tools/testing/selftests/cgroup/test_zswap.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 #define _GNU_SOURCE

 #include <linux/limits.h>
 #include <unistd.h>
 #include <stdio.h>
 #include <signal.h>
 #include <sys/sysinfo.h>
 #include <string.h>
 #include <sys/wait.h>
 #include <sys/mman.h>

 #include "../kselftest.h"
 #include "cgroup_util.h"

 static int read_int(const char *path, size_t *value)
 {
 	FILE *file;
 	int ret = 0;

 	file = fopen(path, "r");
 	if (!file)
 		return -1;
 	if (fscanf(file, "%ld", value) != 1)
 		ret = -1;
 	fclose(file);
 	return ret;
 }

 static int set_min_free_kb(size_t value)
 {
 	FILE *file;
 	int ret;

 	file = fopen("/proc/sys/vm/min_free_kbytes", "w");
 	if (!file)
 		return -1;
 	ret = fprintf(file, "%ld\n", value);
 	fclose(file);
 	return ret;
 }

 static int read_min_free_kb(size_t *value)
 {
 	return read_int("/proc/sys/vm/min_free_kbytes", value);
 }

 static int get_zswap_stored_pages(size_t *value)
 {
 	return read_int("/sys/kernel/debug/zswap/stored_pages", value);
 }

 static int get_cg_wb_count(const char *cg)
 {
 	return cg_read_key_long(cg, "memory.stat", "zswpwb");
 }

 static long get_zswpout(const char *cgroup)
 {
 	return cg_read_key_long(cgroup, "memory.stat", "zswpout ");
 }

 static int allocate_and_read_bytes(const char *cgroup, void *arg)
 {
 	size_t size = (size_t)arg;
 	char *mem = (char *)malloc(size);
 	int ret = 0;

 	if (!mem)
 		return -1;
 	for (int i = 0; i < size; i += 4095)
 		mem[i] = 'a';

 	/* Go through the allocated memory to (z)swap in and out pages */
 	for (int i = 0; i < size; i += 4095) {
 		if (mem[i] != 'a')
 			ret = -1;
 	}

 	free(mem);
 	return ret;
 }

 static int allocate_bytes(const char *cgroup, void *arg)
 {
 	size_t size = (size_t)arg;
 	char *mem = (char *)malloc(size);

 	if (!mem)
 		return -1;
 	for (int i = 0; i < size; i += 4095)
 		mem[i] = 'a';
 	free(mem);
 	return 0;
 }

 static char *setup_test_group_1M(const char *root, const char *name)
 {
 	char *group_name = cg_name(root, name);

 	if (!group_name)
 		return NULL;
 	if (cg_create(group_name))
 		goto fail;
 	if (cg_write(group_name, "memory.max", "1M")) {
 		cg_destroy(group_name);
 		goto fail;
 	}
 	return group_name;
 fail:
 	free(group_name);
 	return NULL;
 }

 /*
  * Sanity test to check that pages are written into zswap.
  */
 static int test_zswap_usage(const char *root)
 {
 	long zswpout_before, zswpout_after;
 	int ret = KSFT_FAIL;
 	char *test_group;

 	test_group = cg_name(root, "no_shrink_test");
 	if (!test_group)
 		goto out;
 	if (cg_create(test_group))
 		goto out;
 	if (cg_write(test_group, "memory.max", "1M"))
 		goto out;

 	zswpout_before = get_zswpout(test_group);
 	if (zswpout_before < 0) {
 		ksft_print_msg("Failed to get zswpout\n");
 		goto out;
 	}

 	/* Allocate more than memory.max to push memory into zswap */
 	if (cg_run(test_group, allocate_bytes, (void *)MB(4)))
 		goto out;

 	/* Verify that pages come into zswap */
 	zswpout_after = get_zswpout(test_group);
 	if (zswpout_after <= zswpout_before) {
 		ksft_print_msg("zswpout does not increase after test program\n");
 		goto out;
 	}
 	ret = KSFT_PASS;

 out:
 	cg_destroy(test_group);
 	free(test_group);
 	return ret;
 }

 /*
  * Check that when memory.zswap.max = 0, no pages can go to the zswap pool for
  * the cgroup.
  */
 static int test_swapin_nozswap(const char *root)
 {
 	int ret = KSFT_FAIL;
 	char *test_group;
 	long swap_peak, zswpout;

 	test_group = cg_name(root, "no_zswap_test");
 	if (!test_group)
 		goto out;
 	if (cg_create(test_group))
 		goto out;
 	if (cg_write(test_group, "memory.max", "8M"))
 		goto out;
 	if (cg_write(test_group, "memory.zswap.max", "0"))
 		goto out;

