There are two cases where the 'length' in the backup block may be larger than the block size today. Specifically, the length is equal to the file size in these two cases.

1. On the first full incremental backup, the length will be equal to the file size for all files regardless of the specified block size.
2. On subsequent incremental backups when a new file needs to be copied, then the length will be equal to the file size for that file, regardless of the specified block size.

Users are responsible for not reading past the file size as the last (offset, length) backup block pair may go past the file size.