[PATCH -mmotm -v2] Fix

Akinobu Mita
2009-10-15T06:07:07Z

From: Akinobu Mita <akinobu.mita@gmail.com>
Subject: Fix bitmap-introduce-bitmap_set-bitmap_clear-bitmap_find_next_zero_area.patch

- Rewrite bitmap_set and bitmap_clear

Instead of setting or clearing for each bit.

- Fix off-by-one errors in bitmap_find_next_zero_area

This bug was derived from find_next_zero_area in iommu-helper.

- Add kerneldoc for bitmap_find_next_zero_area

This patch is supposed to be folded into
bitmap-introduce-bitmap_set-bitmap_clear-bitmap_find_next_zero_area.patch

* -v2
- Remove an extra test at the "index" value by find_next_bit

Index was just returned by find_next_zero_bit, so we know it's zero.

Noticed-by: Kyle Hubert <khubert@gmail.com>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
---
lib/bitmap.c | 62 ++++++++++++++++++++++++++++++++++++++++++++-------------
1 files changed, 48 insertions(+), 14 deletions(-)

diff --git a/lib/bitmap.c b/lib/bitmap.c
index 2415da4..962b863 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -271,28 +271,62 @@ int __bitmap_weight(const unsigned long *bitmap, int bits)
}
EXPORT_SYMBOL(__bitmap_weight);

-void bitmap_set(unsigned long *map, int i, int len)
-{
- int end = i + len;
+#define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) % BITS_PER_LONG))

- while (i < end) {
- __set_bit(i, map);
- i++;
+void bitmap_set(unsigned long *map, int start, int nr)
+{
+ unsigned long *p = map + BIT_WORD(start);
+ const int size = start + nr;
+ int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
+ unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
+
+ while (nr - bits_to_set >= 0) {
+ *p |= mask_to_set;
+ nr -= bits_to_set;
+ bits_to_set = BITS_PER_LONG;
+ mask_to_set = ~0UL;
+ p++;
+ }
+ if (nr) {
+ mask_to_set &= BITMAP_LAST_WORD_MASK(size);
+ *p |= mask_to_set;
}
}
EXPORT_SYMBOL(bitmap_set);

void bitmap_clear(unsigned long *map, int start, int nr)
{
- int end = start + nr;
-
- while (start < end) {
- __clear_bit(start, map);
- start++;
+ unsigned long *p = map + BIT_WORD(start);
+ const int size = start + nr;
+ int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
+ unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);
+
+ while (nr - bits_to_clear >= 0) {
+ *p &= ~mask_to_clear;
+ nr -= bits_to_clear;
+ bits_to_clear = BITS_PER_LONG;
+ mask_to_clear = ~0UL;
+ p++;
+ }
+ if (nr) {
+ mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
+ *p &= ~mask_to_clear;
}
}
EXPORT_SYMBOL(bitmap_clear);

+/*
+ * bitmap_find_next_zero_area - find a contiguous aligned zero area
+ * @map: The address to base the search on
+ * @size: The bitmap size in bits
+ * @start: The bitnumber to start searching at
+ * @nr: The number of zeroed bits we're looking for
+ * @align_mask: Alignment mask for zero area
+ *
+ * The @align_mask should be one less than a power of 2; the effect is that
+ * the bit offset of all zero areas this function finds is multiples of that
+ * power of 2. A @align_mask of 0 means no alignment is required.
+ */
unsigned long bitmap_find_next_zero_area(unsigned long *map,
unsigned long size,
unsigned long start,
@@ -304,12 +338,12 @@ again:
index = find_next_zero_bit(map, size, start);

/* Align allocation */
- index = (index + align_mask) & ~align_mask;
+ index = __ALIGN_MASK(index, align_mask);

end = index + nr;
- if (end >= size)
+ if (end > size)
return end;
- i = find_next_bit(map, end, index);
+ i = find_next_bit(map, end, index + 1);
if (i < end) {
start = i + 1;
goto again;
--
1.5.4.3