[PATCH] sqrt() fixes

It turns out that the int_sqrt() function in oom_kill.c gets it wrong.

But fb_sqrt() in fbmon.c gets its math right.  Move that function into
lib/int_sqrt.c, and consolidate.

(oom_kill.c fix from Thomas Schlichter <schlicht@uni-mannheim.de>)

2 files changed, 33 insertions, 1 deletions

diff --git a/lib/Makefile b/lib/Makefile
index 3bc9013c4b9738..2fd41ecbb127d2 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -5,7 +5,7 @@
 
 lib-y := errno.o ctype.o string.o vsprintf.o cmdline.o \
 	 bust_spinlocks.o rbtree.o radix-tree.o dump_stack.o \
-	 kobject.o idr.o div64.o parser.o
+	 kobject.o idr.o div64.o parser.o int_sqrt.o
 
 lib-$(CONFIG_RWSEM_GENERIC_SPINLOCK) += rwsem-spinlock.o
 lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o
diff --git a/lib/int_sqrt.c b/lib/int_sqrt.c
new file mode 100644
index 00000000000000..a5d2cdc5684cfd
--- /dev/null
+++ b/lib/int_sqrt.c
@@ -0,0 +1,32 @@
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+/**
+ * int_sqrt - rough approximation to sqrt
+ * @x: integer of which to calculate the sqrt
+ *
+ * A very rough approximation to the sqrt() function.
+ */
+unsigned long int_sqrt(unsigned long x)
+{
+	unsigned long op, res, one;
+
+	op = x;
+	res = 0;
+
+	one = 1 << 30;
+	while (one > op)
+		one >>= 2;
+
+	while (one != 0) {
+		if (op >= res + one) {
+			op = op - (res + one);
+			res = res +  2 * one;
+		}
+		res /= 2;
+		one /= 4;
+	}
+	return res;
+}
+EXPORT_SYMBOL(int_sqrt);