selftests/mm: factor out thp settings management

The khugepaged test has a useful framework for save/restore/pop/push of
all thp settings via the sysfs interface.  This will be useful to
explicitly control multi-size THP settings in other tests, so let's move
it out of khugepaged and into its own thp_settings.[c|h] utility.

Link: https://lkml.kernel.org/r/20231207161211.2374093-7-ryan.roberts@arm.comSigned-off-by: Ryan Roberts <ryan.roberts@arm.com>
Tested-by: Alistair Popple <apopple@nvidia.com>
Acked-by: David Hildenbrand <david@redhat.com>
Tested-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Tested-by: John Hubbard <jhubbard@nvidia.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Barry Song <v-songbaohua@oppo.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Rientjes <rientjes@google.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Itaru Kitayama <itaru.kitayama@gmail.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yin Fengwei <fengwei.yin@intel.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tools/testing/selftests/mm/Makefile

@@ -117,8 +117,8 @@ TEST_FILES += va_high_addr_switch.sh
 
 include ../lib.mk
 
-$(TEST_GEN_PROGS): vm_util.c
-$(TEST_GEN_FILES): vm_util.c
+$(TEST_GEN_PROGS): vm_util.c thp_settings.c
+$(TEST_GEN_FILES): vm_util.c thp_settings.c
 
 $(OUTPUT)/uffd-stress: uffd-common.c
 $(OUTPUT)/uffd-unit-tests: uffd-common.c

tools/testing/selftests/mm/thp_settings.c

+// SPDX-License-Identifier: GPL-2.0
+#include <fcntl.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "thp_settings.h"
+
+#define THP_SYSFS "/sys/kernel/mm/transparent_hugepage/"
+#define MAX_SETTINGS_DEPTH 4
+static struct thp_settings settings_stack[MAX_SETTINGS_DEPTH];
+static int settings_index;
+static struct thp_settings saved_settings;
+static char dev_queue_read_ahead_path[PATH_MAX];
+
+static const char * const thp_enabled_strings[] = {
+	"always",
+	"madvise",
+	"never",
+	NULL
+};
+
+static const char * const thp_defrag_strings[] = {
+	"always",
+	"defer",
+	"defer+madvise",
+	"madvise",
+	"never",
+	NULL
+};
+
+static const char * const shmem_enabled_strings[] = {
+	"always",
+	"within_size",
+	"advise",
+	"never",
+	"deny",
+	"force",
+	NULL
+};
+
+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;
+}
+
+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) {
+		printf("open(%s)\n", path);
+		exit(EXIT_FAILURE);
+		return 0;
+	}
+
+	numwritten = write(fd, buf, buflen - 1);
+	close(fd);
+	if (numwritten < 1) {
+		printf("write(%s)\n", buf);
+		exit(EXIT_FAILURE);
+		return 0;
+	}
+
+	return (unsigned int) numwritten;
+}
+
+const unsigned long read_num(const char *path)
+{
+	char buf[21];
+
+	if (read_file(path, buf, sizeof(buf)) < 0) {
+		perror("read_file()");
+		exit(EXIT_FAILURE);
+	}
+
+	return strtoul(buf, NULL, 10);
+}
+
+void write_num(const char *path, unsigned long num)
+{
+	char buf[21];
+
+	sprintf(buf, "%ld", num);
+	if (!write_file(path, buf, strlen(buf) + 1)) {
+		perror(path);
+		exit(EXIT_FAILURE);
+	}
+}
+
+int thp_read_string(const char *name, const char * const 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);
+}
+
+void thp_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);
+	}
+}
+
+const unsigned long thp_read_num(const char *name)
+{
+	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);
+	}
+	return read_num(path);
+}
+
+void thp_write_num(const char *name, unsigned long num)
+{
+	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);
+	}
+	write_num(path, num);
+}
+
+void thp_read_settings(struct thp_settings *settings)
+{
+	*settings = (struct thp_settings) {
+		.thp_enabled = thp_read_string("enabled", thp_enabled_strings),
+		.thp_defrag = thp_read_string("defrag", thp_defrag_strings),
+		.shmem_enabled =
+			thp_read_string("shmem_enabled", shmem_enabled_strings),
+		.use_zero_page = thp_read_num("use_zero_page"),
+	};
+	settings->khugepaged = (struct khugepaged_settings) {
+		.defrag = thp_read_num("khugepaged/defrag"),
+		.alloc_sleep_millisecs =
+			thp_read_num("khugepaged/alloc_sleep_millisecs"),
+		.scan_sleep_millisecs =
+			thp_read_num("khugepaged/scan_sleep_millisecs"),
+		.max_ptes_none = thp_read_num("khugepaged/max_ptes_none"),
+		.max_ptes_swap = thp_read_num("khugepaged/max_ptes_swap"),
+		.max_ptes_shared = thp_read_num("khugepaged/max_ptes_shared"),
+		.pages_to_scan = thp_read_num("khugepaged/pages_to_scan"),
+	};
+	if (dev_queue_read_ahead_path[0])
+		settings->read_ahead_kb = read_num(dev_queue_read_ahead_path);
+}
+
+void thp_write_settings(struct thp_settings *settings)
+{
+	struct khugepaged_settings *khugepaged = &settings->khugepaged;
+
+	thp_write_string("enabled", thp_enabled_strings[settings->thp_enabled]);
+	thp_write_string("defrag", thp_defrag_strings[settings->thp_defrag]);
+	thp_write_string("shmem_enabled",
+			shmem_enabled_strings[settings->shmem_enabled]);
+	thp_write_num("use_zero_page", settings->use_zero_page);
+
+	thp_write_num("khugepaged/defrag", khugepaged->defrag);
+	thp_write_num("khugepaged/alloc_sleep_millisecs",
+			khugepaged->alloc_sleep_millisecs);
+	thp_write_num("khugepaged/scan_sleep_millisecs",
+			khugepaged->scan_sleep_millisecs);
+	thp_write_num("khugepaged/max_ptes_none", khugepaged->max_ptes_none);
+	thp_write_num("khugepaged/max_ptes_swap", khugepaged->max_ptes_swap);
+	thp_write_num("khugepaged/max_ptes_shared", khugepaged->max_ptes_shared);
+	thp_write_num("khugepaged/pages_to_scan", khugepaged->pages_to_scan);
+
+	if (dev_queue_read_ahead_path[0])
+		write_num(dev_queue_read_ahead_path, settings->read_ahead_kb);
+}
+
+struct thp_settings *thp_current_settings(void)
+{
+	if (!settings_index) {
+		printf("Fail: No settings set");
+		exit(EXIT_FAILURE);
+	}
+	return settings_stack + settings_index - 1;
+}
+
+void thp_push_settings(struct thp_settings *settings)
+{
+	if (settings_index >= MAX_SETTINGS_DEPTH) {
+		printf("Fail: Settings stack exceeded");
+		exit(EXIT_FAILURE);
+	}
+	settings_stack[settings_index++] = *settings;
+	thp_write_settings(thp_current_settings());
+}
+
+void thp_pop_settings(void)
+{
+	if (settings_index <= 0) {
+		printf("Fail: Settings stack empty");
+		exit(EXIT_FAILURE);
+	}
+	--settings_index;
+	thp_write_settings(thp_current_settings());
+}
+
+void thp_restore_settings(void)
+{
+	thp_write_settings(&saved_settings);
+}
+
+void thp_save_settings(void)
+{
+	thp_read_settings(&saved_settings);
+}
+
+void thp_set_read_ahead_path(char *path)
+{
+	if (!path) {
+		dev_queue_read_ahead_path[0] = '\0';
+		return;
+	}
+
+	strncpy(dev_queue_read_ahead_path, path,
+		sizeof(dev_queue_read_ahead_path));
+	dev_queue_read_ahead_path[sizeof(dev_queue_read_ahead_path) - 1] = '\0';
+}

