Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1829 insertions, 0 deletions

diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c
new file mode 100644
index 0000000000..b317f51dcc
--- /dev/null
+++ b/mm/damon/sysfs.c
@@ -0,0 +1,1829 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * DAMON sysfs Interface
+ *
+ * Copyright (c) 2022 SeongJae Park <sj@kernel.org>
+ */
+
+#include <linux/pid.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+
+#include "sysfs-common.h"
+
+/*
+ * init region directory
+ */
+
+struct damon_sysfs_region {
+	struct kobject kobj;
+	struct damon_addr_range ar;
+};
+
+static struct damon_sysfs_region *damon_sysfs_region_alloc(void)
+{
+	return kzalloc(sizeof(struct damon_sysfs_region), GFP_KERNEL);
+}
+
+static ssize_t start_show(struct kobject *kobj, struct kobj_attribute *attr,
+		char *buf)
+{
+	struct damon_sysfs_region *region = container_of(kobj,
+			struct damon_sysfs_region, kobj);
+
+	return sysfs_emit(buf, "%lu\n", region->ar.start);
+}
+
+static ssize_t start_store(struct kobject *kobj, struct kobj_attribute *attr,
+		const char *buf, size_t count)
+{
+	struct damon_sysfs_region *region = container_of(kobj,
+			struct damon_sysfs_region, kobj);
+	int err = kstrtoul(buf, 0, &region->ar.start);
+
+	return err ? err : count;
+}
+
+static ssize_t end_show(struct kobject *kobj, struct kobj_attribute *attr,
+		char *buf)
+{
+	struct damon_sysfs_region *region = container_of(kobj,
+			struct damon_sysfs_region, kobj);
+
+	return sysfs_emit(buf, "%lu\n", region->ar.end);
+}
+
+static ssize_t end_store(struct kobject *kobj, struct kobj_attribute *attr,
+		const char *buf, size_t count)
+{
+	struct damon_sysfs_region *region = container_of(kobj,
+			struct damon_sysfs_region, kobj);
+	int err = kstrtoul(buf, 0, &region->ar.end);
+
+	return err ? err : count;
+}
+
+static void damon_sysfs_region_release(struct kobject *kobj)
+{
+	kfree(container_of(kobj, struct damon_sysfs_region, kobj));
+}
+
+static struct kobj_attribute damon_sysfs_region_start_attr =
+		__ATTR_RW_MODE(start, 0600);
+
+static struct kobj_attribute damon_sysfs_region_end_attr =
+		__ATTR_RW_MODE(end, 0600);
+
+static struct attribute *damon_sysfs_region_attrs[] = {
+	&damon_sysfs_region_start_attr.attr,
+	&damon_sysfs_region_end_attr.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(damon_sysfs_region);
+
+static const struct kobj_type damon_sysfs_region_ktype = {
+	.release = damon_sysfs_region_release,
+	.sysfs_ops = &kobj_sysfs_ops,
+	.default_groups = damon_sysfs_region_groups,
+};
+
+/*
+ * init_regions directory
+ */
+
+struct damon_sysfs_regions {
+	struct kobject kobj;
+	struct damon_sysfs_region **regions_arr;
+	int nr;
+};
+
+static struct damon_sysfs_regions *damon_sysfs_regions_alloc(void)
+{
+	return kzalloc(sizeof(struct damon_sysfs_regions), GFP_KERNEL);
+}
+
+static void damon_sysfs_regions_rm_dirs(struct damon_sysfs_regions *regions)
+{
+	struct damon_sysfs_region **regions_arr = regions->regions_arr;
+	int i;
+
+	for (i = 0; i < regions->nr; i++)
+		kobject_put(&regions_arr[i]->kobj);
+	regions->nr = 0;
+	kfree(regions_arr);
+	regions->regions_arr = NULL;
+}
+
