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Commit df1d80a9 authored by Rasmus Villemoes's avatar Rasmus Villemoes Committed by Linus Torvalds
Browse files

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: default avatarRasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b26ad583

lib/bitmap.c

+6 −16
Original line number Diff line number Diff line
@@ -744,10 +744,10 @@ EXPORT_SYMBOL(bitmap_parselist_user); 
/**

 * 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 @@ EXPORT_SYMBOL(bitmap_parselist_user); 
 *

 * 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);

}



/**