#define _GNU_SOURCE
#include <fcntl.h>
#include <limits.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <unistd.h>

#include <sys/mman.h>
#include <sys/wait.h>

#ifndef MADV_PAGEOUT
#define MADV_PAGEOUT 21
#endif

#define BASE_ADDR ((void *)(1UL << 30))
static unsigned long hpage_pmd_size;
static unsigned long page_size;
static int hpage_pmd_nr;

#define THP_SYSFS "/sys/kernel/mm/transparent_hugepage/"
#define PID_SMAPS "/proc/self/smaps"

enum thp_enabled {
	THP_ALWAYS,
	THP_MADVISE,
	THP_NEVER,
};

static const char *thp_enabled_strings[] = {
	"always",
	"madvise",
	"never",
	NULL
};

enum thp_defrag {
	THP_DEFRAG_ALWAYS,
	THP_DEFRAG_DEFER,
	THP_DEFRAG_DEFER_MADVISE,
	THP_DEFRAG_MADVISE,
	THP_DEFRAG_NEVER,
};

static const char *thp_defrag_strings[] = {
	"always",
	"defer",
	"defer+madvise",
	"madvise",
	"never",
	NULL
};

enum shmem_enabled {
	SHMEM_ALWAYS,
	SHMEM_WITHIN_SIZE,
	SHMEM_ADVISE,
	SHMEM_NEVER,
	SHMEM_DENY,
	SHMEM_FORCE,
};

static const char *shmem_enabled_strings[] = {
	"always",
	"within_size",
	"advise",
	"never",
	"deny",
	"force",
	NULL
};

struct khugepaged_settings {
	bool defrag;
	unsigned int alloc_sleep_millisecs;
	unsigned int scan_sleep_millisecs;
	unsigned int max_ptes_none;
	unsigned int max_ptes_swap;
	unsigned int max_ptes_shared;
	unsigned long pages_to_scan;
};

struct settings {
	enum thp_enabled thp_enabled;
	enum thp_defrag thp_defrag;
	enum shmem_enabled shmem_enabled;
	bool debug_cow;
	bool use_zero_page;
	struct khugepaged_settings khugepaged;
};

static struct settings default_settings = {
	.thp_enabled = THP_MADVISE,
	.thp_defrag = THP_DEFRAG_ALWAYS,
	.shmem_enabled = SHMEM_NEVER,
	.debug_cow = 0,
	.use_zero_page = 0,
	.khugepaged = {
		.defrag = 1,
		.alloc_sleep_millisecs = 10,
		.scan_sleep_millisecs = 10,
	},
};

static struct settings saved_settings;
static bool skip_settings_restore;

static int exit_status;

static void success(const char *msg)
{
	printf(" \e[32m%s\e[0m\n", msg);
}

static void fail(const char *msg)
{
	printf(" \e[31m%s\e[0m\n", msg);
	exit_status++;
}

static int read_file(const char *path, char *buf, size_t buflen)
{
	int fd;
	ssize_t numread;

	fd = open(path, O_RDONLY);
	if (fd == -1)
		return 0;

	numread = read(fd, buf, buflen - 1);
	if (numread < 1) {
		close(fd);
		return 0;
	}

	buf[numread] = '\0';
	close(fd);

	return (unsigned int) numread;
}

static int write_file(const char *path, const char *buf, size_t buflen)
{
	int fd;
	ssize_t numwritten;

	fd = open(path, O_WRONLY);
	if (fd == -1)
		return 0;

	numwritten = write(fd, buf, buflen - 1);
	close(fd);
	if (numwritten < 1)
		return 0;

	return (unsigned int) numwritten;
}

static int read_string(const char *name, const char *strings[])
{
	char path[PATH_MAX];
	char buf[256];
	char *c;
	int ret;

	ret = snprintf(path, PATH_MAX, THP_SYSFS "%s", name);
	if (ret >= PATH_MAX) {
		printf("%s: Pathname is too long\n", __func__);
		exit(EXIT_FAILURE);
	}

	if (!read_file(path, buf, sizeof(buf))) {
		perror(path);
		exit(EXIT_FAILURE);
	}

	c = strchr(buf, '[');
	if (!c) {
		printf("%s: Parse failure\n", __func__);
		exit(EXIT_FAILURE);
	}

