Re: [PATCH 2/8] bitmap: Introduce bitmap_set, bitmap_clear,

Akinobu Mita
2009-10-14T03:39:39Z

On Wed, Oct 14, 2009 at 08:54:47AM +1100, Michael Ellerman wrote:
> On Tue, 2009-10-13 at 18:10 +0900, Akinobu Mita wrote:
> > My user space testing exposed off-by-one error find_next_zero_area
> > in iommu-helper.
>
> Why not merge those tests into the kernel as a configurable boot-time
> self-test?

I send the test program that I used. Obviously it needs
better diagnostic messages and cleanup to be added into kernel tests.

#include <stdio.h>
#include <time.h>
#include <stdlib.h>
#include <string.h>

#if 1 /* Copy and paste from kernel source */

#define BITS_PER_BYTE 8
#define BITS_PER_LONG (sizeof(long) * BITS_PER_BYTE)

#define BIT_WORD(nr) ((nr) / BITS_PER_LONG)
#define BITOP_WORD(nr) ((nr) / BITS_PER_LONG)

#define BITMAP_LAST_WORD_MASK(nbits) \
( \
((nbits) % BITS_PER_LONG) ? \
(1UL<<((nbits) % BITS_PER_LONG))-1 : ~0UL \
)

#define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) % BITS_PER_LONG))

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;
}
}

void bitmap_clear(unsigned long *map, int start, int nr)
{
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;
}
}

static unsigned long __ffs(unsigned long word)
{
int num = 0;

if ((word & 0xffff) = 0) {
num += 16;
word >>= 16;
}
if ((word & 0xff) = 0) {
num += 8;
word >>= 8;
}
if ((word & 0xf) = 0) {
num += 4;
word >>= 4;
}
if ((word & 0x3) = 0) {
num += 2;
word >>= 2;
}
if ((word & 0x1) = 0)
num += 1;
return num;
}

unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
unsigned long offset)
{
const unsigned long *p = addr + BITOP_WORD(offset);
unsigned long result = offset & ~(BITS_PER_LONG-1);
unsigned long tmp;

if (offset >= size)
return size;
size -= result;
offset %= BITS_PER_LONG;
if (offset) {
tmp = *(p++);
tmp &= (~0UL << offset);
if (size < BITS_PER_LONG)
goto found_first;
if (tmp)
goto found_middle;
size -= BITS_PER_LONG;
result += BITS_PER_LONG;
}
while (size & ~(BITS_PER_LONG-1)) {
if ((tmp = *(p++)))
goto found_middle;
result += BITS_PER_LONG;
size -= BITS_PER_LONG;
}
if (!size)
return result;
tmp = *p;

found_first:
tmp &= (~0UL >> (BITS_PER_LONG - size));
if (tmp = 0UL) /* Are any bits set? */
return result + size; /* Nope. */
found_middle:
return result + __ffs(tmp);
}

#define ffz(x) __ffs(~(x))

unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
unsigned long offset)
{
const unsigned long *p = addr + BITOP_WORD(offset);
unsigned long result = offset & ~(BITS_PER_LONG-1);
unsigned long tmp;

if (offset >= size)
return size;
size -= result;
offset %= BITS_PER_LONG;
if (offset) {
tmp = *(p++);
tmp |= ~0UL >> (BITS_PER_LONG - offset);
if (size < BITS_PER_LONG)
goto found_first;
if (~tmp)
goto found_middle;
size -= BITS_PER_LONG;
result += BITS_PER_LONG;
}
while (size & ~(BITS_PER_LONG-1)) {
if (~(tmp = *(p++)))
goto found_middle;
result += BITS_PER_LONG;
size -= BITS_PER_LONG;
}
if (!size)
return result;
tmp = *p;

found_first:
tmp |= ~0UL << size;
if (tmp = ~0UL) /* Are any bits zero? */
return result + size; /* Nope. */
found_middle:
return result + ffz(tmp);
}

