Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 9a7f143a authored by Changman Lee's avatar Changman Lee Committed by Jaegeuk Kim
Browse files

f2fs: introduce __find_rev_next(_zero)_bit 



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: default avatarChangman Lee <cm224.lee@samsung.com>
[Jaegeuk Kim: change the function names]
Signed-off-by: default avatarJaegeuk Kim <jaegeuk.kim@samsung.com>
parent 413541dd

fs/f2fs/segment.c

+148 −0
Original line number Diff line number Diff line
@@ -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.