	c++;
	memmove(buf, c, sizeof(buf) - (c - buf));

	c = strchr(buf, ']');
	if (!c) {
		printf("%s: Parse failure\n", __func__);
		exit(EXIT_FAILURE);
	}
	*c = '\0';

	ret = 0;
	while (strings[ret]) {
		if (!strcmp(strings[ret], buf))
			return ret;
		ret++;
	}

	printf("Failed to parse %s\n", name);
	exit(EXIT_FAILURE);
}

static void write_string(const char *name, const char *val)
{
	char path[PATH_MAX];
	int ret;

	ret = snprintf(path, PATH_MAX, THP_SYSFS "%s", name);
	if (ret >= PATH_MAX) {
		printf("%s: Pathname is too long\n", __func__);
		exit(EXIT_FAILURE);
	}

	if (!write_file(path, val, strlen(val) + 1)) {
		perror(path);
		exit(EXIT_FAILURE);
	}
}

static const unsigned long read_num(const char *name)
{
	char path[PATH_MAX];
	char buf[21];
	int ret;

	ret = snprintf(path, PATH_MAX, THP_SYSFS "%s", name);
	if (ret >= PATH_MAX) {
		printf("%s: Pathname is too long\n", __func__);
		exit(EXIT_FAILURE);
	}

	ret = read_file(path, buf, sizeof(buf));
	if (ret < 0) {
		perror("read_file(read_num)");
		exit(EXIT_FAILURE);
	}

	return strtoul(buf, NULL, 10);
}

static void write_num(const char *name, unsigned long num)
{
	char path[PATH_MAX];
	char buf[21];
	int ret;

	ret = snprintf(path, PATH_MAX, THP_SYSFS "%s", name);
	if (ret >= PATH_MAX) {
		printf("%s: Pathname is too long\n", __func__);
		exit(EXIT_FAILURE);
	}

	sprintf(buf, "%ld", num);
	if (!write_file(path, buf, strlen(buf) + 1)) {
		perror(path);
		exit(EXIT_FAILURE);
	}
}

static void write_settings(struct settings *settings)
{
	struct khugepaged_settings *khugepaged = &settings->khugepaged;

	write_string("enabled", thp_enabled_strings[settings->thp_enabled]);
	write_string("defrag", thp_defrag_strings[settings->thp_defrag]);
	write_string("shmem_enabled",
			shmem_enabled_strings[settings->shmem_enabled]);
	write_num("debug_cow", settings->debug_cow);
	write_num("use_zero_page", settings->use_zero_page);

	write_num("khugepaged/defrag", khugepaged->defrag);
	write_num("khugepaged/alloc_sleep_millisecs",
			khugepaged->alloc_sleep_millisecs);
	write_num("khugepaged/scan_sleep_millisecs",
			khugepaged->scan_sleep_millisecs);
	write_num("khugepaged/max_ptes_none", khugepaged->max_ptes_none);
	write_num("khugepaged/max_ptes_swap", khugepaged->max_ptes_swap);
	write_num("khugepaged/max_ptes_shared", khugepaged->max_ptes_shared);
	write_num("khugepaged/pages_to_scan", khugepaged->pages_to_scan);
}

static void restore_settings(int sig)
{
	if (skip_settings_restore)
		goto out;

	printf("Restore THP and khugepaged settings...");
	write_settings(&saved_settings);
	success("OK");
	if (sig)
		exit(EXIT_FAILURE);
out:
	exit(exit_status);
}

static void save_settings(void)
{
	printf("Save THP and khugepaged settings...");
	saved_settings = (struct settings) {
		.thp_enabled = read_string("enabled", thp_enabled_strings),
		.thp_defrag = read_string("defrag", thp_defrag_strings),
		.shmem_enabled =
			read_string("shmem_enabled", shmem_enabled_strings),
		.debug_cow = read_num("debug_cow"),
		.use_zero_page = read_num("use_zero_page"),
	};
	saved_settings.khugepaged = (struct khugepaged_settings) {
		.defrag = read_num("khugepaged/defrag"),
		.alloc_sleep_millisecs =
			read_num("khugepaged/alloc_sleep_millisecs"),
		.scan_sleep_millisecs =
			read_num("khugepaged/scan_sleep_millisecs"),
		.max_ptes_none = read_num("khugepaged/max_ptes_none"),
		.max_ptes_swap = read_num("khugepaged/max_ptes_swap"),
		.max_ptes_shared = read_num("khugepaged/max_ptes_shared"),
		.pages_to_scan = read_num("khugepaged/pages_to_scan"),
	};
	success("OK");