+static int damon_sysfs_regions_add_dirs(struct damon_sysfs_regions *regions,
+		int nr_regions)
+{
+	struct damon_sysfs_region **regions_arr, *region;
+	int err, i;
+
+	damon_sysfs_regions_rm_dirs(regions);
+	if (!nr_regions)
+		return 0;
+
+	regions_arr = kmalloc_array(nr_regions, sizeof(*regions_arr),
+			GFP_KERNEL | __GFP_NOWARN);
+	if (!regions_arr)
+		return -ENOMEM;
+	regions->regions_arr = regions_arr;
+
+	for (i = 0; i < nr_regions; i++) {
+		region = damon_sysfs_region_alloc();
+		if (!region) {
+			damon_sysfs_regions_rm_dirs(regions);
+			return -ENOMEM;
+		}
+
+		err = kobject_init_and_add(&region->kobj,
+				&damon_sysfs_region_ktype, &regions->kobj,
+				"%d", i);
+		if (err) {
+			kobject_put(&region->kobj);
+			damon_sysfs_regions_rm_dirs(regions);
+			return err;
+		}
+
+		regions_arr[i] = region;
+		regions->nr++;
+	}
+	return 0;
+}
+
+static ssize_t nr_regions_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	struct damon_sysfs_regions *regions = container_of(kobj,
+			struct damon_sysfs_regions, kobj);
+
+	return sysfs_emit(buf, "%d\n", regions->nr);
+}
+
+static ssize_t nr_regions_store(struct kobject *kobj,
+		struct kobj_attribute *attr, const char *buf, size_t count)
+{
+	struct damon_sysfs_regions *regions;
+	int nr, err = kstrtoint(buf, 0, &nr);
+
+	if (err)
+		return err;
+	if (nr < 0)
+		return -EINVAL;
+
+	regions = container_of(kobj, struct damon_sysfs_regions, kobj);
+
+	if (!mutex_trylock(&damon_sysfs_lock))
+		return -EBUSY;
+	err = damon_sysfs_regions_add_dirs(regions, nr);
+	mutex_unlock(&damon_sysfs_lock);
+	if (err)
+		return err;
+
+	return count;
+}
+
+static void damon_sysfs_regions_release(struct kobject *kobj)
+{
+	kfree(container_of(kobj, struct damon_sysfs_regions, kobj));
+}
+
+static struct kobj_attribute damon_sysfs_regions_nr_attr =
+		__ATTR_RW_MODE(nr_regions, 0600);
+
+static struct attribute *damon_sysfs_regions_attrs[] = {
+	&damon_sysfs_regions_nr_attr.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(damon_sysfs_regions);
+
+static const struct kobj_type damon_sysfs_regions_ktype = {
+	.release = damon_sysfs_regions_release,
+	.sysfs_ops = &kobj_sysfs_ops,
+	.default_groups = damon_sysfs_regions_groups,
+};
+
+/*
+ * target directory
+ */
+
+struct damon_sysfs_target {
+	struct kobject kobj;
+	struct damon_sysfs_regions *regions;
+	int pid;
+};
+
+static struct damon_sysfs_target *damon_sysfs_target_alloc(void)
+{
+	return kzalloc(sizeof(struct damon_sysfs_target), GFP_KERNEL);
+}
+
+static int damon_sysfs_target_add_dirs(struct damon_sysfs_target *target)
+{
+	struct damon_sysfs_regions *regions = damon_sysfs_regions_alloc();
+	int err;
+
+	if (!regions)
+		return -ENOMEM;
+
+	err = kobject_init_and_add(&regions->kobj, &damon_sysfs_regions_ktype,
+			&target->kobj, "regions");
+	if (err)
+		kobject_put(&regions->kobj);
+	else
+		target->regions = regions;
+	return err;
+}
+
+static void damon_sysfs_target_rm_dirs(struct damon_sysfs_target *target)
+{
+	damon_sysfs_regions_rm_dirs(target->regions);
+	kobject_put(&target->regions->kobj);
+}
+
+static ssize_t pid_target_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	struct damon_sysfs_target *target = container_of(kobj,
