lib: bitmap: change bitmap_shift_left to take unsigned parameters

gcc can generate slightly better code for stuff like "nbits %
BITS_PER_LONG" when it knows nbits is not negative.  Since negative size
bitmaps or shift amounts don't make sense, change these parameters of
bitmap_shift_right to unsigned.

If off >= lim (which requires shift >= nbits), k is initialized with a
large positive value, but since I've let k continue to be signed, the loop
will never run and dst will be zeroed as expected.  Inside the loop, k is
guaranteed to be non-negative, so the fact that it is promoted to unsigned
in the various expressions it appears in is harmless.

Also use "shift" and "nbits" consistently for the parameter names.
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

@@ -98,8 +98,8 @@ extern void __bitmap_complement(unsigned long *dst, const unsigned long *src,
 			unsigned int nbits);
 extern void __bitmap_shift_right(unsigned long *dst, const unsigned long *src,
 				unsigned int shift, unsigned int nbits);
-extern void __bitmap_shift_left(unsigned long *dst,
-                        const unsigned long *src, int shift, int bits);
+extern void __bitmap_shift_left(unsigned long *dst, const unsigned long *src,
+				unsigned int shift, unsigned int nbits);
 extern int __bitmap_and(unsigned long *dst, const unsigned long *bitmap1,
 			const unsigned long *bitmap2, unsigned int nbits);
 extern void __bitmap_or(unsigned long *dst, const unsigned long *bitmap1,
@@ -322,13 +322,13 @@ static inline void bitmap_shift_right(unsigned long *dst, const unsigned long *s
 		__bitmap_shift_right(dst, src, shift, nbits);
 }
 
-static inline void bitmap_shift_left(unsigned long *dst,
-			const unsigned long *src, int n, int nbits)
+static inline void bitmap_shift_left(unsigned long *dst, const unsigned long *src,
+				unsigned int shift, unsigned int nbits)
 {
 	if (small_const_nbits(nbits))
-		*dst = (*src << n) & BITMAP_LAST_WORD_MASK(nbits);
+		*dst = (*src << shift) & BITMAP_LAST_WORD_MASK(nbits);
 	else
-		__bitmap_shift_left(dst, src, n, nbits);
+		__bitmap_shift_left(dst, src, shift, nbits);
 }
 
 static inline int bitmap_parse(const char *buf, unsigned int buflen,

lib/bitmap.c

@@ -148,18 +148,19 @@ EXPORT_SYMBOL(__bitmap_shift_right);
  *   @dst : destination bitmap
  *   @src : source bitmap
  *   @shift : shift by this many bits
- *   @bits : bitmap size, in bits
+ *   @nbits : bitmap size, in bits
  *
  * Shifting left (multiplying) means moving bits in the LS -> MS
  * direction.  Zeros are fed into the vacated LS bit positions
  * and those MS bits shifted off the top are lost.
  */
 
-void __bitmap_shift_left(unsigned long *dst,
-			const unsigned long *src, int shift, int bits)
+void __bitmap_shift_left(unsigned long *dst, const unsigned long *src,
+			unsigned int shift, unsigned int nbits)
 {
-	int k, lim = BITS_TO_LONGS(bits), left = bits % BITS_PER_LONG;
-	int off = shift/BITS_PER_LONG, rem = shift % BITS_PER_LONG;
+	int k;
+	unsigned int lim = BITS_TO_LONGS(nbits), left = nbits % BITS_PER_LONG;
+	unsigned int off = shift/BITS_PER_LONG, rem = shift % BITS_PER_LONG;
 	for (k = lim - off - 1; k >= 0; --k) {
 		unsigned long upper, lower;