Add a cancel callback and batch abort flag so auto-mount-all stops after dialog cancellation.
Mark MountVolume ERR_USER_ABORT with ERROR_CANCELLED so external /cancelmount also stops the scan.
Add a root-driver abort IOCTL that bypasses the mount control mutex and sets cooperative KDF abort flags for the active mount.
Restrict abort requests to privileged callers or to the user that initiated the pending mount, and retry early wait-dialog cancel requests until the driver has registered the cancellable mount context.
Wire the wait dialog Cancel button to send the abort request through a fresh driver handle, and propagate ERR_USER_ABORT through header/cache processing.
Add a /cancelmount command-line switch that sends the same abort request without displaying UI, so users can cancel hidden-wait-dialog mount operations from another process.
Mounir IDRASSI