	signal(SIGTERM, restore_settings);
	signal(SIGINT, restore_settings);
	signal(SIGHUP, restore_settings);
	signal(SIGQUIT, restore_settings);
}

static void adjust_settings(void)
{

	printf("Adjust settings...");
	write_settings(&default_settings);
	success("OK");
}

#define MAX_LINE_LENGTH 500

static bool check_for_pattern(FILE *fp, char *pattern, char *buf)
{
	while (fgets(buf, MAX_LINE_LENGTH, fp) != NULL) {
		if (!strncmp(buf, pattern, strlen(pattern)))
			return true;
	}
	return false;
}

static bool check_huge(void *addr)
{
	bool thp = false;
	int ret;
	FILE *fp;
	char buffer[MAX_LINE_LENGTH];
	char addr_pattern[MAX_LINE_LENGTH];

	ret = snprintf(addr_pattern, MAX_LINE_LENGTH, "%08lx-",
		       (unsigned long) addr);
	if (ret >= MAX_LINE_LENGTH) {
		printf("%s: Pattern is too long\n", __func__);
		exit(EXIT_FAILURE);
	}


	fp = fopen(PID_SMAPS, "r");
	if (!fp) {
		printf("%s: Failed to open file %s\n", __func__, PID_SMAPS);
		exit(EXIT_FAILURE);
	}
	if (!check_for_pattern(fp, addr_pattern, buffer))
		goto err_out;

	ret = snprintf(addr_pattern, MAX_LINE_LENGTH, "AnonHugePages:%10ld kB",
		       hpage_pmd_size >> 10);
	if (ret >= MAX_LINE_LENGTH) {
		printf("%s: Pattern is too long\n", __func__);
		exit(EXIT_FAILURE);
	}
	/*
	 * Fetch the AnonHugePages: in the same block and check whether it got
	 * the expected number of hugeepages next.
	 */
	if (!check_for_pattern(fp, "AnonHugePages:", buffer))
		goto err_out;

	if (strncmp(buffer, addr_pattern, strlen(addr_pattern)))
		goto err_out;

	thp = true;
err_out:
	fclose(fp);
	return thp;
}


static bool check_swap(void *addr, unsigned long size)
{
	bool swap = false;
	int ret;
	FILE *fp;
	char buffer[MAX_LINE_LENGTH];
	char addr_pattern[MAX_LINE_LENGTH];

	ret = snprintf(addr_pattern, MAX_LINE_LENGTH, "%08lx-",
		       (unsigned long) addr);
	if (ret >= MAX_LINE_LENGTH) {
		printf("%s: Pattern is too long\n", __func__);
		exit(EXIT_FAILURE);
	}


	fp = fopen(PID_SMAPS, "r");
	if (!fp) {
		printf("%s: Failed to open file %s\n", __func__, PID_SMAPS);
		exit(EXIT_FAILURE);
	}
	if (!check_for_pattern(fp, addr_pattern, buffer))
		goto err_out;

	ret = snprintf(addr_pattern, MAX_LINE_LENGTH, "Swap:%19ld kB",
		       size >> 10);
	if (ret >= MAX_LINE_LENGTH) {
		printf("%s: Pattern is too long\n", __func__);
		exit(EXIT_FAILURE);
	}
	/*
	 * Fetch the Swap: in the same block and check whether it got
	 * the expected number of hugeepages next.
	 */
	if (!check_for_pattern(fp, "Swap:", buffer))
		goto err_out;

	if (strncmp(buffer, addr_pattern, strlen(addr_pattern)))
		goto err_out;

	swap = true;
err_out:
	fclose(fp);
	return swap;
}

static void *alloc_mapping(void)
{
	void *p;

	p = mmap(BASE_ADDR, hpage_pmd_size, PROT_READ | PROT_WRITE,
			MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
	if (p != BASE_ADDR) {
		printf("Failed to allocate VMA at %p\n", BASE_ADDR);
		exit(EXIT_FAILURE);
	}

