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bitops: Add __ffs64 bitop

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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: Steven Whitehouse <swhiteho@redhat.com>
Reviewed-by: Christoph Lameter <cl@linux.com>
Reviewed-by: Willy Tarreau <w@1wt.eu>
This commit is contained in:
Steven Whitehouse 2009-04-23 08:48:15 +01:00
parent 0910697403
commit 952043ac12
1 changed files with 19 additions and 0 deletions
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19
include/linux/bitops.h
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@ -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