lib: bitmap: add missing mask in bitmap_andnot

Apparently, bitmap_andnot is supposed to return whether the new bitmap
is empty.  But it didn't take potential garbage bits in the last word
into account.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/bitmap.h

@@ -217,7 +217,7 @@ static inline int bitmap_andnot(unsigned long *dst, const unsigned long *src1,
 			const unsigned long *src2, unsigned int nbits)
 {
 	if (small_const_nbits(nbits))
-		return (*dst = *src1 & ~(*src2)) != 0;
+		return (*dst = *src1 & ~(*src2) & BITMAP_LAST_WORD_MASK(nbits)) != 0;
 	return __bitmap_andnot(dst, src1, src2, nbits);
 }
 

lib/bitmap.c

@@ -223,11 +223,14 @@ int __bitmap_andnot(unsigned long *dst, const unsigned long *bitmap1,
 				const unsigned long *bitmap2, unsigned int bits)
 {
 	unsigned int k;
-	unsigned int nr = BITS_TO_LONGS(bits);
+	unsigned int lim = bits/BITS_PER_LONG;
 	unsigned long result = 0;
 
-	for (k = 0; k < nr; k++)
+	for (k = 0; k < lim; k++)
 		result |= (dst[k] = bitmap1[k] & ~bitmap2[k]);
+	if (bits % BITS_PER_LONG)
+		result |= (dst[k] = bitmap1[k] & ~bitmap2[k] &
+			   BITMAP_LAST_WORD_MASK(bits));
 	return result != 0;
 }
 EXPORT_SYMBOL(__bitmap_andnot);