+			struct damon_sysfs_target, kobj);
+
+	return sysfs_emit(buf, "%d\n", target->pid);
+}
+
+static ssize_t pid_target_store(struct kobject *kobj,
+		struct kobj_attribute *attr, const char *buf, size_t count)
+{
+	struct damon_sysfs_target *target = container_of(kobj,
+			struct damon_sysfs_target, kobj);
+	int err = kstrtoint(buf, 0, &target->pid);
+
+	if (err)
+		return -EINVAL;
+	return count;
+}
+
+static void damon_sysfs_target_release(struct kobject *kobj)
+{
+	kfree(container_of(kobj, struct damon_sysfs_target, kobj));
+}
+
+static struct kobj_attribute damon_sysfs_target_pid_attr =
+		__ATTR_RW_MODE(pid_target, 0600);
+
+static struct attribute *damon_sysfs_target_attrs[] = {
+	&damon_sysfs_target_pid_attr.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(damon_sysfs_target);
+
+static const struct kobj_type damon_sysfs_target_ktype = {
+	.release = damon_sysfs_target_release,
+	.sysfs_ops = &kobj_sysfs_ops,
+	.default_groups = damon_sysfs_target_groups,
+};
+
+/*
+ * targets directory
+ */
+
+struct damon_sysfs_targets {
+	struct kobject kobj;
+	struct damon_sysfs_target **targets_arr;
+	int nr;
+};
+
+static struct damon_sysfs_targets *damon_sysfs_targets_alloc(void)
+{
+	return kzalloc(sizeof(struct damon_sysfs_targets), GFP_KERNEL);
+}
+
+static void damon_sysfs_targets_rm_dirs(struct damon_sysfs_targets *targets)
+{
+	struct damon_sysfs_target **targets_arr = targets->targets_arr;
+	int i;
+
+	for (i = 0; i < targets->nr; i++) {
+		damon_sysfs_target_rm_dirs(targets_arr[i]);
+		kobject_put(&targets_arr[i]->kobj);
+	}
+	targets->nr = 0;
+	kfree(targets_arr);
+	targets->targets_arr = NULL;
+}
+
+static int damon_sysfs_targets_add_dirs(struct damon_sysfs_targets *targets,
+		int nr_targets)
+{
+	struct damon_sysfs_target **targets_arr, *target;
+	int err, i;
+
+	damon_sysfs_targets_rm_dirs(targets);
+	if (!nr_targets)
+		return 0;
+
+	targets_arr = kmalloc_array(nr_targets, sizeof(*targets_arr),
+			GFP_KERNEL | __GFP_NOWARN);
+	if (!targets_arr)
+		return -ENOMEM;
+	targets->targets_arr = targets_arr;
+
+	for (i = 0; i < nr_targets; i++) {
+		target = damon_sysfs_target_alloc();
+		if (!target) {
+			damon_sysfs_targets_rm_dirs(targets);
+			return -ENOMEM;
+		}
+
+		err = kobject_init_and_add(&target->kobj,
+				&damon_sysfs_target_ktype, &targets->kobj,
+				"%d", i);
+		if (err)
+			goto out;
+
+		err = damon_sysfs_target_add_dirs(target);
+		if (err)
+			goto out;
+
+		targets_arr[i] = target;
+		targets->nr++;
+	}
+	return 0;
+
+out:
+	damon_sysfs_targets_rm_dirs(targets);
+	kobject_put(&target->kobj);
+	return err;
+}
+
+static ssize_t nr_targets_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	struct damon_sysfs_targets *targets = container_of(kobj,
+			struct damon_sysfs_targets, kobj);
+
+	return sysfs_emit(buf, "%d\n", targets->nr);
+}
+
+static ssize_t nr_targets_store(struct kobject *kobj,
+		struct kobj_attribute *attr, const char *buf, size_t count)
+{
+	struct damon_sysfs_targets *targets;
+	int nr, err = kstrtoint(buf, 0, &nr);
+
+	if (err)
+		return err;
+	if (nr < 0)
+		return -EINVAL;
+
+	targets = container_of(kobj, struct damon_sysfs_targets, kobj);
+
+	if (!mutex_trylock(&damon_sysfs_lock))
