Re: [PATCH for-5.0 v2 11/23] block: Use bdrv_recurse_can_replace()

[Kevin Wolf]

Am 11.11.2019 um 17:02 hat Max Reitz geschrieben:
> Let check_to_replace_node() use the more specialized
> bdrv_recurse_can_replace() instead of
> bdrv_recurse_is_first_non_filter(), which is too restrictive.
> 
> Signed-off-by: Max Reitz <address@hidden>
> ---
>  block.c | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/block.c b/block.c
> index de53addeb0..7608f21570 100644
> --- a/block.c
> +++ b/block.c
> @@ -6243,6 +6243,17 @@ bool bdrv_recurse_can_replace(BlockDriverState *bs,
>      return false;
>  }
>  
> +/*
> + * Check whether the given @node_name can be replaced by a node that
> + * has the same data as @parent_bs.  If so, return @node_name's BDS;
> + * NULL otherwise.
> + *
> + * @node_name must be a (recursive) *child of @parent_bs (or this
> + * function will return NULL).
> + *
> + * The result (whether the node can be replaced or not) is only valid
> + * for as long as no graph changes occur.
> + */
>  BlockDriverState *check_to_replace_node(BlockDriverState *parent_bs,
>                                          const char *node_name, Error **errp)
>  {
> @@ -6267,8 +6278,11 @@ BlockDriverState 
> *check_to_replace_node(BlockDriverState *parent_bs,
>       * Another benefit is that this tests exclude backing files which are
>       * blocked by the backing blockers.
>       */
> -    if (!bdrv_recurse_is_first_non_filter(parent_bs, to_replace_bs)) {
> -        error_setg(errp, "Only top most non filter can be replaced");
> +    if (!bdrv_recurse_can_replace(parent_bs, to_replace_bs)) {
> +        error_setg(errp, "Cannot replace '%s' by a node mirrored from '%s', "
> +                   "because it cannot be guaranteed that doing so would not "
> +                   "lead to an abrupt change of visible data",
> +                   node_name, parent_bs->node_name);

If this function is only supposed to be used in the context of the
mirror job, moving it into block/mirror.c could be considered as a
cleanup on top.

Kevin