Re: [PATCH v2 09/36] block: return value from bdrv_replace_node()

[Kevin Wolf <kwolf@redhat.com>]

Am 27.11.2020 um 15:44 hat Vladimir Sementsov-Ogievskiy geschrieben:
> Functions with errp argument are not recommened to be void-functions.
> Improve bdrv_replace_node().
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  include/block/block.h |  4 ++--
>  block.c               | 14 ++++++++------
>  2 files changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/include/block/block.h b/include/block/block.h
> index 5d59984ad4..8f6100dad7 100644
> --- a/include/block/block.h
> +++ b/include/block/block.h
> @@ -346,8 +346,8 @@ int bdrv_create_file(const char *filename, QemuOpts *opts, Error **errp);
>  BlockDriverState *bdrv_new(void);
>  int bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top,
>                  Error **errp);
> -void bdrv_replace_node(BlockDriverState *from, BlockDriverState *to,
> -                       Error **errp);
> +int bdrv_replace_node(BlockDriverState *from, BlockDriverState *to,
> +                      Error **errp);
>  
>  int bdrv_parse_aio(const char *mode, int *flags);
>  int bdrv_parse_cache_mode(const char *mode, int *flags, bool *writethrough);
> diff --git a/block.c b/block.c
> index 3765c7caed..29082c6d47 100644
> --- a/block.c
> +++ b/block.c
> @@ -4537,14 +4537,14 @@ static bool should_update_child(BdrvChild *c, BlockDriverState *to)
>   * With auto_skip=false the error is returned if from has a parent which should
>   * not be updated.
>   */
> -static void bdrv_replace_node_common(BlockDriverState *from,
> -                                     BlockDriverState *to,
> -                                     bool auto_skip, Error **errp)
> +static int bdrv_replace_node_common(BlockDriverState *from,
> +                                    BlockDriverState *to,
> +                                    bool auto_skip, Error **errp)
>  {
> +    int ret = -EPERM;
>      BdrvChild *c, *next;
>      GSList *list = NULL, *p;
>      uint64_t perm = 0, shared = BLK_PERM_ALL;
> -    int ret;

I think I'd prefer setting ret in each error path. This makes it more
obvious that ret has the right value and hasn't been modified between
the initialisation and the error.

>  
>      /* Make sure that @from doesn't go away until we have successfully attached
>       * all of its parents to @to. */
> @@ -4600,10 +4600,12 @@ out:

Let's add an explicit ret = 0 right before the out: label.

>      g_slist_free(list);
>      bdrv_drained_end(from);
>      bdrv_unref(from);
> +
> +    return ret;
>  }

With these changes:

Reviewed-by: Kevin Wolf <kwolf@redhat.com>