"It doesn't work now so it clearly isnt being used 8). We hold the lock
because its a proc function and we then replace the proc functions in the
attach method -> deadlock. It is also incredibly hard to fix without a
major rewrite."
The same is true for HDIO_SET_IDE_SCSI ioctl.
Both were broken 18 months ago in 2.5.63 as a side-effect of locking fixes.