Commit 930ae745 authored by Akinobu Mita's avatar Akinobu Mita Committed by Linus Torvalds
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[PATCH] bitops: generic ext2_{set,clear,test,find_first_zero,find_next_zero}_bit()

This patch introduces the C-language equivalents of the functions below:

int ext2_set_bit(int nr, volatile unsigned long *addr);
int ext2_clear_bit(int nr, volatile unsigned long *addr);
int ext2_test_bit(int nr, const volatile unsigned long *addr);
unsigned long ext2_find_first_zero_bit(const unsigned long *addr,
                                       unsigned long size);
unsinged long ext2_find_next_zero_bit(const unsigned long *addr,
                                      unsigned long size);

In include/asm-generic/bitops/ext2-non-atomic.h

This code largely copied from:

Signed-off-by: default avatarAkinobu Mita <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent a54baa14
#include <asm-generic/bitops/le.h>
#define ext2_set_bit(nr,addr) \
generic___test_and_set_le_bit((nr),(unsigned long *)(addr))
#define ext2_clear_bit(nr,addr) \
generic___test_and_clear_le_bit((nr),(unsigned long *)(addr))
#define ext2_test_bit(nr,addr) \
generic_test_le_bit((nr),(unsigned long *)(addr))
#define ext2_find_first_zero_bit(addr, size) \
generic_find_first_zero_le_bit((unsigned long *)(addr), (size))
#define ext2_find_next_zero_bit(addr, size, off) \
generic_find_next_zero_le_bit((unsigned long *)(addr), (size), (off))
#include <asm/types.h>
#include <asm/byteorder.h>
#define BITOP_WORD(nr) ((nr) / BITS_PER_LONG)
#define BITOP_LE_SWIZZLE ((BITS_PER_LONG-1) & ~0x7)
#if defined(__LITTLE_ENDIAN)
#define generic_test_le_bit(nr, addr) test_bit(nr, addr)
#define generic___set_le_bit(nr, addr) __set_bit(nr, addr)
#define generic___clear_le_bit(nr, addr) __clear_bit(nr, addr)
#define generic_test_and_set_le_bit(nr, addr) test_and_set_bit(nr, addr)
#define generic_test_and_clear_le_bit(nr, addr) test_and_clear_bit(nr, addr)
#define generic___test_and_set_le_bit(nr, addr) __test_and_set_bit(nr, addr)
#define generic___test_and_clear_le_bit(nr, addr) __test_and_clear_bit(nr, addr)
#define generic_find_next_zero_le_bit(addr, size, offset) find_next_zero_bit(addr, size, offset)
#elif defined(__BIG_ENDIAN)
#define generic_test_le_bit(nr, addr) \
test_bit((nr) ^ BITOP_LE_SWIZZLE, (addr))
#define generic___set_le_bit(nr, addr) \
__set_bit((nr) ^ BITOP_LE_SWIZZLE, (addr))
#define generic___clear_le_bit(nr, addr) \
__clear_bit((nr) ^ BITOP_LE_SWIZZLE, (addr))
#define generic_test_and_set_le_bit(nr, addr) \
test_and_set_bit((nr) ^ BITOP_LE_SWIZZLE, (addr))
#define generic_test_and_clear_le_bit(nr, addr) \
test_and_clear_bit((nr) ^ BITOP_LE_SWIZZLE, (addr))
#define generic___test_and_set_le_bit(nr, addr) \
__test_and_set_bit((nr) ^ BITOP_LE_SWIZZLE, (addr))
#define generic___test_and_clear_le_bit(nr, addr) \
__test_and_clear_bit((nr) ^ BITOP_LE_SWIZZLE, (addr))
extern unsigned long generic_find_next_zero_le_bit(const unsigned long *addr,
unsigned long size, unsigned long offset);
#error "Please fix <asm/byteorder.h>"
#define generic_find_first_zero_le_bit(addr, size) \
generic_find_next_zero_le_bit((addr), (size), 0)
#endif /* _ASM_GENERIC_BITOPS_LE_H_ */
......@@ -12,6 +12,7 @@
#include <linux/bitops.h>
#include <linux/module.h>
#include <asm/types.h>
#include <asm/byteorder.h>
#define BITOP_WORD(nr) ((nr) / BITS_PER_LONG)
......@@ -106,3 +107,75 @@ unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
#ifdef __BIG_ENDIAN
/* include/linux/byteorder does not support "unsigned long" type */
static inline unsigned long ext2_swabp(const unsigned long * x)
#if BITS_PER_LONG == 64
return (unsigned long) __swab64p((u64 *) x);
#elif BITS_PER_LONG == 32
return (unsigned long) __swab32p((u32 *) x);
#error BITS_PER_LONG not defined
/* include/linux/byteorder doesn't support "unsigned long" type */
static inline unsigned long ext2_swab(const unsigned long y)
#if BITS_PER_LONG == 64
return (unsigned long) __swab64((u64) y);
#elif BITS_PER_LONG == 32
return (unsigned long) __swab32((u32) y);
#error BITS_PER_LONG not defined
unsigned long generic_find_next_zero_le_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 - 1UL);
if (offset) {
tmp = ext2_swabp(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_swap;
result += BITS_PER_LONG;
size -= BITS_PER_LONG;
if (!size)
return result;
tmp = ext2_swabp(p);
tmp |= ~0UL << size;
if (tmp == ~0UL) /* Are any bits zero? */
return result + size; /* Nope. Skip ffz */
return result + ffz(tmp);
return result + ffz(ext2_swab(tmp));
#endif /* __BIG_ENDIAN */
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