 	/* Allocate and read more than memory.max to trigger swapin */
 	if (cg_run(test_group, allocate_and_read_bytes, (void *)MB(32)))
 		goto out;

 	/* Verify that pages are swapped out, but no zswap happened */
 	swap_peak = cg_read_long(test_group, "memory.swap.peak");
 	if (swap_peak < 0) {
 		ksft_print_msg("failed to get cgroup's swap_peak\n");
 		goto out;
 	}

 	if (swap_peak < MB(24)) {
 		ksft_print_msg("at least 24MB of memory should be swapped out\n");
 		goto out;
 	}

 	zswpout = get_zswpout(test_group);
 	if (zswpout < 0) {
 		ksft_print_msg("failed to get zswpout\n");
 		goto out;
 	}

 	if (zswpout > 0) {
 		ksft_print_msg("zswapout > 0 when memory.zswap.max = 0\n");
 		goto out;
 	}

 	ret = KSFT_PASS;

 out:
 	cg_destroy(test_group);
 	free(test_group);
 	return ret;
 }

 /* Simple test to verify the (z)swapin code paths */
 static int test_zswapin(const char *root)
 {
 	int ret = KSFT_FAIL;
 	char *test_group;
 	long zswpin;

 	test_group = cg_name(root, "zswapin_test");
 	if (!test_group)
 		goto out;
 	if (cg_create(test_group))
 		goto out;
 	if (cg_write(test_group, "memory.max", "8M"))
 		goto out;
 	if (cg_write(test_group, "memory.zswap.max", "max"))
 		goto out;

 	/* Allocate and read more than memory.max to trigger (z)swap in */
 	if (cg_run(test_group, allocate_and_read_bytes, (void *)MB(32)))
 		goto out;

 	zswpin = cg_read_key_long(test_group, "memory.stat", "zswpin ");
 	if (zswpin < 0) {
 		ksft_print_msg("failed to get zswpin\n");
 		goto out;
 	}

 	if (zswpin < MB(24) / PAGE_SIZE) {
 		ksft_print_msg("at least 24MB should be brought back from zswap\n");
 		goto out;
 	}

 	ret = KSFT_PASS;

 out:
 	cg_destroy(test_group);
 	free(test_group);
 	return ret;
 }

 /*
  * When trying to store a memcg page in zswap, if the memcg hits its memory
  * limit in zswap, writeback should affect only the zswapped pages of that
  * memcg.
  */
 static int test_no_invasive_cgroup_shrink(const char *root)
 {
 	int ret = KSFT_FAIL;
 	size_t control_allocation_size = MB(10);
 	char *control_allocation, *wb_group = NULL, *control_group = NULL;

 	wb_group = setup_test_group_1M(root, "per_memcg_wb_test1");
 	if (!wb_group)
 		return KSFT_FAIL;
 	if (cg_write(wb_group, "memory.zswap.max", "10K"))
 		goto out;
 	control_group = setup_test_group_1M(root, "per_memcg_wb_test2");
 	if (!control_group)
 		goto out;

 	/* Push some test_group2 memory into zswap */
 	if (cg_enter_current(control_group))
 		goto out;
 	control_allocation = malloc(control_allocation_size);
 	for (int i = 0; i < control_allocation_size; i += 4095)
 		control_allocation[i] = 'a';
 	if (cg_read_key_long(control_group, "memory.stat", "zswapped") < 1)
 		goto out;

 	/* Allocate 10x memory.max to push wb_group memory into zswap and trigger wb */
 	if (cg_run(wb_group, allocate_bytes, (void *)MB(10)))
 		goto out;

