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lib/bitmap.c: simplify bitmap_pos_to_ord

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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>
This commit is contained in:
Rasmus Villemoes 2015-02-12 15:02:07 -08:00 • committed by Linus Torvalds
parent b26ad5836c
commit df1d80a9eb
1 changed files with 6 additions and 16 deletions
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22
lib/bitmap.c
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@ -744,10 +744,10 @@ EXPORT_SYMBOL(bitmap_parselist_user);
/** /**
* bitmap_pos_to_ord - find ordinal of set bit at given position in bitmap * bitmap_pos_to_ord - find ordinal of set bit at given position in bitmap
* @buf: pointer to a bitmap * @buf: pointer to a bitmap
* @pos: a bit position in @buf (0 <= @pos < @bits) * @pos: a bit position in @buf (0 <= @pos < @nbits)
* @bits: number of valid bit positions in @buf * @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 * ordinal of which set bit it is. If it is not set or if @pos
* is not a valid bit position, map to -1. * 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. * 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 >= nbits || !test_bit(pos, buf))
if (pos < 0 || pos >= bits || !test_bit(pos, buf))
return -1; return -1;
i = find_first_bit(buf, bits); return __bitmap_weight(buf, pos);
ord = 0;
while (i < pos) {
i = find_next_bit(buf, bits, i + 1);
ord++;
}
BUG_ON(i != pos);
return ord;
} }
/** /**