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f2fs: introduce __find_rev_next(_zero)_bit

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When f2fs_set_bit is used, in a byte MSB and LSB is reversed,
in that case we can use __find_rev_next_bit or __find_rev_next_zero_bit.

Signed-off-by: Changman Lee <cm224.lee@samsung.com>
[Jaegeuk Kim: change the function names]
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
This commit is contained in:
Changman Lee 2013-11-15 10:42:51 +09:00 committed by Jaegeuk Kim
parent 413541dd66
commit 9a7f143ab5
1 changed files with 148 additions and 0 deletions
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148
fs/f2fs/segment.c
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@ -20,6 +20,154 @@
#include "node.h"
#include <trace/events/f2fs.h>
#define __reverse_ffz(x) __reverse_ffs(~(x))
/*
* __reverse_ffs is copied from include/asm-generic/bitops/__ffs.h since
* MSB and LSB are reversed in a byte by f2fs_set_bit.
*/
static inline unsigned long __reverse_ffs(unsigned long word)
{
int num = 0;
#if BITS_PER_LONG == 64
if ((word & 0xffffffff) == 0) {
num += 32;
word >>= 32;
}
#endif
if ((word & 0xffff) == 0) {
num += 16;
word >>= 16;
}
if ((word & 0xff) == 0) {
num += 8;
word >>= 8;
}
if ((word & 0xf0) == 0)
num += 4;
else
word >>= 4;
if ((word & 0xc) == 0)
num += 2;
else
word >>= 2;
if ((word & 0x2) == 0)
num += 1;
return num;
}
/*
* __find_rev_next(_zero)_bit is copied from lib/find_next_bit.c becasue
* f2fs_set_bit makes MSB and LSB reversed in a byte.
* Example:
* LSB <--> MSB
* f2fs_set_bit(0, bitmap) => 0000 0001
* f2fs_set_bit(7, bitmap) => 1000 0000
*/
static unsigned long __find_rev_next_bit(const unsigned long *addr,
unsigned long size, unsigned long offset)
{
const unsigned long *p = addr + BIT_WORD(offset);
unsigned long result = offset & ~(BITS_PER_LONG - 1);
unsigned long tmp;
unsigned long mask, submask;
unsigned long quot, rest;
if (offset >= size)
return size;
size -= result;
offset %= BITS_PER_LONG;
if (!offset)
goto aligned;
tmp = *(p++);
quot = (offset >> 3) << 3;
rest = offset & 0x7;
mask = ~0UL << quot;
submask = (unsigned char)(0xff << rest) >> rest;
submask <<= quot;
mask &= submask;
tmp &= mask;
if (size < BITS_PER_LONG)
goto found_first;
if (tmp)
goto found_middle;
size -= BITS_PER_LONG;
result += BITS_PER_LONG;
aligned:
while (size & ~(BITS_PER_LONG-1)) {
tmp = *(p++);
if (tmp)
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 + __reverse_ffs(tmp);
}
static unsigned long __find_rev_next_zero_bit(const unsigned long *addr,
unsigned long size, unsigned long offset)
{
const unsigned long *p = addr + BIT_WORD(offset);
unsigned long result = offset & ~(BITS_PER_LONG - 1);
unsigned long tmp;
unsigned long mask, submask;
unsigned long quot, rest;
if (offset >= size)
return size;
size -= result;
offset %= BITS_PER_LONG;
if (!offset)
goto aligned;
tmp = *(p++);
quot = (offset >> 3) << 3;
rest = offset & 0x7;
mask = ~(~0UL << quot);
submask = (unsigned char)~((unsigned char)(0xff << rest) >> rest);
submask <<= quot;
mask += submask;
tmp |= mask;
if (size < BITS_PER_LONG)
goto found_first;
if (~tmp)
goto found_middle;
size -= BITS_PER_LONG;
result += BITS_PER_LONG;
aligned:
while (size & ~(BITS_PER_LONG - 1)) {
tmp = *(p++);
if (~tmp)
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 + __reverse_ffz(tmp);
}
/*
* This function balances dirty node and dentry pages.
* In addition, it controls garbage collection.