	return p;
}

static void fill_memory(int *p, unsigned long start, unsigned long end)
{
	int i;

	for (i = start / page_size; i < end / page_size; i++)
		p[i * page_size / sizeof(*p)] = i + 0xdead0000;
}

static void validate_memory(int *p, unsigned long start, unsigned long end)
{
	int i;

	for (i = start / page_size; i < end / page_size; i++) {
		if (p[i * page_size / sizeof(*p)] != i + 0xdead0000) {
			printf("Page %d is corrupted: %#x\n",
					i, p[i * page_size / sizeof(*p)]);
			exit(EXIT_FAILURE);
		}
	}
}

#define TICK 500000
static bool wait_for_scan(const char *msg, char *p)
{
	int full_scans;
	int timeout = 6; /* 3 seconds */

	/* Sanity check */
	if (check_huge(p)) {
		printf("Unexpected huge page\n");
		exit(EXIT_FAILURE);
	}

	madvise(p, hpage_pmd_size, MADV_HUGEPAGE);

	/* Wait until the second full_scan completed */
	full_scans = read_num("khugepaged/full_scans") + 2;

	printf("%s...", msg);
	while (timeout--) {
		if (check_huge(p))
			break;
		if (read_num("khugepaged/full_scans") >= full_scans)
			break;
		printf(".");
		usleep(TICK);
	}

	madvise(p, hpage_pmd_size, MADV_NOHUGEPAGE);

	return timeout == -1;
}

static void alloc_at_fault(void)
{
	struct settings settings = default_settings;
	char *p;

	settings.thp_enabled = THP_ALWAYS;
	write_settings(&settings);

	p = alloc_mapping();
	*p = 1;
	printf("Allocate huge page on fault...");
	if (check_huge(p))
		success("OK");
	else
		fail("Fail");

	write_settings(&default_settings);

	madvise(p, page_size, MADV_DONTNEED);
	printf("Split huge PMD on MADV_DONTNEED...");
	if (!check_huge(p))
		success("OK");
	else
		fail("Fail");
	munmap(p, hpage_pmd_size);
}

static void collapse_full(void)
{
	void *p;

	p = alloc_mapping();
	fill_memory(p, 0, hpage_pmd_size);
	if (wait_for_scan("Collapse fully populated PTE table", p))
		fail("Timeout");
	else if (check_huge(p))
		success("OK");
	else
		fail("Fail");
	validate_memory(p, 0, hpage_pmd_size);
	munmap(p, hpage_pmd_size);
}

static void collapse_empty(void)
{
	void *p;

	p = alloc_mapping();
	if (wait_for_scan("Do not collapse empty PTE table", p))
		fail("Timeout");
	else if (check_huge(p))
		fail("Fail");
	else
		success("OK");
	munmap(p, hpage_pmd_size);
}

static void collapse_single_pte_entry(void)
{
	void *p;

	p = alloc_mapping();
	fill_memory(p, 0, page_size);
	if (wait_for_scan("Collapse PTE table with single PTE entry present", p))
		fail("Timeout");
	else if (check_huge(p))
		success("OK");
	else
		fail("Fail");
	validate_memory(p, 0, page_size);
	munmap(p, hpage_pmd_size);
}

static void collapse_max_ptes_none(void)
{
	int max_ptes_none = hpage_pmd_nr / 2;
	struct settings settings = default_settings;
	void *p;

	settings.khugepaged.max_ptes_none = max_ptes_none;
	write_settings(&settings);

	p = alloc_mapping();

	fill_memory(p, 0, (hpage_pmd_nr - max_ptes_none - 1) * page_size);
	if (wait_for_scan("Do not collapse with max_ptes_none exceeded", p))
		fail("Timeout");
	else if (check_huge(p))
		fail("Fail");
	else
		success("OK");
	validate_memory(p, 0, (hpage_pmd_nr - max_ptes_none - 1) * page_size);

	fill_memory(p, 0, (hpage_pmd_nr - max_ptes_none) * page_size);
	if (wait_for_scan("Collapse with max_ptes_none PTEs empty", p))
		fail("Timeout");
	else if (check_huge(p))
		success("OK");
	else
		fail("Fail");
	validate_memory(p, 0, (hpage_pmd_nr - max_ptes_none) * page_size);

