Merge branch 'akpm' (patches from Andrew)

Merge more updates from Andrew Morton:
 "190 patches.

  Subsystems affected by this patch series: mm (hugetlb, userfaultfd,
  vmscan, kconfig, proc, z3fold, zbud, ras, mempolicy, memblock,
  migration, thp, nommu, kconfig, madvise, memory-hotplug, zswap,
  zsmalloc, zram, cleanups, kfence, and hmm), procfs, sysctl, misc,
  core-kernel, lib, lz4, checkpatch, init, kprobes, nilfs2, hfs,
  signals, exec, kcov, selftests, compress/decompress, and ipc"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (190 commits)
  ipc/util.c: use binary search for max_idx
  ipc/sem.c: use READ_ONCE()/WRITE_ONCE() for use_global_lock
  ipc: use kmalloc for msg_queue and shmid_kernel
  ipc sem: use kvmalloc for sem_undo allocation
  lib/decompressors: remove set but not used variabled 'level'
  selftests/vm/pkeys: exercise x86 XSAVE init state
  selftests/vm/pkeys: refill shadow register after implicit kernel write
  selftests/vm/pkeys: handle negative sys_pkey_alloc() return code
  selftests/vm/pkeys: fix alloc_random_pkey() to make it really, really random
  kcov: add __no_sanitize_coverage to fix noinstr for all architectures
  exec: remove checks in __register_bimfmt()
  x86: signal: don't do sas_ss_reset() until we are certain that sigframe won't be abandoned
  hfsplus: report create_date to kstat.btime
  hfsplus: remove unnecessary oom message
  nilfs2: remove redundant continue statement in a while-loop
  kprobes: remove duplicated strong free_insn_page in x86 and s390
  init: print out unknown kernel parameters
  checkpatch: do not complain about positive return values starting with EPOLL
  checkpatch: improve the indented label test
  checkpatch: scripts/spdxcheck.py now requires python3
  ...

3 files changed, 68 insertions, 5 deletions

diff --git a/lib/math/Makefile b/lib/math/Makefile
index 7456edb864fc..bfac26ddfc22 100644
--- a/lib/math/Makefile
+++ b/lib/math/Makefile
@@ -6,3 +6,4 @@ obj-$(CONFIG_PRIME_NUMBERS)	+= prime_numbers.o
 obj-$(CONFIG_RATIONAL)		+= rational.o
 
 obj-$(CONFIG_TEST_DIV64)	+= test_div64.o
+obj-$(CONFIG_RATIONAL_KUNIT_TEST) += rational-test.o
diff --git a/lib/math/rational-test.c b/lib/math/rational-test.c
new file mode 100644
index 000000000000..01611ddff420
--- /dev/null
+++ b/lib/math/rational-test.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <kunit/test.h>
+
+#include <linux/rational.h>
+
+struct rational_test_param {
+	unsigned long num, den;
+	unsigned long max_num, max_den;
+	unsigned long exp_num, exp_den;
+
+	const char *name;
+};
+
+static const struct rational_test_param test_parameters[] = {
+	{ 1230,	10,	100, 20,	100, 1,    "Exceeds bounds, semi-convergent term > 1/2 last term" },
+	{ 34567,100, 	120, 20,	120, 1,    "Exceeds bounds, semi-convergent term < 1/2 last term" },
+	{ 1, 30,	100, 10,	0, 1,	   "Closest to zero" },
+	{ 1, 19,	100, 10,	1, 10,     "Closest to smallest non-zero" },
+	{ 27,32,	16, 16,		11, 13,    "Use convergent" },
+	{ 1155, 7735,	255, 255,	33, 221,   "Exact answer" },
+	{ 87, 32,	70, 32,		68, 25,    "Semiconvergent, numerator limit" },
+	{ 14533, 4626,	15000, 2400,	7433, 2366, "Semiconvergent, denominator limit" },
+};
+
+static void get_desc(const struct rational_test_param *param, char *desc)
+{
+	strscpy(desc, param->name, KUNIT_PARAM_DESC_SIZE);
+}
+
+/* Creates function rational_gen_params */
+KUNIT_ARRAY_PARAM(rational, test_parameters, get_desc);
+
+static void rational_test(struct kunit *test)
+{
+	const struct rational_test_param *param = (const struct rational_test_param *)test->param_value;
+	unsigned long n = 0, d = 0;
+
+	rational_best_approximation(param->num, param->den, param->max_num, param->max_den, &n, &d);
+	KUNIT_EXPECT_EQ(test, n, param->exp_num);
+	KUNIT_EXPECT_EQ(test, d, param->exp_den);
+}
+
+static struct kunit_case rational_test_cases[] = {
+	KUNIT_CASE_PARAM(rational_test, rational_gen_params),
+	{}
+};
+
+static struct kunit_suite rational_test_suite = {
+	.name = "rational",
+	.test_cases = rational_test_cases,
+};
+
+kunit_test_suites(&rational_test_suite);
+
+MODULE_LICENSE("GPL v2");
diff --git a/lib/math/rational.c b/lib/math/rational.c
index 9781d521963d..c0ab51d8fbb9 100644
--- a/lib/math/rational.c
+++ b/lib/math/rational.c
@@ -12,6 +12,7 @@
 #include <linux/compiler.h>
 #include <linux/export.h>
 #include <linux/minmax.h>
+#include <linux/limits.h>
 
 /*
  * calculate best rational approximation for a given fraction
@@ -78,13 +79,18 @@ void rational_best_approximation(
 		 * found below as 't'.
 		 */
 		if ((n2 > max_numerator) || (d2 > max_denominator)) {
-			unsigned long t = min((max_numerator - n0) / n1,
-					      (max_denominator - d0) / d1);
+			unsigned long t = ULONG_MAX;
 
-			/* This tests if the semi-convergent is closer
-			 * than the previous convergent.
+			if (d1)
+				t = (max_denominator - d0) / d1;
+			if (n1)
+				t = min(t, (max_numerator - n0) / n1);
+
+			/* This tests if the semi-convergent is closer than the previous
+			 * convergent.  If d1 is zero there is no previous convergent as this
+			 * is the 1st iteration, so always choose the semi-convergent.
 			 */
-			if (2u * t > a || (2u * t == a && d0 * dp > d1 * d)) {
+			if (!d1 || 2u * t > a || (2u * t == a && d0 * dp > d1 * d)) {
 				n1 = n0 + t * n1;
 				d1 = d0 + t * d1;
 			}