diff options
Diffstat (limited to 'lib/find_bit.c')
| -rw-r--r-- | lib/find_bit.c | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/lib/find_bit.c b/lib/find_bit.c index 0836bb3d76c5..d4b5a29e3e72 100644 --- a/lib/find_bit.c +++ b/lib/find_bit.c @@ -18,6 +18,7 @@ #include <linux/math.h> #include <linux/minmax.h> #include <linux/swab.h> +#include <linux/random.h> /* * Common helper for find_bit() function family @@ -117,6 +118,17 @@ EXPORT_SYMBOL(_find_first_and_bit); #endif /* + * Find the first bit set in 1st memory region and unset in 2nd. + */ +unsigned long _find_first_andnot_bit(const unsigned long *addr1, + const unsigned long *addr2, + unsigned long size) +{ + return FIND_FIRST_BIT(addr1[idx] & ~addr2[idx], /* nop */, size); +} +EXPORT_SYMBOL(_find_first_andnot_bit); + +/* * Find the first set bit in three memory regions. */ unsigned long _find_first_and_and_bit(const unsigned long *addr1, @@ -280,3 +292,26 @@ EXPORT_SYMBOL(_find_next_bit_le); #endif #endif /* __BIG_ENDIAN */ + +/** + * find_random_bit - find a set bit at random position + * @addr: The address to base the search on + * @size: The bitmap size in bits + * + * Returns: a position of a random set bit; >= @size otherwise + */ +unsigned long find_random_bit(const unsigned long *addr, unsigned long size) +{ + int w = bitmap_weight(addr, size); + + switch (w) { + case 0: + return size; + case 1: + /* Performance trick for single-bit bitmaps */ + return find_first_bit(addr, size); + default: + return find_nth_bit(addr, size, get_random_u32_below(w)); + } +} +EXPORT_SYMBOL(find_random_bit); |