diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/flex_array.c | 7 | ||||
| -rw-r--r-- | lib/reciprocal_div.c | 24 |
2 files changed, 26 insertions, 5 deletions
diff --git a/lib/flex_array.c b/lib/flex_array.c index 6948a6692fc4..2eed22fa507c 100644 --- a/lib/flex_array.c +++ b/lib/flex_array.c @@ -90,8 +90,8 @@ struct flex_array *flex_array_alloc(int element_size, unsigned int total, { struct flex_array *ret; int elems_per_part = 0; - int reciprocal_elems = 0; int max_size = 0; + struct reciprocal_value reciprocal_elems = { 0 }; if (element_size) { elems_per_part = FLEX_ARRAY_ELEMENTS_PER_PART(element_size); @@ -119,6 +119,11 @@ EXPORT_SYMBOL(flex_array_alloc); static int fa_element_to_part_nr(struct flex_array *fa, unsigned int element_nr) { + /* + * if element_size == 0 we don't get here, so we never touch + * the zeroed fa->reciprocal_elems, which would yield invalid + * results + */ return reciprocal_divide(element_nr, fa->reciprocal_elems); } diff --git a/lib/reciprocal_div.c b/lib/reciprocal_div.c index 75510e94f7d0..464152410c51 100644 --- a/lib/reciprocal_div.c +++ b/lib/reciprocal_div.c @@ -1,11 +1,27 @@ +#include <linux/kernel.h> #include <asm/div64.h> #include <linux/reciprocal_div.h> #include <linux/export.h> -u32 reciprocal_value(u32 k) +/* + * For a description of the algorithm please have a look at + * include/linux/reciprocal_div.h + */ + +struct reciprocal_value reciprocal_value(u32 d) { - u64 val = (1LL << 32) + (k - 1); - do_div(val, k); - return (u32)val; + struct reciprocal_value R; + u64 m; + int l; + + l = fls(d - 1); + m = ((1ULL << 32) * ((1ULL << l) - d)); + do_div(m, d); + ++m; + R.m = (u32)m; + R.sh1 = min(l, 1); + R.sh2 = max(l - 1, 0); + + return R; } EXPORT_SYMBOL(reciprocal_value); |