The LFS attempts to cancel an outstanding operation with vn_cancel. There are two types of vn_cancel: normal and forced.

• A normal vn_cancel only flows to the PFS between Part 1 and Part 2, and is used to get requests off the waiting, or blocking, queues in the PFS. If the request is not currently on a waiting queue, nothing is done. If the request is found, it is removed from the queue and failed with ECANCELED.
• A forced vn_cancel is used during process termination of the original requestor. It can be sent logically at any time, but the PFS will already have abnormally ended and gone through recovery if the request was in Part 1 or Part 2 at the time the process terminated. There is no Part 2 after a vn_cancel force, so the PFS must do any necessary cleanup during the vn_cancel.