Package: jdupes Version: 1.7-2 Severity: minor As currently implemented, jdupes(1) invokes FIDEDUPERANGE once for each set of files found to be duplicates. However, per documentation (say, [1]), there can be a filesystem-specific limit in place on how large a data span can be handled in a single call to FIDEDUPERANGE. Per strace(1) output, this limit appears to indeed be 16 MiB for Btrfs on Debian Stretch.
An obvious solution is to get the maximum of the bytes_deduped values returned by the call and invoke it again, advancing src_offset and dest_offset values by that maximum, possibly repeating these steps until the whole file length is covered. AFAICT, this issue is not solved as of recent Git (a32de0db, 2017-06-07.) [1] http://man7.org/linux/man-pages/man2/ioctl_fideduperange.2.html -- FSF associate member #7257 58F8 0F47 53F5 2EB2 F6A5 8916 3013 B6A0 230E 334A