	munmap(p, hpage_pmd_size);
	write_settings(&default_settings);
}

static void collapse_swapin_single_pte(void)
{
	void *p;
	p = alloc_mapping();
	fill_memory(p, 0, hpage_pmd_size);

	printf("Swapout one page...");
	if (madvise(p, page_size, MADV_PAGEOUT)) {
		perror("madvise(MADV_PAGEOUT)");
		exit(EXIT_FAILURE);
	}
	if (check_swap(p, page_size)) {
		success("OK");
	} else {
		fail("Fail");
		goto out;
	}

	if (wait_for_scan("Collapse with swapping in single PTE entry", p))
		fail("Timeout");
	else if (check_huge(p))
		success("OK");
	else
		fail("Fail");
	validate_memory(p, 0, hpage_pmd_size);
out:
	munmap(p, hpage_pmd_size);
}

static void collapse_max_ptes_swap(void)
{
	int max_ptes_swap = read_num("khugepaged/max_ptes_swap");
	void *p;

	p = alloc_mapping();

	fill_memory(p, 0, hpage_pmd_size);
	printf("Swapout %d of %d pages...", max_ptes_swap + 1, hpage_pmd_nr);
	if (madvise(p, (max_ptes_swap + 1) * page_size, MADV_PAGEOUT)) {
		perror("madvise(MADV_PAGEOUT)");
		exit(EXIT_FAILURE);
	}
	if (check_swap(p, (max_ptes_swap + 1) * page_size)) {
		success("OK");
	} else {
		fail("Fail");
		goto out;
	}

	if (wait_for_scan("Do not collapse with max_ptes_swap exceeded", p))
		fail("Timeout");
	else if (check_huge(p))
		fail("Fail");
	else
		success("OK");
	validate_memory(p, 0, hpage_pmd_size);

	fill_memory(p, 0, hpage_pmd_size);
	printf("Swapout %d of %d pages...", max_ptes_swap, hpage_pmd_nr);
	if (madvise(p, max_ptes_swap * page_size, MADV_PAGEOUT)) {
		perror("madvise(MADV_PAGEOUT)");
		exit(EXIT_FAILURE);
	}
	if (check_swap(p, max_ptes_swap * page_size)) {
		success("OK");
	} else {
		fail("Fail");
		goto out;
	}

	if (wait_for_scan("Collapse with max_ptes_swap pages swapped out", p))
		fail("Timeout");
	else if (check_huge(p))
		success("OK");
	else
		fail("Fail");
	validate_memory(p, 0, hpage_pmd_size);
out:
	munmap(p, hpage_pmd_size);
}

static void collapse_single_pte_entry_compound(void)
{
	void *p;

	p = alloc_mapping();

	printf("Allocate huge page...");
	madvise(p, hpage_pmd_size, MADV_HUGEPAGE);
	fill_memory(p, 0, hpage_pmd_size);
	if (check_huge(p))
		success("OK");
	else
		fail("Fail");
	madvise(p, hpage_pmd_size, MADV_NOHUGEPAGE);

	printf("Split huge page leaving single PTE mapping compound page...");
	madvise(p + page_size, hpage_pmd_size - page_size, MADV_DONTNEED);
	if (!check_huge(p))
		success("OK");
	else
		fail("Fail");

	if (wait_for_scan("Collapse PTE table with single PTE mapping compound page", p))
		fail("Timeout");
	else if (check_huge(p))
		success("OK");
	else
		fail("Fail");
	validate_memory(p, 0, page_size);
	munmap(p, hpage_pmd_size);
}

static void collapse_full_of_compound(void)
{
	void *p;

	p = alloc_mapping();

	printf("Allocate huge page...");
	madvise(p, hpage_pmd_size, MADV_HUGEPAGE);
	fill_memory(p, 0, hpage_pmd_size);
	if (check_huge(p))
		success("OK");
	else
		fail("Fail");

	printf("Split huge page leaving single PTE page table full of compound pages...");
	madvise(p, page_size, MADV_NOHUGEPAGE);
	madvise(p, hpage_pmd_size, MADV_NOHUGEPAGE);
	if (!check_huge(p))
		success("OK");
	else
		fail("Fail");