 	/* Verify that only zswapped memory from gwb_group has been written back */
 	if (get_cg_wb_count(wb_group) > 0 && get_cg_wb_count(control_group) == 0)
 		ret = KSFT_PASS;
 out:
 	cg_enter_current(root);
 	if (control_group) {
 		cg_destroy(control_group);
 		free(control_group);
 	}
 	cg_destroy(wb_group);
 	free(wb_group);
 	if (control_allocation)
 		free(control_allocation);
 	return ret;
 }

 struct no_kmem_bypass_child_args {
 	size_t target_alloc_bytes;
 	size_t child_allocated;
 };

 static int no_kmem_bypass_child(const char *cgroup, void *arg)
 {
 	struct no_kmem_bypass_child_args *values = arg;
 	void *allocation;

 	allocation = malloc(values->target_alloc_bytes);
 	if (!allocation) {
 		values->child_allocated = true;
 		return -1;
 	}
 	for (long i = 0; i < values->target_alloc_bytes; i += 4095)
 		((char *)allocation)[i] = 'a';
 	values->child_allocated = true;
 	pause();
 	free(allocation);
 	return 0;
 }

 /*
  * When pages owned by a memcg are pushed to zswap by kswapd, they should be
  * charged to that cgroup. This wasn't the case before commit
  * cd08d80ecdac("mm: correctly charge compressed memory to its memcg").
  *
  * The test first allocates memory in a memcg, then raises min_free_kbytes to
  * a very high value so that the allocation falls below low wm, then makes
  * another allocation to trigger kswapd that should push the memcg-owned pages
  * to zswap and verifies that the zswap pages are correctly charged.
  *
  * To be run on a VM with at most 4G of memory.
  */
 static int test_no_kmem_bypass(const char *root)
 {
 	size_t min_free_kb_high, min_free_kb_low, min_free_kb_original;
 	struct no_kmem_bypass_child_args *values;
 	size_t trigger_allocation_size;
 	int wait_child_iteration = 0;
 	long stored_pages_threshold;
 	struct sysinfo sys_info;
 	int ret = KSFT_FAIL;
 	int child_status;
 	char *test_group;
 	pid_t child_pid;

 	/* Read sys info and compute test values accordingly */
 	if (sysinfo(&sys_info) != 0)
 		return KSFT_FAIL;
 	if (sys_info.totalram > 5000000000)
 		return KSFT_SKIP;
 	values = mmap(0, sizeof(struct no_kmem_bypass_child_args), PROT_READ |
 			PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0);
 	if (values == MAP_FAILED)
 		return KSFT_FAIL;
 	if (read_min_free_kb(&min_free_kb_original))
 		return KSFT_FAIL;
 	min_free_kb_high = sys_info.totalram / 2000;
 	min_free_kb_low = sys_info.totalram / 500000;
 	values->target_alloc_bytes = (sys_info.totalram - min_free_kb_high * 1000) +
 		sys_info.totalram * 5 / 100;
 	stored_pages_threshold = sys_info.totalram / 5 / 4096;
 	trigger_allocation_size = sys_info.totalram / 20;

 	/* Set up test memcg */
 	if (cg_write(root, "cgroup.subtree_control", "+memory"))
 		goto out;
 	test_group = cg_name(root, "kmem_bypass_test");
 	if (!test_group)
 		goto out;

 	/* Spawn memcg child and wait for it to allocate */
 	set_min_free_kb(min_free_kb_low);
 	if (cg_create(test_group))
 		goto out;
 	values->child_allocated = false;
 	child_pid = cg_run_nowait(test_group, no_kmem_bypass_child, values);
 	if (child_pid < 0)
 		goto out;
 	while (!values->child_allocated && wait_child_iteration++ < 10000)
 		usleep(1000);

 	/* Try to wakeup kswapd and let it push child memory to zswap */
 	set_min_free_kb(min_free_kb_high);
 	for (int i = 0; i < 20; i++) {
 		size_t stored_pages;
 		char *trigger_allocation = malloc(trigger_allocation_size);

 		if (!trigger_allocation)
 			break;
 		for (int i = 0; i < trigger_allocation_size; i += 4095)
 			trigger_allocation[i] = 'b';
 		usleep(100000);
 		free(trigger_allocation);
 		if (get_zswap_stored_pages(&stored_pages))
 			break;
 		if (stored_pages < 0)
 			break;
 		/* If memory was pushed to zswap, verify it belongs to memcg */
 		if (stored_pages > stored_pages_threshold) {
 			int zswapped = cg_read_key_long(test_group, "memory.stat", "zswapped ");
 			int delta = stored_pages * 4096 - zswapped;
 			int result_ok = delta < stored_pages * 4096 / 4;

