Ceph

When trying to load a series of backups from directories trees large and small, I noticed one particularly undesirable effect: the timestamps of directories within the snapshot tree appear to change, but only sometimes, when the corresponding directories are modified in some way I haven't been able to track down. I haven't come up with a reliable reproducer yet, but the way I've triggered the bug was like this:

for snapshot in 1 2 3 ...; do
  rsync -aHv --del /path/to/src/$snapshot/ /mnt/ceph/test/
  mkdir /mnt/ceph/test/.snap/$snapshot  # I actually use ..snap.. instead of .snap, in a ceph-fuse mount
done
# days later, after restarting mds and remounting (not sure either is needed to trigger the bug)
for snapshot in 1 2 3 ...; do
  rsync -aHv --del /path/to/src/$snapshot/ /mnt/ceph/test/.snap/$snapshot/ # fails to set times on various directories
done