lib/bitmap.c: simplify bitmap_pos_to_ord
The ordinal of a set bit is simply the number of set bits before it;
counting those doesn't need to be done one bit at a time. While at it,
update the parameters to unsigned int.
It is not completely unthinkable that gcc would see pos as compile-time
constant 0 in one of the uses of bitmap_pos_to_ord. Since the static
inline frontend bitmap_weight doesn't handle nbits==0 correctly (it would
behave exactly as if nbits==BITS_PER_LONG), use __bitmap_weight.
Alternatively, the last line could be spelled bitmap_weight(buf, pos+1)-1,
but this is simpler.
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>
diff --git a/lib/bitmap.c b/lib/bitmap.c
index b0d3e823..84d20b5 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -744,10 +744,10 @@
/**
* bitmap_pos_to_ord - find ordinal of set bit at given position in bitmap
* @buf: pointer to a bitmap
- * @pos: a bit position in @buf (0 <= @pos < @bits)
- * @bits: number of valid bit positions in @buf
+ * @pos: a bit position in @buf (0 <= @pos < @nbits)
+ * @nbits: number of valid bit positions in @buf
*
- * Map the bit at position @pos in @buf (of length @bits) to the
+ * Map the bit at position @pos in @buf (of length @nbits) to the
* ordinal of which set bit it is. If it is not set or if @pos
* is not a valid bit position, map to -1.
*
@@ -759,22 +759,12 @@
*
* The bit positions 0 through @bits are valid positions in @buf.
*/
-static int bitmap_pos_to_ord(const unsigned long *buf, int pos, int bits)
+static int bitmap_pos_to_ord(const unsigned long *buf, unsigned int pos, unsigned int nbits)
{
- int i, ord;
-
- if (pos < 0 || pos >= bits || !test_bit(pos, buf))
+ if (pos >= nbits || !test_bit(pos, buf))
return -1;
- i = find_first_bit(buf, bits);
- ord = 0;
- while (i < pos) {
- i = find_next_bit(buf, bits, i + 1);
- ord++;
- }
- BUG_ON(i != pos);
-
- return ord;
+ return __bitmap_weight(buf, pos);
}
/**
