Re: [Qemu-devel] [Qemu-block] [PATCH v5 06/12] block: Add "drained begin/end" for transactional external snapshot

[Jeff Cody <jcody@redhat.com>]

On Wed, Oct 21, 2015 at 10:06:43AM +0800, Fam Zheng wrote:
> This ensures the atomicity of the transaction by avoiding processing of
> external requests such as those from ioeventfd.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  blockdev.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/blockdev.c b/blockdev.c
> index 35e5719..e4a5eb4 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -1569,6 +1569,7 @@ static void external_snapshot_prepare(BlkTransactionState *common,
>      /* Acquire AioContext now so any threads operating on old_bs stop */
>      state->aio_context = bdrv_get_aio_context(state->old_bs);
>      aio_context_acquire(state->aio_context);
> +    bdrv_drained_begin(state->old_bs);
>  
>      if (!bdrv_is_inserted(state->old_bs)) {
>          error_setg(errp, QERR_DEVICE_HAS_NO_MEDIUM, device);
> @@ -1638,8 +1639,6 @@ static void external_snapshot_commit(BlkTransactionState *common)
>       * don't want to abort all of them if one of them fails the reopen */
>      bdrv_reopen(state->old_bs, state->old_bs->open_flags & ~BDRV_O_RDWR,
>                  NULL);
> -
> -    aio_context_release(state->aio_context);
>  }
>  
>  static void external_snapshot_abort(BlkTransactionState *common)
> @@ -1649,7 +1648,14 @@ static void external_snapshot_abort(BlkTransactionState *common)
>      if (state->new_bs) {
>          bdrv_unref(state->new_bs);
>      }
> +}
> +
> +static void external_snapshot_clean(BlkTransactionState *common)
> +{
> +    ExternalSnapshotState *state =
> +                             DO_UPCAST(ExternalSnapshotState, common, common);
>      if (state->aio_context) {
> +        bdrv_drained_end(state->old_bs);
>          aio_context_release(state->aio_context);
>      }
>  }
> @@ -1809,6 +1815,7 @@ static const BdrvActionOps actions[] = {
>          .prepare  = external_snapshot_prepare,
>          .commit   = external_snapshot_commit,
>          .abort = external_snapshot_abort,
> +        .clean = external_snapshot_clean,
>      },
>      [TRANSACTION_ACTION_KIND_DRIVE_BACKUP] = {
>          .instance_size = sizeof(DriveBackupState),
> -- 
> 2.4.3
> 
> 

Reviewed-by: Jeff Cody <jcody@redhat.com>