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Commit 952043ac authored by Steven Whitehouse's avatar Steven Whitehouse
Browse files

bitops: Add __ffs64 bitop 



Finds the first set bit in a 64 bit word. This is required in order
to fix a bug in GFS2, but I think it should be a generic function
in case of future users.

Signed-off-by: default avatarSteven Whitehouse <swhiteho@redhat.com>
Reviewed-by: default avatarChristoph Lameter <cl@linux.com>
Reviewed-by: default avatarWilly Tarreau <w@1wt.eu>
parent 09106974

include/linux/bitops.h

+19 −0
Original line number Diff line number Diff line
@@ -112,6 +112,25 @@ static inline unsigned fls_long(unsigned long l) 
	return fls64(l);

}



/**

 * __ffs64 - find first set bit in a 64 bit word

 * @word: The 64 bit word

 *

 * On 64 bit arches this is a synomyn for __ffs

 * The result is not defined if no bits are set, so check that @word

 * is non-zero before calling this.

 */

static inline unsigned long __ffs64(u64 word)

{

#if BITS_PER_LONG == 32

	if (((u32)word) == 0UL)

		return __ffs((u32)(word >> 32)) + 32;

#elif BITS_PER_LONG != 64

#error BITS_PER_LONG not 32 or 64

#endif

	return __ffs((unsigned long)word);

}



#ifdef __KERNEL__

#ifdef CONFIG_GENERIC_FIND_FIRST_BIT