	if (wait_for_scan("Collapse PTE table full of compound pages", p))
		fail("Timeout");
	else if (check_huge(p))
		success("OK");
	else
		fail("Fail");
	validate_memory(p, 0, hpage_pmd_size);
	munmap(p, hpage_pmd_size);
}

static void collapse_compound_extreme(void)
{
	void *p;
	int i;

	p = alloc_mapping();
	for (i = 0; i < hpage_pmd_nr; i++) {
		printf("\rConstruct PTE page table full of different PTE-mapped compound pages %3d/%d...",
				i + 1, hpage_pmd_nr);

		madvise(BASE_ADDR, hpage_pmd_size, MADV_HUGEPAGE);
		fill_memory(BASE_ADDR, 0, hpage_pmd_size);
		if (!check_huge(BASE_ADDR)) {
			printf("Failed to allocate huge page\n");
			exit(EXIT_FAILURE);
		}
		madvise(BASE_ADDR, hpage_pmd_size, MADV_NOHUGEPAGE);

		p = mremap(BASE_ADDR - i * page_size,
				i * page_size + hpage_pmd_size,
				(i + 1) * page_size,
				MREMAP_MAYMOVE | MREMAP_FIXED,
				BASE_ADDR + 2 * hpage_pmd_size);
		if (p == MAP_FAILED) {
			perror("mremap+unmap");
			exit(EXIT_FAILURE);
		}

		p = mremap(BASE_ADDR + 2 * hpage_pmd_size,
				(i + 1) * page_size,
				(i + 1) * page_size + hpage_pmd_size,
				MREMAP_MAYMOVE | MREMAP_FIXED,
				BASE_ADDR - (i + 1) * page_size);
		if (p == MAP_FAILED) {
			perror("mremap+alloc");
			exit(EXIT_FAILURE);
		}
	}

	munmap(BASE_ADDR, hpage_pmd_size);
	fill_memory(p, 0, hpage_pmd_size);
	if (!check_huge(p))
		success("OK");
	else
		fail("Fail");

	if (wait_for_scan("Collapse PTE table full of different compound pages", p))
		fail("Timeout");
	else if (check_huge(p))
		success("OK");
	else
		fail("Fail");

	validate_memory(p, 0, hpage_pmd_size);
	munmap(p, hpage_pmd_size);
}

static void collapse_fork(void)
{
	int wstatus;
	void *p;

	p = alloc_mapping();

	printf("Allocate small page...");
	fill_memory(p, 0, page_size);
	if (!check_huge(p))
		success("OK");
	else
		fail("Fail");

	printf("Share small page over fork()...");
	if (!fork()) {
		/* Do not touch settings on child exit */
		skip_settings_restore = true;
		exit_status = 0;

		if (!check_huge(p))
			success("OK");
		else
			fail("Fail");

		fill_memory(p, page_size, 2 * page_size);

		if (wait_for_scan("Collapse PTE table with single page shared with parent process", p))
			fail("Timeout");
		else if (check_huge(p))
			success("OK");
		else
			fail("Fail");

		validate_memory(p, 0, page_size);
		munmap(p, hpage_pmd_size);
		exit(exit_status);
	}

	wait(&wstatus);
	exit_status += WEXITSTATUS(wstatus);

	printf("Check if parent still has small page...");
	if (!check_huge(p))
		success("OK");
	else
		fail("Fail");
	validate_memory(p, 0, page_size);
	munmap(p, hpage_pmd_size);
}

static void collapse_fork_compound(void)
{
	int wstatus;
	void *p;

	p = alloc_mapping();

	printf("Allocate huge page...");
	madvise(p, hpage_pmd_size, MADV_HUGEPAGE);
	fill_memory(p, 0, hpage_pmd_size);
	if (check_huge(p))
		success("OK");
	else
		fail("Fail");

	printf("Share huge page over fork()...");
	if (!fork()) {
		/* Do not touch settings on child exit */
		skip_settings_restore = true;
		exit_status = 0;

		if (check_huge(p))
			success("OK");
		else
			fail("Fail");

