diff options
Diffstat (limited to 'lib/find_bit.c')
| -rw-r--r-- | lib/find_bit.c | 49 |
1 files changed, 48 insertions, 1 deletions
diff --git a/lib/find_bit.c b/lib/find_bit.c index 32f99e9a670e..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 @@ -87,7 +88,7 @@ out: \ if (sz % BITS_PER_LONG) \ tmp = (FETCH) & BITMAP_LAST_WORD_MASK(sz); \ found: \ - sz = min(idx * BITS_PER_LONG + fns(tmp, nr), sz); \ + sz = idx * BITS_PER_LONG + fns(tmp, nr); \ out: \ sz; \ }) @@ -116,6 +117,29 @@ unsigned long _find_first_and_bit(const unsigned long *addr1, 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, + const unsigned long *addr2, + const unsigned long *addr3, + unsigned long size) +{ + return FIND_FIRST_BIT(addr1[idx] & addr2[idx] & addr3[idx], /* nop */, size); +} +EXPORT_SYMBOL(_find_first_and_and_bit); + #ifndef find_first_zero_bit /* * Find the first cleared bit in a memory region. @@ -268,3 +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); |