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author | Steven Whitehouse <swhiteho@redhat.com> | 2009-04-23 08:48:15 +0100 |
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committer | Steven Whitehouse <swhiteho@redhat.com> | 2009-04-23 10:06:35 +0100 |
commit | 952043ac12a117d8e94bddd9088338d7ad20ca7d (patch) | |
tree | 3ad716873d90392fbf1888084af9be7e5e242e1f /include/linux/bitops.h | |
parent | 091069740304c979f957ceacec39c461d0192158 (diff) | |
download | kernel_samsung_espresso10-952043ac12a117d8e94bddd9088338d7ad20ca7d.zip kernel_samsung_espresso10-952043ac12a117d8e94bddd9088338d7ad20ca7d.tar.gz kernel_samsung_espresso10-952043ac12a117d8e94bddd9088338d7ad20ca7d.tar.bz2 |
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 <swhiteho@redhat.com>
Reviewed-by: Christoph Lameter <cl@linux.com>
Reviewed-by: Willy Tarreau <w@1wt.eu>
Diffstat (limited to 'include/linux/bitops.h')
-rw-r--r-- | include/linux/bitops.h | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/include/linux/bitops.h b/include/linux/bitops.h index 6182913..c05a29c 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 |