memcontrol04: Copy from kselftest

At first glance this test looks the same as memcontrol03. However
there are some significant changes which complicate combining the two.

At least up to kernel (5.17) there appears to be a bug causing low
memory events in F. There is presently no solution, so a known-bug tag
with a link to Michal's investigation has been included.

Signed-off-by: Richard Palethorpe <rpalethorpe@suse.com>
Reviewed-by: Li Wang <liwang@redhat.com>
Cc: Michal Koutný <mkoutny@suse.com>

runtest/controllers

@@ -20,6 +20,7 @@ memcg_control		memcg_control_test.sh
 memcontrol01 memcontrol01
 memcontrol02 memcontrol02
 memcontrol03 memcontrol03
+memcontrol04 memcontrol04
 
 cgroup_fj_function_debug cgroup_fj_function.sh debug
 cgroup_fj_function_cpuset cgroup_fj_function.sh cpuset

testcases/kernel/controllers/memcg/.gitignore

@@ -8,3 +8,4 @@
 memcontrol01
 memcontrol02
 memcontrol03
+memcontrol04

testcases/kernel/controllers/memcg/memcontrol04.c

@@ -0,0 +1,253 @@
+// SPDX-License-Identifier: GPL-2.0
+/*\
+ *
+ * [Description]
+ *
+ * Conversion of the forth kself test in cgroup/test_memcontrol.c.
+ *
+ * Original description:
+ * "First, this test creates the following hierarchy:
+ * A       memory.low = 50M,  memory.max = 200M
+ * A/B     memory.low = 50M,  memory.current = 50M
+ * A/B/C   memory.low = 75M,  memory.current = 50M
+ * A/B/D   memory.low = 25M,  memory.current = 50M
+ * A/B/E   memory.low = 500M, memory.current = 0
+ * A/B/F   memory.low = 0,    memory.current = 50M
+ *
+ * Usages are pagecache
+ * Then it creates A/G and creates a significant
+ * memory pressure in it.
+ *
+ * A/B    memory.current ~= 50M
+ * A/B/C  memory.current ~= 33M
+ * A/B/D  memory.current ~= 17M
+ * A/B/E  memory.current ~= 0
+ *
+ * After that it tries to allocate more than there is unprotected
+ * memory in A available, and checks that memory.low protects
+ * pagecache even in this case."
+ *
+ * The closest thing to memory.low on V1 is soft_limit_in_bytes which
+ * uses a different mechanism and has different semantics. So we only
+ * test on V2 like the selftest. We do test on more file systems, but
+ * not tempfs becaue it can't evict the page cache without swap. Also
+ * we avoid filesystems which allocate extra memory for buffer heads.
+ *
+ * The tolerances have been increased from the self tests.
+ */
+
+#define _GNU_SOURCE
+
+#include <inttypes.h>
+
+#include "memcontrol_common.h"
+
+#define TMPDIR "mntdir"
+
+static struct tst_cg_group *trunk_cg[3];
+static struct tst_cg_group *leaf_cg[4];
+static int fd = -1;
+
+enum checkpoints {
+	CHILD_IDLE
+};
+
+enum trunk_cg {
+	A,
+	B,
+	G
+};
+
+enum leaf_cg {
+	C,
+	D,
+	E,
+	F
+};
+
+static void cleanup_sub_groups(void)
+{
+	size_t i;
+
+	for (i = ARRAY_SIZE(leaf_cg); i > 0; i--) {
+		if (!leaf_cg[i - 1])
+			continue;
+
+		leaf_cg[i - 1] = tst_cg_group_rm(leaf_cg[i - 1]);
+	}
+
+	for (i = ARRAY_SIZE(trunk_cg); i > 0; i--) {
+		if (!trunk_cg[i - 1])
+			continue;
+
+		trunk_cg[i - 1] = tst_cg_group_rm(trunk_cg[i - 1]);
+	}
+}
+
+static void alloc_anon_in_child(const struct tst_cg_group *const cg,
+				const size_t size)
+{
+	const pid_t pid = SAFE_FORK();
+
+	if (pid) {
+		tst_reap_children();
+		return;
+	}
+
+	SAFE_CG_PRINTF(cg, "cgroup.procs", "%d", getpid());
+
+	tst_res(TINFO, "Child %d in %s: Allocating anon: %"PRIdPTR,
+		getpid(), tst_cg_group_name(cg), size);
+	alloc_anon(size);
+
+	exit(0);
+}
+
+static void alloc_pagecache_in_child(const struct tst_cg_group *const cg,
+				     const size_t size)
+{
+	const pid_t pid = SAFE_FORK();
+
+	if (pid) {
+		tst_reap_children();
+		return;
+	}
+
+	SAFE_CG_PRINTF(cg, "cgroup.procs", "%d", getpid());
+
