Re: [PATCH v1 proxmox-backup 3/3] api: backup: disallow incremental backups with different index length

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

On 3/10/26 5:09 PM, Robert Obkircher wrote:
> Restore the previous restrictions because fixed index files are only
> reused for qemu backups where the total size never changes.
> 

Fixes: 28fb8143 ("api: backup: make fixed index file size optional")

> Signed-off-by: Robert Obkircher <r.obkircher@proxmox.com>
> ---
>   src/api2/backup/mod.rs | 13 +++++++++++++
>   1 file changed, 13 insertions(+)
> 
> diff --git a/src/api2/backup/mod.rs b/src/api2/backup/mod.rs
> index 3c044c78..4a37947b 100644
> --- a/src/api2/backup/mod.rs
> +++ b/src/api2/backup/mod.rs
> @@ -498,6 +498,11 @@ fn create_fixed_index(
>       let mut incremental = false;
>       if let Some(csum) = reuse_csum {
>           incremental = true;
> +
> +        if size.is_none() {
> +            bail!("size is required for incremental backups");
> +        }
> +
>           let last_backup = match &env.last_backup {
>               Some(info) => info,
>               None => {
> @@ -531,6 +536,14 @@ fn create_fixed_index(
>       let mut writer = env.datastore.create_fixed_writer(&path, size, chunk_size)?;
>   
>       if let Some(reader) = reader {
> +        // compares chunk count instead of size for backwards compatability

typo: s/compatability/compatibility

> +        if writer.index_length() != reader.index_count() {
> +            bail!(
> +                "cannot reuse index - index sizes not equal ({} != {})",
> +                writer.index_length(),
> +                reader.index_count()
> +            );
> +        }
>           writer.clone_data_from(&reader)?;
>       }
>