 			ret = result_ok ? KSFT_PASS : KSFT_FAIL;
 			break;
 		}
 	}

 	kill(child_pid, SIGTERM);
 	waitpid(child_pid, &child_status, 0);
 out:
 	set_min_free_kb(min_free_kb_original);
 	cg_destroy(test_group);
 	free(test_group);
 	return ret;
 }

 #define T(x) { x, #x }
 struct zswap_test {
 	int (*fn)(const char *root);
 	const char *name;
 } tests[] = {
 	T(test_zswap_usage),
 	T(test_swapin_nozswap),
 	T(test_zswapin),
 	T(test_no_kmem_bypass),
 	T(test_no_invasive_cgroup_shrink),
 };
 #undef T

 static bool zswap_configured(void)
 {
 	return access("/sys/module/zswap", F_OK) == 0;
 }

 int main(int argc, char **argv)
 {
 	char root[PATH_MAX];
 	int i, ret = EXIT_SUCCESS;

 	if (cg_find_unified_root(root, sizeof(root)))
 		ksft_exit_skip("cgroup v2 isn't mounted\n");

 	if (!zswap_configured())
 		ksft_exit_skip("zswap isn't configured\n");

 	/*
 	 * Check that memory controller is available:
 	 * memory is listed in cgroup.controllers
 	 */
 	if (cg_read_strstr(root, "cgroup.controllers", "memory"))
 		ksft_exit_skip("memory controller isn't available\n");

 	if (cg_read_strstr(root, "cgroup.subtree_control", "memory"))
 		if (cg_write(root, "cgroup.subtree_control", "+memory"))
 			ksft_exit_skip("Failed to set memory controller\n");

 	for (i = 0; i < ARRAY_SIZE(tests); i++) {
 		switch (tests[i].fn(root)) {
 		case KSFT_PASS:
 			ksft_test_result_pass("%s\n", tests[i].name);
 			break;
 		case KSFT_SKIP:
 			ksft_test_result_skip("%s\n", tests[i].name);
 			break;
 		default:
 			ret = EXIT_FAILURE;
 			ksft_test_result_fail("%s\n", tests[i].name);
 			break;
 		}
 	}

 	return ret;
 }
	// SPDX-License-Identifier: GPL-2.0
	#define _GNU_SOURCE

	#include <linux/limits.h>
	#include <unistd.h>
	#include <stdio.h>
	#include <signal.h>
	#include <sys/sysinfo.h>
	#include <string.h>
	#include <sys/wait.h>
	#include <sys/mman.h>

	#include "../kselftest.h"
	#include "cgroup_util.h"

	static int read_int(const char path, size_t value)
	{
	FILE *file;
	int ret = 0;

	file = fopen(path, "r");
	if (!file)
	return -1;
	if (fscanf(file, "%ld", value) != 1)
	ret = -1;
	fclose(file);
	return ret;
	}

	static int set_min_free_kb(size_t value)
	{
	FILE *file;
	int ret;

	file = fopen("/proc/sys/vm/min_free_kbytes", "w");
	if (!file)
	return -1;
	ret = fprintf(file, "%ld\n", value);
	fclose(file);
	return ret;
	}

	static int read_min_free_kb(size_t *value)
	{
	return read_int("/proc/sys/vm/min_free_kbytes", value);
	}

	static int get_zswap_stored_pages(size_t *value)
	{
	return read_int("/sys/kernel/debug/zswap/stored_pages", value);
	}

	static int get_cg_wb_count(const char *cg)
	{
	return cg_read_key_long(cg, "memory.stat", "zswpwb");
	}

	static long get_zswpout(const char *cgroup)
	{
	return cg_read_key_long(cgroup, "memory.stat", "zswpout ");
	}

	static int allocate_and_read_bytes(const char cgroup, void arg)
	{
	size_t size = (size_t)arg;
	char mem = (char )malloc(size);
	int ret = 0;

	if (!mem)
	return -1;
	for (int i = 0; i < size; i += 4095)
	mem[i] = 'a';

