I have a system that creates periodic btrfs snapshots and deletes old ones. Today, I've started receiving warnings that the system can't delete some old snapshots.
This is the output I get:
root@machine:/path# btrfs sub del 2014-10-26--01-50-01-@ten_minutely Delete subvolume '/path/2014-10-26--01-50-01-@ten_minutely' ERROR: cannot delete '/path/2014-10-26--01-50-01-@ten_minutely'
I can create and delete new snapshots without a problem - just a couple of them, created today, exhibit this behaviour.
The permissions look ok.
Syslog show nothing related.
btrfs filesystem df, and there's space available for the filesystem - both for metadata and data.
A strace of the delete command shows:
#... ioctl(3, 0x5000940f, 0xffa1d1f0) = -1 ENOTEMPTY (Directory not empty) close(3) = 0 #...
What further steps can I take to investigate the cause?