cinder volume delete fails with "ImageBusy error raised while deleting rbd volume. This may have been caused by a connection from a client that has crashed and, if so, may be resolved by retrying the delete after 30 seconds has elapsed."

Issue

• cinder volume delete fails with "ImageBusy error raised while deleting rbd volume. This may have been caused by a connection from a client that has crashed and, if so, may be resolved by retrying the delete after 30 seconds has elapsed."
• volume.log shows below error.

2018-04-09 16:12:47.521 556167 WARNING cinder.volume.drivers.rbd [req-c277a265-7c9a-4121-8298-646d9ccf6ad5 2f0b175836704cf5b2df5d5015caca32 c175ea0037194d96936c7d07c38070a6 - default default] ImageBusy error raised while deleting rbd volume. This may have been caused by a connection from a client that has crashed and, if so, may be resolved by retrying the delete after 30 seconds has elapsed. 2018-04-09 16:12:47.525 556167 ERROR cinder.volume.manager [req-c277a265-7c9a-4121-8298-646d9ccf6ad5 2f0b175836704cf5b2df5d5015caca32 c175ea0037194d96936c7d07c38070a6 - default default] Unable to delete busy volume.