+		return -EBUSY;
+	err = damon_sysfs_targets_add_dirs(targets, nr);
+	mutex_unlock(&damon_sysfs_lock);
+	if (err)
+		return err;
+
+	return count;
+}
+
+static void damon_sysfs_targets_release(struct kobject *kobj)
+{
+	kfree(container_of(kobj, struct damon_sysfs_targets, kobj));
+}
+
+static struct kobj_attribute damon_sysfs_targets_nr_attr =
+		__ATTR_RW_MODE(nr_targets, 0600);
+
+static struct attribute *damon_sysfs_targets_attrs[] = {
+	&damon_sysfs_targets_nr_attr.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(damon_sysfs_targets);
+
+static const struct kobj_type damon_sysfs_targets_ktype = {
+	.release = damon_sysfs_targets_release,
+	.sysfs_ops = &kobj_sysfs_ops,
+	.default_groups = damon_sysfs_targets_groups,
+};
+
+/*
+ * intervals directory
+ */
+
+struct damon_sysfs_intervals {
+	struct kobject kobj;
+	unsigned long sample_us;
+	unsigned long aggr_us;
+	unsigned long update_us;
+};
+
+static struct damon_sysfs_intervals *damon_sysfs_intervals_alloc(
+		unsigned long sample_us, unsigned long aggr_us,
+		unsigned long update_us)
+{
+	struct damon_sysfs_intervals *intervals = kmalloc(sizeof(*intervals),
+			GFP_KERNEL);
+
+	if (!intervals)
+		return NULL;
+
+	intervals->kobj = (struct kobject){};
+	intervals->sample_us = sample_us;
+	intervals->aggr_us = aggr_us;
+	intervals->update_us = update_us;
+	return intervals;
+}
+
+static ssize_t sample_us_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	struct damon_sysfs_intervals *intervals = container_of(kobj,
+			struct damon_sysfs_intervals, kobj);
+
+	return sysfs_emit(buf, "%lu\n", intervals->sample_us);
+}
+
+static ssize_t sample_us_store(struct kobject *kobj,
+		struct kobj_attribute *attr, const char *buf, size_t count)
+{
+	struct damon_sysfs_intervals *intervals = container_of(kobj,
+			struct damon_sysfs_intervals, kobj);
+	unsigned long us;
+	int err = kstrtoul(buf, 0, &us);
+
+	if (err)
+		return err;
+
+	intervals->sample_us = us;
+	return count;
+}
+
+static ssize_t aggr_us_show(struct kobject *kobj, struct kobj_attribute *attr,
+		char *buf)
+{
+	struct damon_sysfs_intervals *intervals = container_of(kobj,
+			struct damon_sysfs_intervals, kobj);
+
+	return sysfs_emit(buf, "%lu\n", intervals->aggr_us);
+}
+
+static ssize_t aggr_us_store(struct kobject *kobj, struct kobj_attribute *attr,
+		const char *buf, size_t count)
+{
+	struct damon_sysfs_intervals *intervals = container_of(kobj,
+			struct damon_sysfs_intervals, kobj);
+	unsigned long us;
+	int err = kstrtoul(buf, 0, &us);
+
+	if (err)
+		return err;
+
+	intervals->aggr_us = us;
+	return count;
+}
+
+static ssize_t update_us_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	struct damon_sysfs_intervals *intervals = container_of(kobj,
+			struct damon_sysfs_intervals, kobj);
+
+	return sysfs_emit(buf, "%lu\n", intervals->update_us);
+}
+
+static ssize_t update_us_store(struct kobject *kobj,
+		struct kobj_attribute *attr, const char *buf, size_t count)
+{
+	struct damon_sysfs_intervals *intervals = container_of(kobj,
+			struct damon_sysfs_intervals, kobj);
+	unsigned long us;
+	int err = kstrtoul(buf, 0, &us);
+
+	if (err)
+		return err;
+
+	intervals->update_us = us;
+	return count;
+}
