 'transaction'

[Max Reitz <mreitz@redhat.com>]

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On 07.09.2015 09:34, Fam Zheng wrote:
> From: Stefan Hajnoczi <stefanha@redhat.com>
> 
> Provide a BlockJobTxn to actions executed in a qmp 'transaction'
> command.  This allows actions to make their block jobs either complete
> as a group or fail/cancel together.
> 
> The next patch adds the first user.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> Reviewed-by: Fam Zheng <famz@redhat.com>
> Reviewed-by: John Snow <jsnow@redhat.com>

You can vouch for yourself, but can you vouch for John being fine with
the change from v4? ;-)

> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  blockdev.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/blockdev.c b/blockdev.c
> index 4ebded8..3d5e5cd 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -1285,6 +1285,7 @@ typedef struct BlkActionOps {
>  struct BlkActionState {
>      TransactionAction *action;
>      const BlkActionOps *ops;
> +    BlockJobTxn *block_job_txn;
>      QSIMPLEQ_ENTRY(BlkActionState) entry;
>  };
>  
> @@ -1889,12 +1890,15 @@ static const BlkActionOps actions[] = {
>  void qmp_transaction(TransactionActionList *dev_list, Error **errp)
>  {
>      TransactionActionList *dev_entry = dev_list;
> +    BlockJobTxn *block_job_txn;
>      BlkActionState *state, *next;
>      Error *local_err = NULL;
>  
>      QSIMPLEQ_HEAD(snap_bdrv_states, BlkActionState) snap_bdrv_states;
>      QSIMPLEQ_INIT(&snap_bdrv_states);
>  
> +    block_job_txn = block_job_txn_new();
> +
>      /* drain all i/o before any operations */
>      bdrv_drain_all();
>  
> @@ -1914,6 +1918,7 @@ void qmp_transaction(TransactionActionList *dev_list, Error **errp)
>          state = g_malloc0(ops->instance_size);
>          state->ops = ops;
>          state->action = dev_info;
> +        state->block_job_txn = block_job_txn;
>          QSIMPLEQ_INSERT_TAIL(&snap_bdrv_states, state, entry);
>  
>          state->ops->prepare(state, &local_err);
> @@ -1940,6 +1945,7 @@ delete_and_fail:
>          }
>      }
>  exit:
> +    block_job_txn_unref(block_job_txn);
>      QSIMPLEQ_FOREACH_SAFE(state, &snap_bdrv_states, entry, next) {
>          if (state->ops->clean) {
>              state->ops->clean(state);
> 

I'd put the unref() call after the FOREACH loop, since the txn is
referenced by every state->block_job_txn, so the state->ops->clean()
operation may still try to access that field.

Max


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