From 952043ac12a117d8e94bddd9088338d7ad20ca7d Mon Sep 17 00:00:00 2001 From: Steven Whitehouse Date: Thu, 23 Apr 2009 08:48:15 +0100 Subject: 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: Steven Whitehouse Reviewed-by: Christoph Lameter Reviewed-by: Willy Tarreau --- include/linux/bitops.h | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) (limited to 'include') diff --git a/include/linux/bitops.h b/include/linux/bitops.h index 61829139795a..c05a29cb9bb2 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -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 -- cgit v1.2.3-59-g8ed1b