+
+static void damon_sysfs_intervals_release(struct kobject *kobj)
+{
+	kfree(container_of(kobj, struct damon_sysfs_intervals, kobj));
+}
+
+static struct kobj_attribute damon_sysfs_intervals_sample_us_attr =
+		__ATTR_RW_MODE(sample_us, 0600);
+
+static struct kobj_attribute damon_sysfs_intervals_aggr_us_attr =
+		__ATTR_RW_MODE(aggr_us, 0600);
+
+static struct kobj_attribute damon_sysfs_intervals_update_us_attr =
+		__ATTR_RW_MODE(update_us, 0600);
+
+static struct attribute *damon_sysfs_intervals_attrs[] = {
+	&damon_sysfs_intervals_sample_us_attr.attr,
+	&damon_sysfs_intervals_aggr_us_attr.attr,
+	&damon_sysfs_intervals_update_us_attr.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(damon_sysfs_intervals);
+
+static const struct kobj_type damon_sysfs_intervals_ktype = {
+	.release = damon_sysfs_intervals_release,
+	.sysfs_ops = &kobj_sysfs_ops,
+	.default_groups = damon_sysfs_intervals_groups,
+};
+
+/*
+ * monitoring_attrs directory
+ */
+
+struct damon_sysfs_attrs {
+	struct kobject kobj;
+	struct damon_sysfs_intervals *intervals;
+	struct damon_sysfs_ul_range *nr_regions_range;
+};
+
+static struct damon_sysfs_attrs *damon_sysfs_attrs_alloc(void)
+{
+	struct damon_sysfs_attrs *attrs = kmalloc(sizeof(*attrs), GFP_KERNEL);
+
+	if (!attrs)
+		return NULL;
+	attrs->kobj = (struct kobject){};
+	return attrs;
+}
+
+static int damon_sysfs_attrs_add_dirs(struct damon_sysfs_attrs *attrs)
+{
+	struct damon_sysfs_intervals *intervals;
+	struct damon_sysfs_ul_range *nr_regions_range;
+	int err;
+
+	intervals = damon_sysfs_intervals_alloc(5000, 100000, 60000000);
+	if (!intervals)
+		return -ENOMEM;
+
+	err = kobject_init_and_add(&intervals->kobj,
+			&damon_sysfs_intervals_ktype, &attrs->kobj,
+			"intervals");
+	if (err)
+		goto put_intervals_out;
+	attrs->intervals = intervals;
+
+	nr_regions_range = damon_sysfs_ul_range_alloc(10, 1000);
+	if (!nr_regions_range) {
+		err = -ENOMEM;
+		goto put_intervals_out;
+	}
+
+	err = kobject_init_and_add(&nr_regions_range->kobj,
+			&damon_sysfs_ul_range_ktype, &attrs->kobj,
+			"nr_regions");
+	if (err)
+		goto put_nr_regions_intervals_out;
+	attrs->nr_regions_range = nr_regions_range;
+	return 0;
+
+put_nr_regions_intervals_out:
+	kobject_put(&nr_regions_range->kobj);
+	attrs->nr_regions_range = NULL;
+put_intervals_out:
+	kobject_put(&intervals->kobj);
+	attrs->intervals = NULL;
+	return err;
+}
+
+static void damon_sysfs_attrs_rm_dirs(struct damon_sysfs_attrs *attrs)
+{
+	kobject_put(&attrs->nr_regions_range->kobj);
+	kobject_put(&attrs->intervals->kobj);
+}
+
+static void damon_sysfs_attrs_release(struct kobject *kobj)
+{
+	kfree(container_of(kobj, struct damon_sysfs_attrs, kobj));
+}
+
+static struct attribute *damon_sysfs_attrs_attrs[] = {
+	NULL,
+};
+ATTRIBUTE_GROUPS(damon_sysfs_attrs);
+
+static const struct kobj_type damon_sysfs_attrs_ktype = {
+	.release = damon_sysfs_attrs_release,
+	.sysfs_ops = &kobj_sysfs_ops,
+	.default_groups = damon_sysfs_attrs_groups,
+};
+
+/*
+ * context directory
+ */
+
+/* This should match with enum damon_ops_id */
+static const char * const damon_sysfs_ops_strs[] = {
+	"vaddr",
+	"fvaddr",
+	"paddr",
+};
+
+struct damon_sysfs_context {
