bitmap_find_free_region — find a contiguous aligned mem region
| int bitmap_find_free_region ( | unsigned long * bitmap, | 
| unsigned int bits, | |
| int order ); | 
bitmaparray of unsigned longs corresponding to the bitmap
bitsnumber of bits in the bitmap
orderregion size (log base 2 of number of bits) to find
   Find a region of free (zero) bits in a bitmap of bits bits and
   allocate them (set them to one).  Only consider regions of length
   a power (order) of two, aligned to that power of two, which
   makes the search algorithm much faster.
   
Return the bit offset in bitmap of the allocated region, or -errno on failure.