BTRFS Subvolume/snapshot marked as DELETED

If you see entries like this after you delete a subvolume:

ID 10348 gen 470306 top level 0 path DELETED
ID 10408 gen 470171 top level 0 path DELETED
ID 10409 gen 465270 top level 0 path DELETED

Dont worry, first off you get 1 entry per deleted subvolume, the task goes on in the background. Over time, they will go away (how much time? not long)

Here you can monitor it like this

Note my mount point for my btrfs volume is /Sally:

while true; do echo "[`date`] number of DELETED enteries: `btrfs subvolume list /Sally | grep DELETED | wc -l`"; sleep 1;  done;

# OUTPUT:
# [Mon May 19 21:17:30 PDT 2014] number of DELETED enteries: 52
# [Mon May 19 21:17:40 PDT 2014] number of DELETED enteries: 47
# [Mon May 19 21:17:50 PDT 2014] number of DELETED enteries: 47
# [Mon May 19 21:18:00 PDT 2014] number of DELETED enteries: 47
# [Mon May 19 21:18:11 PDT 2014] number of DELETED enteries: 42
# [Mon May 19 21:18:21 PDT 2014] number of DELETED enteries: 42
# [Mon May 19 21:18:31 PDT 2014] number of DELETED enteries: 42
# [Mon May 19 21:18:41 PDT 2014] number of DELETED enteries: 42
# ... and so on until time frees them all ...