+	struct kobject kobj;
+	enum damon_ops_id ops_id;
+	struct damon_sysfs_attrs *attrs;
+	struct damon_sysfs_targets *targets;
+	struct damon_sysfs_schemes *schemes;
+};
+
+static struct damon_sysfs_context *damon_sysfs_context_alloc(
+		enum damon_ops_id ops_id)
+{
+	struct damon_sysfs_context *context = kmalloc(sizeof(*context),
+				GFP_KERNEL);
+
+	if (!context)
+		return NULL;
+	context->kobj = (struct kobject){};
+	context->ops_id = ops_id;
+	return context;
+}
+
+static int damon_sysfs_context_set_attrs(struct damon_sysfs_context *context)
+{
+	struct damon_sysfs_attrs *attrs = damon_sysfs_attrs_alloc();
+	int err;
+
+	if (!attrs)
+		return -ENOMEM;
+	err = kobject_init_and_add(&attrs->kobj, &damon_sysfs_attrs_ktype,
+			&context->kobj, "monitoring_attrs");
+	if (err)
+		goto out;
+	err = damon_sysfs_attrs_add_dirs(attrs);
+	if (err)
+		goto out;
+	context->attrs = attrs;
+	return 0;
+
+out:
+	kobject_put(&attrs->kobj);
+	return err;
+}
+
+static int damon_sysfs_context_set_targets(struct damon_sysfs_context *context)
+{
+	struct damon_sysfs_targets *targets = damon_sysfs_targets_alloc();
+	int err;
+
+	if (!targets)
+		return -ENOMEM;
+	err = kobject_init_and_add(&targets->kobj, &damon_sysfs_targets_ktype,
+			&context->kobj, "targets");
+	if (err) {
+		kobject_put(&targets->kobj);
+		return err;
+	}
+	context->targets = targets;
+	return 0;
+}
+
+static int damon_sysfs_context_set_schemes(struct damon_sysfs_context *context)
+{
+	struct damon_sysfs_schemes *schemes = damon_sysfs_schemes_alloc();
+	int err;
+
+	if (!schemes)
+		return -ENOMEM;
+	err = kobject_init_and_add(&schemes->kobj, &damon_sysfs_schemes_ktype,
+			&context->kobj, "schemes");
+	if (err) {
+		kobject_put(&schemes->kobj);
+		return err;
+	}
+	context->schemes = schemes;
+	return 0;
+}
+
+static int damon_sysfs_context_add_dirs(struct damon_sysfs_context *context)
+{
+	int err;
+
+	err = damon_sysfs_context_set_attrs(context);
+	if (err)
+		return err;
+
+	err = damon_sysfs_context_set_targets(context);
+	if (err)
+		goto put_attrs_out;
+
+	err = damon_sysfs_context_set_schemes(context);
+	if (err)
+		goto put_targets_attrs_out;
+	return 0;
+
+put_targets_attrs_out:
+	kobject_put(&context->targets->kobj);
+	context->targets = NULL;
+put_attrs_out:
+	kobject_put(&context->attrs->kobj);
+	context->attrs = NULL;
+	return err;
+}
+
+static void damon_sysfs_context_rm_dirs(struct damon_sysfs_context *context)
+{
+	damon_sysfs_attrs_rm_dirs(context->attrs);
+	kobject_put(&context->attrs->kobj);
+	damon_sysfs_targets_rm_dirs(context->targets);
+	kobject_put(&context->targets->kobj);
+	damon_sysfs_schemes_rm_dirs(context->schemes);
+	kobject_put(&context->schemes->kobj);
+}
+
+static ssize_t avail_operations_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	enum damon_ops_id id;
+	int len = 0;
+
+	for (id = 0; id < NR_DAMON_OPS; id++) {
+		if (!damon_is_registered_ops(id))
+			continue;
+		len += sysfs_emit_at(buf, len, "%s\n",
+				damon_sysfs_ops_strs[id]);
+	}
+	return len;
+}
+
+static ssize_t operations_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	struct damon_sysfs_context *context = container_of(kobj,
+			struct damon_sysfs_context, kobj);
+
