Re: [Qemu-devel] [Qemu-block] [PATCH v5 07/12] block: Add "drained begin/end" for transactional backup

[Jeff Cody <jcody@redhat.com>]

On Wed, Oct 21, 2015 at 10:06:44AM +0800, Fam Zheng wrote:
> This ensures the atomicity of the transaction by avoiding processing of
> external requests such as those from ioeventfd.
> 
> Move the assignment to state->bs up right after bdrv_drained_begin, so
> that we can use it in the clean callback. The abort callback will still
> check bs->job and state->job, so it's OK.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  blockdev.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/blockdev.c b/blockdev.c
> index e4a5eb4..0a7848b 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -1684,9 +1684,16 @@ static void drive_backup_prepare(BlkTransactionState *common, Error **errp)
>          return;
>      }
>  
> +    if (!blk_is_available(blk)) {
> +        error_setg(errp, QERR_DEVICE_HAS_NO_MEDIUM, backup->device);
> +        return;
> +    }
> +
>      /* AioContext is released in .clean() */
>      state->aio_context = blk_get_aio_context(blk);
>      aio_context_acquire(state->aio_context);
> +    bdrv_drained_begin(blk_bs(blk));
> +    state->bs = blk_bs(blk);
>  
>      qmp_drive_backup(backup->device, backup->target,
>                       backup->has_format, backup->format,
> @@ -1702,7 +1709,6 @@ static void drive_backup_prepare(BlkTransactionState *common, Error **errp)
>          return;
>      }
>  
> -    state->bs = blk_bs(blk);
>      state->job = state->bs->job;
>  }
>  
> @@ -1722,6 +1728,7 @@ static void drive_backup_clean(BlkTransactionState *common)
>      DriveBackupState *state = DO_UPCAST(DriveBackupState, common, common);
>  
>      if (state->aio_context) {
> +        bdrv_drained_end(state->bs);
>          aio_context_release(state->aio_context);
>      }
>  }
> -- 
> 2.4.3
> 
> 

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