text: // 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
  