lib/bitmap.c: simplify bitmap_pos_to_ord (df1d80a9) · Commits · 戴 / test

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>

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);
		}

		/**

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