		printf("Split huge page PMD in child process...");
		madvise(p, page_size, MADV_NOHUGEPAGE);
		madvise(p, hpage_pmd_size, MADV_NOHUGEPAGE);
		if (!check_huge(p))
			success("OK");
		else
			fail("Fail");
		fill_memory(p, 0, page_size);

		write_num("khugepaged/max_ptes_shared", hpage_pmd_nr - 1);
		if (wait_for_scan("Collapse PTE table full of compound pages in child", p))
			fail("Timeout");
		else if (check_huge(p))
			success("OK");
		else
			fail("Fail");
		write_num("khugepaged/max_ptes_shared",
				default_settings.khugepaged.max_ptes_shared);

		validate_memory(p, 0, hpage_pmd_size);
		munmap(p, hpage_pmd_size);
		exit(exit_status);
	}

	wait(&wstatus);
	exit_status += WEXITSTATUS(wstatus);

	printf("Check if parent still has huge page...");
	if (check_huge(p))
		success("OK");
	else
		fail("Fail");
	validate_memory(p, 0, hpage_pmd_size);
	munmap(p, hpage_pmd_size);
}

static void collapse_max_ptes_shared()
{
	int max_ptes_shared = read_num("khugepaged/max_ptes_shared");
	int wstatus;
	void *p;

	p = alloc_mapping();

	printf("Allocate huge page...");
	madvise(p, hpage_pmd_size, MADV_HUGEPAGE);
	fill_memory(p, 0, hpage_pmd_size);
	if (check_huge(p))
		success("OK");
	else
		fail("Fail");

	printf("Share huge page over fork()...");
	if (!fork()) {
		/* Do not touch settings on child exit */
		skip_settings_restore = true;
		exit_status = 0;

		if (check_huge(p))
			success("OK");
		else
			fail("Fail");

		printf("Trigger CoW on page %d of %d...",
				hpage_pmd_nr - max_ptes_shared - 1, hpage_pmd_nr);
		fill_memory(p, 0, (hpage_pmd_nr - max_ptes_shared - 1) * page_size);
		if (!check_huge(p))
			success("OK");
		else
			fail("Fail");

		if (wait_for_scan("Do not collapse with max_ptes_shared exceeded", p))
			fail("Timeout");
		else if (!check_huge(p))
			success("OK");
		else
			fail("Fail");

		printf("Trigger CoW on page %d of %d...",
				hpage_pmd_nr - max_ptes_shared, hpage_pmd_nr);
		fill_memory(p, 0, (hpage_pmd_nr - max_ptes_shared) * page_size);
		if (!check_huge(p))
			success("OK");
		else
			fail("Fail");


		if (wait_for_scan("Collapse with max_ptes_shared PTEs shared", p))
			fail("Timeout");
		else if (check_huge(p))
			success("OK");
		else
			fail("Fail");

		validate_memory(p, 0, hpage_pmd_size);
		munmap(p, hpage_pmd_size);
		exit(exit_status);
	}

	wait(&wstatus);
	exit_status += WEXITSTATUS(wstatus);

	printf("Check if parent still has huge page...");
	if (check_huge(p))
		success("OK");
	else
		fail("Fail");
	validate_memory(p, 0, hpage_pmd_size);
	munmap(p, hpage_pmd_size);
}

int main(void)
{
	setbuf(stdout, NULL);

	page_size = getpagesize();
	hpage_pmd_size = read_num("hpage_pmd_size");
	hpage_pmd_nr = hpage_pmd_size / page_size;

	default_settings.khugepaged.max_ptes_none = hpage_pmd_nr - 1;
	default_settings.khugepaged.max_ptes_swap = hpage_pmd_nr / 8;
	default_settings.khugepaged.max_ptes_shared = hpage_pmd_nr / 2;
	default_settings.khugepaged.pages_to_scan = hpage_pmd_nr * 8;

	save_settings();
	adjust_settings();

	alloc_at_fault();
	collapse_full();
	collapse_empty();
	collapse_single_pte_entry();
	collapse_max_ptes_none();
	collapse_swapin_single_pte();
	collapse_max_ptes_swap();
	collapse_single_pte_entry_compound();
	collapse_full_of_compound();
	collapse_compound_extreme();
	collapse_fork();
	collapse_fork_compound();
	collapse_max_ptes_shared();

	restore_settings(0);
}