+	return sysfs_emit(buf, "%s\n", damon_sysfs_ops_strs[context->ops_id]);
+}
+
+static ssize_t operations_store(struct kobject *kobj,
+		struct kobj_attribute *attr, const char *buf, size_t count)
+{
+	struct damon_sysfs_context *context = container_of(kobj,
+			struct damon_sysfs_context, kobj);
+	enum damon_ops_id id;
+
+	for (id = 0; id < NR_DAMON_OPS; id++) {
+		if (sysfs_streq(buf, damon_sysfs_ops_strs[id])) {
+			context->ops_id = id;
+			return count;
+		}
+	}
+	return -EINVAL;
+}
+
+static void damon_sysfs_context_release(struct kobject *kobj)
+{
+	kfree(container_of(kobj, struct damon_sysfs_context, kobj));
+}
+
+static struct kobj_attribute damon_sysfs_context_avail_operations_attr =
+		__ATTR_RO_MODE(avail_operations, 0400);
+
+static struct kobj_attribute damon_sysfs_context_operations_attr =
+		__ATTR_RW_MODE(operations, 0600);
+
+static struct attribute *damon_sysfs_context_attrs[] = {
+	&damon_sysfs_context_avail_operations_attr.attr,
+	&damon_sysfs_context_operations_attr.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(damon_sysfs_context);
+
+static const struct kobj_type damon_sysfs_context_ktype = {
+	.release = damon_sysfs_context_release,
+	.sysfs_ops = &kobj_sysfs_ops,
+	.default_groups = damon_sysfs_context_groups,
+};
+
+/*
+ * contexts directory
+ */
+
+struct damon_sysfs_contexts {
+	struct kobject kobj;
+	struct damon_sysfs_context **contexts_arr;
+	int nr;
+};
+
+static struct damon_sysfs_contexts *damon_sysfs_contexts_alloc(void)
+{
+	return kzalloc(sizeof(struct damon_sysfs_contexts), GFP_KERNEL);
+}
+
+static void damon_sysfs_contexts_rm_dirs(struct damon_sysfs_contexts *contexts)
+{
+	struct damon_sysfs_context **contexts_arr = contexts->contexts_arr;
+	int i;
+
+	for (i = 0; i < contexts->nr; i++) {
+		damon_sysfs_context_rm_dirs(contexts_arr[i]);
+		kobject_put(&contexts_arr[i]->kobj);
+	}
+	contexts->nr = 0;
+	kfree(contexts_arr);
+	contexts->contexts_arr = NULL;
+}
+
+static int damon_sysfs_contexts_add_dirs(struct damon_sysfs_contexts *contexts,
+		int nr_contexts)
+{
+	struct damon_sysfs_context **contexts_arr, *context;
+	int err, i;
+
+	damon_sysfs_contexts_rm_dirs(contexts);
+	if (!nr_contexts)
+		return 0;
+
+	contexts_arr = kmalloc_array(nr_contexts, sizeof(*contexts_arr),
+			GFP_KERNEL | __GFP_NOWARN);
+	if (!contexts_arr)
+		return -ENOMEM;
+	contexts->contexts_arr = contexts_arr;
+
+	for (i = 0; i < nr_contexts; i++) {
+		context = damon_sysfs_context_alloc(DAMON_OPS_VADDR);
+		if (!context) {
+			damon_sysfs_contexts_rm_dirs(contexts);
+			return -ENOMEM;
+		}
+
+		err = kobject_init_and_add(&context->kobj,
+				&damon_sysfs_context_ktype, &contexts->kobj,
+				"%d", i);
+		if (err)
+			goto out;
+
+		err = damon_sysfs_context_add_dirs(context);
+		if (err)
+			goto out;
+
+		contexts_arr[i] = context;
+		contexts->nr++;
+	}
+	return 0;
+
+out:
+	damon_sysfs_contexts_rm_dirs(contexts);
+	kobject_put(&context->kobj);
+	return err;
+}
+
+static ssize_t nr_contexts_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	struct damon_sysfs_contexts *contexts = container_of(kobj,
+			struct damon_sysfs_contexts, kobj);
+
+	return sysfs_emit(buf, "%d\n", contexts->nr);
+}
+
