How to reclaim space in a thin provisioned LUN using fstrim?

Issue

• Thin provisioned LUN returns an allocation error, even though the df command says the device has free space:

kernel: blk_update_request: critical space allocation error, dev sdb, sector 426379264
kernel: blk_update_request: critical space allocation error, dev dm-2, sector 426379264
kernel: sd 12:0:2:1: [sdh] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
kernel: sd 12:0:2:1: [sdh] tag#0 Sense Key : Data Protect [current]
kernel: sd 12:0:2:1: [sdh] tag#0 Add. Sense: Space allocation failed write protect
kernel: sd 12:0:2:1: [sdh] tag#0 CDB: Write(10) 2a 00 16 9d a1 90 00 00 08 00
kernel: blk_update_request: critical space allocation error, dev sdh, sector 379429264
kernel: sd 11:0:3:1: [sdd] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
kernel: sd 11:0:3:1: [sdd] tag#0 Sense Key : Data Protect [current]
kernel: sd 11:0:3:1: [sdd] tag#0 Add. Sense: Space allocation failed write protect