diff options
author | Kent Overstreet <kent.overstreet@linux.dev> | 2022-10-12 16:29:56 -0400 |
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committer | Kent Overstreet <kent.overstreet@linux.dev> | 2022-10-15 01:04:30 -0400 |
commit | e0a51ccce8533a91c7cc0cd0adc5662697c9bcfa (patch) | |
tree | 91408761ffbd7da783886c94a354d3b642e10587 /linux/int_sqrt.c | |
parent | 3165f53b28b87b3c46c95763bae5e40a29166e2e (diff) |
Update bcachefs sources to 3e93567c51 bcachefs: Switch to local_clock() for fastpath time source
Diffstat (limited to 'linux/int_sqrt.c')
-rw-r--r-- | linux/int_sqrt.c | 71 |
1 files changed, 71 insertions, 0 deletions
diff --git a/linux/int_sqrt.c b/linux/int_sqrt.c new file mode 100644 index 00000000..a8170bb9 --- /dev/null +++ b/linux/int_sqrt.c @@ -0,0 +1,71 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2013 Davidlohr Bueso <davidlohr.bueso@hp.com> + * + * Based on the shift-and-subtract algorithm for computing integer + * square root from Guy L. Steele. + */ + +#include <linux/export.h> +#include <linux/bitops.h> +#include <linux/limits.h> +#include <linux/math.h> + +/** + * int_sqrt - computes the integer square root + * @x: integer of which to calculate the sqrt + * + * Computes: floor(sqrt(x)) + */ +unsigned long int_sqrt(unsigned long x) +{ + unsigned long b, m, y = 0; + + if (x <= 1) + return x; + + m = 1UL << (__fls(x) & ~1UL); + while (m != 0) { + b = y + m; + y >>= 1; + + if (x >= b) { + x -= b; + y += m; + } + m >>= 2; + } + + return y; +} +EXPORT_SYMBOL(int_sqrt); + +#if BITS_PER_LONG < 64 +/** + * int_sqrt64 - strongly typed int_sqrt function when minimum 64 bit input + * is expected. + * @x: 64bit integer of which to calculate the sqrt + */ +u32 int_sqrt64(u64 x) +{ + u64 b, m, y = 0; + + if (x <= ULONG_MAX) + return int_sqrt((unsigned long) x); + + m = 1ULL << ((fls64(x) - 1) & ~1ULL); + while (m != 0) { + b = y + m; + y >>= 1; + + if (x >= b) { + x -= b; + y += m; + } + m >>= 2; + } + + return y; +} +EXPORT_SYMBOL(int_sqrt64); +#endif |