	/* Go through the allocated memory to (z)swap in and out pages */
	for (int i = 0; i < size; i += 4095) {
	if (mem[i] != 'a')
	ret = -1;
	}

	free(mem);
	return ret;
	}

	static int allocate_bytes(const char cgroup, void arg)
	{
	size_t size = (size_t)arg;
	char mem = (char )malloc(size);

	if (!mem)
	return -1;
	for (int i = 0; i < size; i += 4095)
	mem[i] = 'a';
	free(mem);
	return 0;
	}

	static char setup_test_group_1M(const char root, const char *name)
	{
	char *group_name = cg_name(root, name);

	if (!group_name)
	return NULL;
	if (cg_create(group_name))
	goto fail;
	if (cg_write(group_name, "memory.max", "1M")) {
	cg_destroy(group_name);
	goto fail;
	}
	return group_name;
	fail:
	free(group_name);
	return NULL;
	}

	/*
	* Sanity test to check that pages are written into zswap.
	*/
	static int test_zswap_usage(const char *root)
	{
	long zswpout_before, zswpout_after;
	int ret = KSFT_FAIL;
	char *test_group;

	test_group = cg_name(root, "no_shrink_test");
	if (!test_group)
	goto out;
	if (cg_create(test_group))
	goto out;
	if (cg_write(test_group, "memory.max", "1M"))
	goto out;

	zswpout_before = get_zswpout(test_group);
	if (zswpout_before < 0) {
	ksft_print_msg("Failed to get zswpout\n");
	goto out;
	}

	/* Allocate more than memory.max to push memory into zswap */
	if (cg_run(test_group, allocate_bytes, (void *)MB(4)))
	goto out;

	/* Verify that pages come into zswap */
	zswpout_after = get_zswpout(test_group);
	if (zswpout_after <= zswpout_before) {
	ksft_print_msg("zswpout does not increase after test program\n");
	goto out;
	}
	ret = KSFT_PASS;

	out:
	cg_destroy(test_group);
	free(test_group);
	return ret;
	}

	/*
	* Check that when memory.zswap.max = 0, no pages can go to the zswap pool for
	* the cgroup.
	*/
	static int test_swapin_nozswap(const char *root)
	{
	int ret = KSFT_FAIL;
	char *test_group;
	long swap_peak, zswpout;

	test_group = cg_name(root, "no_zswap_test");
	if (!test_group)
	goto out;
	if (cg_create(test_group))
	goto out;
	if (cg_write(test_group, "memory.max", "8M"))
	goto out;
	if (cg_write(test_group, "memory.zswap.max", "0"))
	goto out;

	/* Allocate and read more than memory.max to trigger swapin */
	if (cg_run(test_group, allocate_and_read_bytes, (void *)MB(32)))
	goto out;

	/* Verify that pages are swapped out, but no zswap happened */
	swap_peak = cg_read_long(test_group, "memory.swap.peak");
	if (swap_peak < 0) {
	ksft_print_msg("failed to get cgroup's swap_peak\n");
	goto out;
	}

	if (swap_peak < MB(24)) {
	ksft_print_msg("at least 24MB of memory should be swapped out\n");
	goto out;
	}

	zswpout = get_zswpout(test_group);
	if (zswpout < 0) {
	ksft_print_msg("failed to get zswpout\n");
	goto out;
	}

	if (zswpout > 0) {
	ksft_print_msg("zswapout > 0 when memory.zswap.max = 0\n");
	goto out;
	}

	ret = KSFT_PASS;

	out:
	cg_destroy(test_group);
	free(test_group);
	return ret;
	}

	/* Simple test to verify the (z)swapin code paths */
	static int test_zswapin(const char *root)
	{
	int ret = KSFT_FAIL;
	char *test_group;
	long zswpin;

	test_group = cg_name(root, "zswapin_test");
	if (!test_group)
	goto out;
	if (cg_create(test_group))
	goto out;
	if (cg_write(test_group, "memory.max", "8M"))
	goto out;
	if (cg_write(test_group, "memory.zswap.max", "max"))
	goto out;

