Hello all,
	It appears that the CLEAR_BITMAP() macro in include/linux/types.h is 
broken.

(Examples done with BITS_PER_LONG == 32, but would work with == 64, or 
anything but 8 for that matter! :)

 >#define DECLARE_BITMAP(name,bits) \
 >	unsigned long name[((bits)+BITS_PER_LONG-1)/BITS_PER_LONG]
 >#define CLEAR_BITMAP(name,bits) \
 >	memset(name, 0, ((bits)+BITS_PER_LONG-1)/8)

If, for example, we DECLARE_BITMAP(foo, 64), we're going to get:
	unsigned long foo[((64)+32-1)/32] =>
	unsigned long foo[95/32] =>
	unsigned long foo[2]

Now, that's all well and good (and correct! ;)  But, look at what 
happens if we do a CLEAR_BITMAP(foo, 64):
	memset(foo, 0, ((64)+32-1)/8) =>
	memset(foo, 0, 95/8) =>
	memset(foo, 0, 11)

So the memset is going to try and clear 11 bytes starting at foo, which 
will overflow the foo array by 3 bytes.  This is bad.

What CLEAR_BITMAP wants to be doing is this:
  #define CLEAR_BITMAP(name,bits) \
  	memset(name, 0, 
(((bits)+BITS_PER_LONG-1)/BITS_PER_LONG)*sizeof(unsigned long))

Attatched is a patch that creates a macro BITS_TO_LONGS that just rounds 
a number of bits up to the closest number of unsigned longs.  This makes 
the DECLARE & CLEAR _BITMAP macros more readable.  I also modify the 
CLEAR_BITMAP macro to work correctly.

Cheers!

-Matt