Re: [PATCH v1 proxmox-backup 1/3] api: backup: don't verify total file size for incremental backups

[Christian Ebner <c.ebner@proxmox.com>]

On 3/10/26 5:09 PM, Robert Obkircher wrote:
> This fixes incremental qemu backups, where the submitted value is the
> upload size instead of the total size.

Should we fix the `size` in the close_image() call on 
proxmox-backup-qemu as well? This is documented as the file size, not 
the upload size after all. Didn't look into it to deep, but 
`info.device_size` should be the correct value there. This can be a 
followup though and should not block/delay this crucial bugfix.

> 
> Avoiding the check is preferable over breaking backwards compatability
> of the API because it was only relevant for detecting potential bugs.
> 

It is best practice to blame the commit introducing the issue for reference:

Fixes: 760f40de ("api: verify fixed index writer size on close")

> Signed-off-by: Robert Obkircher <r.obkircher@proxmox.com>
> ---
>   src/api2/backup/environment.rs | 14 +++++++-------
>   1 file changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/src/api2/backup/environment.rs b/src/api2/backup/environment.rs
> index 657daa41..ab623f1f 100644
> --- a/src/api2/backup/environment.rs
> +++ b/src/api2/backup/environment.rs
> @@ -632,14 +632,14 @@ impl BackupEnvironment {
>                       );
>                   }
>               }
> -        }
>   
> -        let writer_size = data.index.size();
> -        if size != writer_size {
> -            bail!(
> -                "fixed writer '{}' close failed - unexpected size ({size} != {writer_size})",
> -                data.name,
> -            );
> +            let writer_size = data.index.size();
> +            if size != writer_size {
> +                bail!(
> +                    "fixed writer '{}' close failed - unexpected size ({size} != {writer_size})",
> +                    data.name,
> +                );
> +            }
>           }
>   
>           let expected_csum = data.index.close()?;