	/* Allocate and read more than memory.max to trigger (z)swap in */
	if (cg_run(test_group, allocate_and_read_bytes, (void *)MB(32)))
	goto out;

	zswpin = cg_read_key_long(test_group, "memory.stat", "zswpin ");
	if (zswpin < 0) {
	ksft_print_msg("failed to get zswpin\n");
	goto out;
	}

	if (zswpin < MB(24) / PAGE_SIZE) {
	ksft_print_msg("at least 24MB should be brought back from zswap\n");
	goto out;
	}

	ret = KSFT_PASS;

	out:
	cg_destroy(test_group);
	free(test_group);
	return ret;
	}

	/*
	* When trying to store a memcg page in zswap, if the memcg hits its memory
	* limit in zswap, writeback should affect only the zswapped pages of that
	* memcg.
	*/
	static int test_no_invasive_cgroup_shrink(const char *root)
	{
	int ret = KSFT_FAIL;
	size_t control_allocation_size = MB(10);
	char control_allocation, wb_group = NULL, *control_group = NULL;

	wb_group = setup_test_group_1M(root, "per_memcg_wb_test1");
	if (!wb_group)
	return KSFT_FAIL;
	if (cg_write(wb_group, "memory.zswap.max", "10K"))
	goto out;
	control_group = setup_test_group_1M(root, "per_memcg_wb_test2");
	if (!control_group)
	goto out;

	/* Push some test_group2 memory into zswap */
	if (cg_enter_current(control_group))
	goto out;
	control_allocation = malloc(control_allocation_size);
	for (int i = 0; i < control_allocation_size; i += 4095)
	control_allocation[i] = 'a';
	if (cg_read_key_long(control_group, "memory.stat", "zswapped") < 1)
	goto out;

	/* Allocate 10x memory.max to push wb_group memory into zswap and trigger wb */
	if (cg_run(wb_group, allocate_bytes, (void *)MB(10)))
	goto out;

	/* Verify that only zswapped memory from gwb_group has been written back */
	if (get_cg_wb_count(wb_group) > 0 && get_cg_wb_count(control_group) == 0)
	ret = KSFT_PASS;
	out:
	cg_enter_current(root);
	if (control_group) {
	cg_destroy(control_group);
	free(control_group);
	}
	cg_destroy(wb_group);
	free(wb_group);
	if (control_allocation)
	free(control_allocation);
	return ret;
	}

	struct no_kmem_bypass_child_args {
	size_t target_alloc_bytes;
	size_t child_allocated;
	};

	static int no_kmem_bypass_child(const char cgroup, void arg)
	{
	struct no_kmem_bypass_child_args *values = arg;
	void *allocation;

	allocation = malloc(values->target_alloc_bytes);
	if (!allocation) {
	values->child_allocated = true;
	return -1;
	}
	for (long i = 0; i < values->target_alloc_bytes; i += 4095)
	((char *)allocation)[i] = 'a';
	values->child_allocated = true;
	pause();
	free(allocation);
	return 0;
	}

	/*
	* When pages owned by a memcg are pushed to zswap by kswapd, they should be
	* charged to that cgroup. This wasn't the case before commit
	* cd08d80ecdac("mm: correctly charge compressed memory to its memcg").
	*
	* The test first allocates memory in a memcg, then raises min_free_kbytes to
	* a very high value so that the allocation falls below low wm, then makes
	* another allocation to trigger kswapd that should push the memcg-owned pages
	* to zswap and verifies that the zswap pages are correctly charged.
	*
	* To be run on a VM with at most 4G of memory.
	*/
	static int test_no_kmem_bypass(const char *root)
	{
	size_t min_free_kb_high, min_free_kb_low, min_free_kb_original;
	struct no_kmem_bypass_child_args *values;
	size_t trigger_allocation_size;
	int wait_child_iteration = 0;
	long stored_pages_threshold;
	struct sysinfo sys_info;
	int ret = KSFT_FAIL;
	int child_status;
	char *test_group;
	pid_t child_pid;

