Structure needs cleaning / Directory block does not have space for checksum

[Gregor Zattler <telegraph@gmx.net>]

Dear debian enthusiasts, I use
rdiff-backup, which now is not able to
work with my most precious backup,
instead throws a python backtrace which
contains:

OSError: [Errno 117] Structure needs cleaning: b'/mnt/mic-backup/rdiff-backup/durable/rdiff-backup-data/increments/home/grfz/.procmail/backup-post-mailmunge/new'

While a fsck.ext4 -vvvtfDfy on that file
system gives

Failed to optimize directory /rdiff-backup/durable/rdiff-backup-data/increments/home/grfz/.procmail/backup-post-mailmunge/new (498074110): Directory block does not have space for checksum

in Pass 3A: Optimizing directories.


Because of
https://blogs.oracle.com/linux/post/space-management-with-large-directories-in-ext4
I tried to copy said directory:

cp -a new neu

this too does not work:

cp: cannot access 'new': Structure needs cleaning
cp: preserving times for 'neu': Read-only file system

Any ideas how to repair said directory,
clean the structure, or another work
around to at least get rdiff-backup get
to use the backup again for restoring?

Or where to ask?   The ext3-users
mailing list does not exist any more?

Or how to avoid such a problem next time?



Thanks in advance for any hints, Gregor