+	tst_res(TINFO, "Child %d in %s: Allocating pagecache: %"PRIdPTR,
+		getpid(), tst_cg_group_name(cg), size);
+	alloc_pagecache(fd, size);
+
+	exit(0);
+}
+
+static void test_memcg_low(void)
+{
+	long c[4];
+	unsigned int i;
+
+	fd = SAFE_OPEN(TMPDIR"/tmpfile", O_RDWR | O_CREAT, 0600);
+	trunk_cg[A] = tst_cg_group_mk(tst_cg, "trunk_A");
+
+	SAFE_CG_SCANF(trunk_cg[A], "memory.low", "%ld", c);
+	if (c[0]) {
+		tst_brk(TCONF,
+			"memory.low already set to %ld on parent group", c[0]);
+	}
+
+	SAFE_CG_PRINT(trunk_cg[A], "cgroup.subtree_control", "+memory");
+
+	SAFE_CG_PRINT(trunk_cg[A], "memory.max", "200M");
+	SAFE_CG_PRINT(trunk_cg[A], "memory.swap.max", "0");
+
+	trunk_cg[B] = tst_cg_group_mk(trunk_cg[A], "trunk_B");
+
+	SAFE_CG_PRINT(trunk_cg[B], "cgroup.subtree_control", "+memory");
+
+	trunk_cg[G] = tst_cg_group_mk(trunk_cg[A], "trunk_G");
+
+	for (i = 0; i < ARRAY_SIZE(leaf_cg); i++) {
+		leaf_cg[i] = tst_cg_group_mk(trunk_cg[B],
+						 "leaf_%c", 'C' + i);
+
+		if (i == E)
+			continue;
+
+		alloc_pagecache_in_child(leaf_cg[i], MB(50));
+	}
+
+	SAFE_CG_PRINT(trunk_cg[A], "memory.low", "50M");
+	SAFE_CG_PRINT(trunk_cg[B], "memory.low", "50M");
+	SAFE_CG_PRINT(leaf_cg[C], "memory.low", "75M");
+	SAFE_CG_PRINT(leaf_cg[D], "memory.low", "25M");
+	SAFE_CG_PRINT(leaf_cg[E], "memory.low", "500M");
+	SAFE_CG_PRINT(leaf_cg[F], "memory.low", "0");
+
+	alloc_anon_in_child(trunk_cg[G], MB(148));
+
+	SAFE_CG_SCANF(trunk_cg[B], "memory.current", "%ld", c);
+	TST_EXP_EXPR(values_close(c[0], MB(50), 5),
+		     "(A/B memory.current=%ld) ~= %d", c[0], MB(50));
+
+	for (i = 0; i < ARRAY_SIZE(leaf_cg); i++)
+		SAFE_CG_SCANF(leaf_cg[i], "memory.current", "%ld", c + i);
+
+	TST_EXP_EXPR(values_close(c[0], MB(33), 20),
+		     "(A/B/C memory.current=%ld) ~= %d", c[C], MB(33));
+	TST_EXP_EXPR(values_close(c[1], MB(17), 20),
+		     "(A/B/D memory.current=%ld) ~= %d", c[D], MB(17));
+	TST_EXP_EXPR(values_close(c[2], 0, 1),
+		     "(A/B/E memory.current=%ld) ~= 0", c[E]);
+	tst_res(TINFO, "A/B/F memory.current=%ld", c[F]);
+
+	alloc_anon_in_child(trunk_cg[G], MB(166));
+
+	for (i = 0; i < ARRAY_SIZE(trunk_cg); i++) {
+		long low, oom;
+		const char id = "ABG"[i];
+
+		SAFE_CG_LINES_SCANF(trunk_cg[i], "memory.events",
+				    "low %ld", &low);
+		SAFE_CG_LINES_SCANF(trunk_cg[i], "memory.events",
+				    "oom %ld", &oom);
+
+		tst_res(TINFO, "%c: low events=%ld, oom events=%ld",
+			id, low, oom);
+	}
+
+	for (i = 0; i < ARRAY_SIZE(leaf_cg); i++) {
+		long low, oom;
+		const char id = 'C' + i;
+
+		SAFE_CG_LINES_SCANF(leaf_cg[i], "memory.events",
+				    "low %ld", &low);
+		SAFE_CG_LINES_SCANF(leaf_cg[i], "memory.events",
+				    "oom %ld", &oom);
+
+		TST_EXP_EXPR(oom == 0, "(%c oom events=%ld) == 0", id, oom);
+
+		if (i < E) {
+			TST_EXP_EXPR(low > 0,
+				     "(%c low events=%ld) > 0", id, low);
+		} else {
+			TST_EXP_EXPR(low == 0,
+				     "(%c low events=%ld) == 0", id, low);
+		}
+	}
+
+	cleanup_sub_groups();
+	SAFE_CLOSE(fd);
+	SAFE_UNLINK(TMPDIR"/tmpfile");
+}
+
+static void cleanup(void)
+{
+	cleanup_sub_groups();
+	if (fd > -1)
+		SAFE_CLOSE(fd);
+}
+
+static struct tst_test test = {
+	.cleanup = cleanup,
+	.test_all = test_memcg_low,
+	.mount_device = 1,
+	.dev_min_size = 256,
+	.mntpoint = TMPDIR,
+	.all_filesystems = 1,
+	.skip_filesystems = (const char *const[]){
+		"exfat", "vfat", "fuse", "ntfs", "tmpfs", NULL
+	},
+	.forks_child = 1,
+	.needs_root = 1,
+	.needs_checkpoints = 1,
+	.needs_cgroup_ver = TST_CG_V2,
+	.needs_cgroup_ctrls = (const char *const[]){ "memory", NULL },
+	.tags = (const struct tst_tag[]) {
+		{
+			"known-fail",
+			"Low events in F: https://bugzilla.suse.com/show_bug.cgi?id=1196298"
+		},
+		{}
+	},
+};