Re: [PATCH v4 3/5] blockdev: unify qmp_blockdev_backup and blockdev-backup transaction paths

[Max Reitz <mreitz@redhat.com>]

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On 21.11.19 14:57, Sergio Lopez wrote:
> Issuing a blockdev-backup from qmp_blockdev_backup takes a slightly
> different path than when it's issued from a transaction. In the code,
> this is manifested as some redundancy between do_blockdev_backup() and
> blockdev_backup_prepare().
> 
> This change unifies both paths, merging do_blockdev_backup() and
> blockdev_backup_prepare(), and changing qmp_blockdev_backup() to
> create a transaction instead of calling do_backup_common() direcly.
> 
> As a side-effect, now qmp_blockdev_backup() is executed inside a
> drained section, as it happens when creating a blockdev-backup
> transaction. This change is visible from the user's perspective, as
> the job gets paused and immediately resumed before starting the actual
> work.
> 
> Signed-off-by: Sergio Lopez <slp@redhat.com>
> ---
>  blockdev.c | 60 ++++++++++++------------------------------------------
>  1 file changed, 13 insertions(+), 47 deletions(-)
> 
> diff --git a/blockdev.c b/blockdev.c
> index 5e85fc042e..152a0f7454 100644
> --- a/blockdev.c
> +++ b/blockdev.c

[...]

>  static void blockdev_backup_prepare(BlkActionState *common, Error **errp)
>  {
>      BlockdevBackupState *state = DO_UPCAST(BlockdevBackupState, common, common);
>      BlockdevBackup *backup;
> -    BlockDriverState *bs, *target;
> +    BlockDriverState *bs;
> +    BlockDriverState *target_bs;

The diff stat could have been a bit smaller by keeping this as it was,
but either way:

Reviewed-by: Max Reitz <mreitz@redhat.com>

>      AioContext *aio_context;
> -    Error *local_err = NULL;
>  
>      assert(common->action->type == TRANSACTION_ACTION_KIND_BLOCKDEV_BACKUP);
>      backup = common->action->u.blockdev_backup.data;
> @@ -1959,8 +1956,8 @@ static void blockdev_backup_prepare(BlkActionState *common, Error **errp)
>          return;
>      }
>  
> -    target = bdrv_lookup_bs(backup->target, backup->target, errp);
> -    if (!target) {
> +    target_bs = bdrv_lookup_bs(backup->target, backup->target, errp);
> +    if (!target_bs) {
>          return;
>      }
>  


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