Re: [Qemu-devel] [PATCH v4 5/6] blockjob: refactor backup_start as backup_job_create

[Jeff Cody <jcody@redhat.com>]

On Tue, Nov 08, 2016 at 01:50:38AM -0500, John Snow wrote:
> Refactor backup_start as backup_job_create, which only creates the job,
> but does not automatically start it. The old interface, 'backup_start',
> is not kept in favor of limiting the number of nearly-identical interfaces
> that would have to be edited to keep up with QAPI changes in the future.
> 
> Callers that wish to synchronously start the backup_block_job can
> instead just call block_job_start immediately after calling
> backup_job_create.
> 
> Transactions are updated to use the new interface, calling block_job_start
> only during the .commit phase, which helps prevent race conditions where
> jobs may finish before we even finish building the transaction. This may
> happen, for instance, during empty block backup jobs.
> 
> Reported-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> Signed-off-by: John Snow <jsnow@redhat.com>
> ---
>  block/backup.c            | 26 ++++++++-------
>  block/replication.c       | 12 ++++---
>  blockdev.c                | 81 ++++++++++++++++++++++++++++++-----------------
>  include/block/block_int.h | 23 +++++++-------
>  4 files changed, 85 insertions(+), 57 deletions(-)

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