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Subject[PATCH 7/8] lib: bitmap: Simplify bitmap_ord_to_pos
Date
Make the return value and the ord and nbits parameters of
bitmap_ord_to_pos unsigned.

Also, simplify the implementation and as a side effect make the result
fully defined, returning nbits for ord >= weight, in analogy with what
find_{first,next}_bit does. This is a better sentinel than the former
("unofficial") 0. No current users are affected by this change.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
include/linux/bitmap.h | 2 +-
lib/bitmap.c | 28 +++++++++++-----------------
2 files changed, 12 insertions(+), 18 deletions(-)

diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index 85e8fb091ed7..e854934cdbf9 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -144,7 +144,7 @@ extern int bitmap_find_free_region(unsigned long *bitmap, unsigned int bits, int
extern void bitmap_release_region(unsigned long *bitmap, unsigned int pos, int order);
extern int bitmap_allocate_region(unsigned long *bitmap, unsigned int pos, int order);
extern void bitmap_copy_le(void *dst, const unsigned long *src, int nbits);
-extern int bitmap_ord_to_pos(const unsigned long *bitmap, int n, int bits);
+extern unsigned int bitmap_ord_to_pos(const unsigned long *bitmap, unsigned int ord, unsigned int nbits);

#define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) % BITS_PER_LONG))
#define BITMAP_LAST_WORD_MASK(nbits) \
diff --git a/lib/bitmap.c b/lib/bitmap.c
index ab62a7e4d50f..89b61e42f173 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -740,34 +740,28 @@ static int bitmap_pos_to_ord(const unsigned long *buf, unsigned int pos, unsigne
* bitmap_ord_to_pos - find position of n-th set bit in bitmap
* @buf: pointer to bitmap
* @ord: ordinal bit position (n-th set bit, n >= 0)
- * @bits: number of valid bit positions in @buf
+ * @nbits: number of valid bit positions in @buf
*
* Map the ordinal offset of bit @ord in @buf to its position in @buf.
- * Value of @ord should be in range 0 <= @ord < weight(buf), else
- * results are undefined.
+ * Value of @ord should be in range 0 <= @ord < weight(buf). If @ord
+ * >= weight(buf), returns @nbits.
*
* If for example, just bits 4 through 7 are set in @buf, then @ord
* values 0 through 3 will get mapped to 4 through 7, respectively,
- * and all other @ord values return undefined values. When @ord value 3
+ * and all other @ord values returns @nbits. When @ord value 3
* gets mapped to (returns) @pos value 7 in this example, that means
* that the 3rd set bit (starting with 0th) is at position 7 in @buf.
*
- * The bit positions 0 through @bits are valid positions in @buf.
+ * The bit positions 0 through @nbits-1 are valid positions in @buf.
*/
-int bitmap_ord_to_pos(const unsigned long *buf, int ord, int bits)
+unsigned int bitmap_ord_to_pos(const unsigned long *buf, unsigned int ord, unsigned int nbits)
{
- int pos = 0;
+ unsigned int pos;

- if (ord >= 0 && ord < bits) {
- int i;
-
- for (i = find_first_bit(buf, bits);
- i < bits && ord > 0;
- i = find_next_bit(buf, bits, i + 1))
- ord--;
- if (i < bits && ord == 0)
- pos = i;
- }
+ for (pos = find_first_bit(buf, nbits);
+ pos < nbits && ord;
+ pos = find_next_bit(buf, nbits, pos + 1))
+ ord--;

return pos;
}
--
2.1.3


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