lib: Add strongly typed 64bit int_sqrt (47a36163) · Commits · 戴 / test

There is no option to perform 64bit integer sqrt on 32bit platform. Added stronger typed int_sqrt64 enables the 64bit calculations to be performed on 32bit platforms. Using same algorithm as int_sqrt() with strong typing provides enough precision also on 32bit platforms, but it sacrifices some performance. In case values are smaller than ULONG_MAX the standard int_sqrt is used for calculation to maximize the performance due to more native calculations. Signed-off-by:

Crt Mori <cmo@melexis.com> Acked-by:

Joe Perches <joe@perches.com> Signed-off-by:

Jonathan Cameron <Jonathan.Cameron@huawei.com>

include/linux/kernel.h

+9 −0

Original line number	Diff line number	Diff line
		@@ -479,6 +479,15 @@ extern int func_ptr_is_kernel_text(void *ptr);

		unsigned long int_sqrt(unsigned long);

		#if BITS_PER_LONG < 64
		u32 int_sqrt64(u64 x);
		#else
		static inline u32 int_sqrt64(u64 x)
		{
		return (u32)int_sqrt(x);
		}
		#endif

		extern void bust_spinlocks(int yes);
		extern int oops_in_progress; /* If set, an oops, panic(), BUG() or die() is in progress */
		extern int panic_timeout;

lib/int_sqrt.c

+30 −0

Original line number	Diff line number	Diff line
		@@ -38,3 +38,33 @@ unsigned long int_sqrt(unsigned long x)
		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) & ~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

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