Staging: ramzswap: Handle case for invalid backing swap
Currently, we crash (issue BUG_ON) if backing swap
disk size is zero. This can happen is user specified
an extended partition or simply a bad disk as backing
swap. A crash is really an unpleasant surprise to user
for such trivial problems.
Now, we check for this condition and simply fail device
initialization if this is the case.
Additional cleanups:
* use static for all functions
* remove extra newline between functions
* memset backing_swap_name to NULL on device reset