	/* Read sys info and compute test values accordingly */
	if (sysinfo(&sys_info) != 0)
	return KSFT_FAIL;
	if (sys_info.totalram > 5000000000)
	return KSFT_SKIP;
	values = mmap(0, sizeof(struct no_kmem_bypass_child_args), PROT_READ \|
	PROT_WRITE, MAP_SHARED \| MAP_ANONYMOUS, -1, 0);
	if (values == MAP_FAILED)
	return KSFT_FAIL;
	if (read_min_free_kb(&min_free_kb_original))
	return KSFT_FAIL;
	min_free_kb_high = sys_info.totalram / 2000;
	min_free_kb_low = sys_info.totalram / 500000;
	values->target_alloc_bytes = (sys_info.totalram - min_free_kb_high * 1000) +
	sys_info.totalram * 5 / 100;
	stored_pages_threshold = sys_info.totalram / 5 / 4096;
	trigger_allocation_size = sys_info.totalram / 20;

	/* Set up test memcg */
	if (cg_write(root, "cgroup.subtree_control", "+memory"))
	goto out;
	test_group = cg_name(root, "kmem_bypass_test");
	if (!test_group)
	goto out;

	/* Spawn memcg child and wait for it to allocate */
	set_min_free_kb(min_free_kb_low);
	if (cg_create(test_group))
	goto out;
	values->child_allocated = false;
	child_pid = cg_run_nowait(test_group, no_kmem_bypass_child, values);
	if (child_pid < 0)
	goto out;
	while (!values->child_allocated && wait_child_iteration++ < 10000)
	usleep(1000);

	/* Try to wakeup kswapd and let it push child memory to zswap */
	set_min_free_kb(min_free_kb_high);
	for (int i = 0; i < 20; i++) {
	size_t stored_pages;
	char *trigger_allocation = malloc(trigger_allocation_size);

	if (!trigger_allocation)
	break;
	for (int i = 0; i < trigger_allocation_size; i += 4095)
	trigger_allocation[i] = 'b';
	usleep(100000);
	free(trigger_allocation);
	if (get_zswap_stored_pages(&stored_pages))
	break;
	if (stored_pages < 0)
	break;
	/* If memory was pushed to zswap, verify it belongs to memcg */
	if (stored_pages > stored_pages_threshold) {
	int zswapped = cg_read_key_long(test_group, "memory.stat", "zswapped ");
	int delta = stored_pages * 4096 - zswapped;
	int result_ok = delta < stored_pages * 4096 / 4;

	ret = result_ok ? KSFT_PASS : KSFT_FAIL;
	break;
	}
	}

	kill(child_pid, SIGTERM);
	waitpid(child_pid, &child_status, 0);
	out:
	set_min_free_kb(min_free_kb_original);
	cg_destroy(test_group);
	free(test_group);
	return ret;
	}

	#define T(x) { x, #x }
	struct zswap_test {
	int (fn)(const char root);
	const char *name;
	} tests[] = {
	T(test_zswap_usage),
	T(test_swapin_nozswap),
	T(test_zswapin),
	T(test_no_kmem_bypass),
	T(test_no_invasive_cgroup_shrink),
	};
	#undef T

	static bool zswap_configured(void)
	{
	return access("/sys/module/zswap", F_OK) == 0;
	}

	int main(int argc, char **argv)
	{
	char root[PATH_MAX];
	int i, ret = EXIT_SUCCESS;

	if (cg_find_unified_root(root, sizeof(root)))
	ksft_exit_skip("cgroup v2 isn't mounted\n");

	if (!zswap_configured())
	ksft_exit_skip("zswap isn't configured\n");

	/*
	* Check that memory controller is available:
	* memory is listed in cgroup.controllers
	*/
	if (cg_read_strstr(root, "cgroup.controllers", "memory"))
	ksft_exit_skip("memory controller isn't available\n");

	if (cg_read_strstr(root, "cgroup.subtree_control", "memory"))
	if (cg_write(root, "cgroup.subtree_control", "+memory"))
	ksft_exit_skip("Failed to set memory controller\n");

	for (i = 0; i < ARRAY_SIZE(tests); i++) {
	switch (tests[i].fn(root)) {
	case KSFT_PASS:
	ksft_test_result_pass("%s\n", tests[i].name);
	break;
	case KSFT_SKIP:
	ksft_test_result_skip("%s\n", tests[i].name);
	break;
	default:
	ret = EXIT_FAILURE;
	ksft_test_result_fail("%s\n", tests[i].name);
	break;
	}
	}

	return ret;
	}