tools/testing/selftests/mm/thp_settings.h

+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __THP_SETTINGS_H__
+#define __THP_SETTINGS_H__
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+enum thp_enabled {
+	THP_ALWAYS,
+	THP_MADVISE,
+	THP_NEVER,
+};
+
+enum thp_defrag {
+	THP_DEFRAG_ALWAYS,
+	THP_DEFRAG_DEFER,
+	THP_DEFRAG_DEFER_MADVISE,
+	THP_DEFRAG_MADVISE,
+	THP_DEFRAG_NEVER,
+};
+
+enum shmem_enabled {
+	SHMEM_ALWAYS,
+	SHMEM_WITHIN_SIZE,
+	SHMEM_ADVISE,
+	SHMEM_NEVER,
+	SHMEM_DENY,
+	SHMEM_FORCE,
+};
+
+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 thp_settings {
+	enum thp_enabled thp_enabled;
+	enum thp_defrag thp_defrag;
+	enum shmem_enabled shmem_enabled;
+	bool use_zero_page;
+	struct khugepaged_settings khugepaged;
+	unsigned long read_ahead_kb;
+};
+
+int read_file(const char *path, char *buf, size_t buflen);
+int write_file(const char *path, const char *buf, size_t buflen);
+const unsigned long read_num(const char *path);
+void write_num(const char *path, unsigned long num);
+
+int thp_read_string(const char *name, const char * const strings[]);
+void thp_write_string(const char *name, const char *val);
+const unsigned long thp_read_num(const char *name);
+void thp_write_num(const char *name, unsigned long num);
+
+void thp_write_settings(struct thp_settings *settings);
+void thp_read_settings(struct thp_settings *settings);
+struct thp_settings *thp_current_settings(void);
+void thp_push_settings(struct thp_settings *settings);
+void thp_pop_settings(void);
+void thp_restore_settings(void);
+void thp_save_settings(void);
+
+void thp_set_read_ahead_path(char *path);
+
+#endif /* __THP_SETTINGS_H__ */