#define __ALIGN_MASK(x,mask) (((x)+(mask))&~(mask))

static inline int test_bit(int nr, const volatile unsigned long *addr)
{
return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));
}

unsigned long bitmap_find_next_zero_area(unsigned long *map,
unsigned long size,
unsigned long start,
unsigned int nr,
unsigned long align_mask)
{
unsigned long index, end, i;
again:
index = find_next_zero_bit(map, size, start);

/* Align allocation */
index = __ALIGN_MASK(index, align_mask);

end = index + nr;
#ifdef ORIGINAL
if (end >= size)
#else
if (end > size)
#endif
return end;

#ifdef ORIGINAL
for (i = index; i < end; i++) {
if (test_bit(i, map)) {
start = i+1;
goto again;
}
}
#else
i = find_next_bit(map, end, index);
if (i < end) {
start = i + 1;
goto again;
}
#endif
return index;
}

#define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d))
#define BITS_TO_LONGS(nr) DIV_ROUND_UP(nr, BITS_PER_BYTE * sizeof(long))
#define DECLARE_BITMAP(name,bits) unsigned long name[BITS_TO_LONGS(bits)]

#endif /* Copy and paste from kernel source */

static DECLARE_BITMAP(bitmap, 1000);
static DECLARE_BITMAP(empty, 1000);
static DECLARE_BITMAP(full, 1000);

static void bitmap_dump(unsigned long *bitmap, int size)
{
int i;

for (i = 0; i < size; i++) {
if (test_bit(i, bitmap))
printf("1 ");
else
printf("0 ");
if (i % 10 = 9)
printf("\n");
}
printf("\n");
}

static int test1(int size)
{

int start = random() % size;
int nr = random() % (size - start);

memset(bitmap, 0x00, BITS_TO_LONGS(size) * sizeof(unsigned long));

bitmap_set(bitmap, start, nr);
bitmap_clear(bitmap, start, nr);

if (memcmp(empty, bitmap, BITS_TO_LONGS(size) * sizeof(unsigned long)))
goto error;

return 0;
error:
bitmap_dump(bitmap, size);
return 1;
}

int test2(int size)
{
int start = random() % size;
int nr = random() % (size - start);

memset(bitmap, 0xff, BITS_TO_LONGS(size) * sizeof(unsigned long));

bitmap_clear(bitmap, start, nr);
bitmap_set(bitmap, start, nr);

if (memcmp(full, bitmap, BITS_TO_LONGS(size) * sizeof(unsigned long)))
goto error;

return 0;
error:
bitmap_dump(bitmap, size);
return 1;
}

int test3(int size)
{
int start = random() % size;
int nr = random() % (size - start);
unsigned long offset;

memset(bitmap, 0x00, BITS_TO_LONGS(size) * sizeof(unsigned long));
bitmap_set(bitmap, start, nr);
if (start) {
offset = bitmap_find_next_zero_area(bitmap, size, 0, start, 0);
if (offset != 0) {
printf("start %ld nr %ld\n", start, nr);
printf("offset %ld != 0\n", offset);
goto error;
}
}
offset = bitmap_find_next_zero_area(bitmap, size, start,
size - (start + nr), 0);
if (offset != start + nr) {
printf("start %ld nr %ld\n", start, nr);
printf("offset %ld != size + nr %ld\n", offset, start + nr);
goto error;
}

return 0;
error:
bitmap_dump(bitmap, size);

return 1;
}

int test4(int size)
{
int start = random() % size;
int nr = random() % (size - start);
unsigned long offset;

memset(bitmap, 0xff, BITS_TO_LONGS(size) * sizeof(unsigned long));
bitmap_clear(bitmap, start, nr);
offset = bitmap_find_next_zero_area(bitmap, size, start, nr, 0);
if (nr != 0) {
if (offset != start) {
printf("start %ld nr %ld\n", start, nr);
printf("offset %ld != start %ld\n", offset, start);
goto error;
}
}
return 0;
error:
bitmap_dump(bitmap, size);

return 1;
}

int main(int argc, char *argv[])
{
int err = 0;

srandom(time(NULL));

memset(empty, 0x00, sizeof(empty));
memset(full, 0xff, sizeof(full));

while (!err) {
err |= test1(1000);
err |= test2(1000);
err |= test3(1000);
err |= test4(1000);
}
return 0;
}