+static ssize_t nr_contexts_store(struct kobject *kobj,
+		struct kobj_attribute *attr, const char *buf, size_t count)
+{
+	struct damon_sysfs_contexts *contexts;
+	int nr, err;
+
+	err = kstrtoint(buf, 0, &nr);
+	if (err)
+		return err;
+	/* TODO: support multiple contexts per kdamond */
+	if (nr < 0 || 1 < nr)
+		return -EINVAL;
+
+	contexts = container_of(kobj, struct damon_sysfs_contexts, kobj);
+	if (!mutex_trylock(&damon_sysfs_lock))
+		return -EBUSY;
+	err = damon_sysfs_contexts_add_dirs(contexts, nr);
+	mutex_unlock(&damon_sysfs_lock);
+	if (err)
+		return err;
+
+	return count;
+}
+
+static void damon_sysfs_contexts_release(struct kobject *kobj)
+{
+	kfree(container_of(kobj, struct damon_sysfs_contexts, kobj));
+}
+
+static struct kobj_attribute damon_sysfs_contexts_nr_attr
+		= __ATTR_RW_MODE(nr_contexts, 0600);
+
+static struct attribute *damon_sysfs_contexts_attrs[] = {
+	&damon_sysfs_contexts_nr_attr.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(damon_sysfs_contexts);
+
+static const struct kobj_type damon_sysfs_contexts_ktype = {
+	.release = damon_sysfs_contexts_release,
+	.sysfs_ops = &kobj_sysfs_ops,
+	.default_groups = damon_sysfs_contexts_groups,
+};
+
+/*
+ * kdamond directory
+ */
+
+struct damon_sysfs_kdamond {
+	struct kobject kobj;
+	struct damon_sysfs_contexts *contexts;
+	struct damon_ctx *damon_ctx;
+};
+
+static struct damon_sysfs_kdamond *damon_sysfs_kdamond_alloc(void)
+{
+	return kzalloc(sizeof(struct damon_sysfs_kdamond), GFP_KERNEL);
+}
+
+static int damon_sysfs_kdamond_add_dirs(struct damon_sysfs_kdamond *kdamond)
+{
+	struct damon_sysfs_contexts *contexts;
+	int err;
+
+	contexts = damon_sysfs_contexts_alloc();
+	if (!contexts)
+		return -ENOMEM;
+
+	err = kobject_init_and_add(&contexts->kobj,
+			&damon_sysfs_contexts_ktype, &kdamond->kobj,
+			"contexts");
+	if (err) {
+		kobject_put(&contexts->kobj);
+		return err;
+	}
+	kdamond->contexts = contexts;
+
+	return err;
+}
+
+static void damon_sysfs_kdamond_rm_dirs(struct damon_sysfs_kdamond *kdamond)
+{
+	damon_sysfs_contexts_rm_dirs(kdamond->contexts);
+	kobject_put(&kdamond->contexts->kobj);
+}
+
+static bool damon_sysfs_ctx_running(struct damon_ctx *ctx)
+{
+	bool running;
+
+	mutex_lock(&ctx->kdamond_lock);
+	running = ctx->kdamond != NULL;
+	mutex_unlock(&ctx->kdamond_lock);
+	return running;
+}
+
+/*
+ * enum damon_sysfs_cmd - Commands for a specific kdamond.
+ */
+enum damon_sysfs_cmd {
+	/* @DAMON_SYSFS_CMD_ON: Turn the kdamond on. */
+	DAMON_SYSFS_CMD_ON,
+	/* @DAMON_SYSFS_CMD_OFF: Turn the kdamond off. */
+	DAMON_SYSFS_CMD_OFF,
+	/* @DAMON_SYSFS_CMD_COMMIT: Update kdamond inputs. */
+	DAMON_SYSFS_CMD_COMMIT,
+	/*
+	 * @DAMON_SYSFS_CMD_UPDATE_SCHEMES_STATS: Update scheme stats sysfs
+	 * files.
+	 */
+	DAMON_SYSFS_CMD_UPDATE_SCHEMES_STATS,
+	/*
+	 * @DAMON_SYSFS_CMD_UPDATE_SCHEMES_TRIED_BYTES: Update
+	 * tried_regions/total_bytes sysfs files for each scheme.
+	 */
+	DAMON_SYSFS_CMD_UPDATE_SCHEMES_TRIED_BYTES,
+	/*
+	 * @DAMON_SYSFS_CMD_UPDATE_SCHEMES_TRIED_REGIONS: Update schemes tried
+	 * regions
+	 */
+	DAMON_SYSFS_CMD_UPDATE_SCHEMES_TRIED_REGIONS,
+	/*
+	 * @DAMON_SYSFS_CMD_CLEAR_SCHEMES_TRIED_REGIONS: Clear schemes tried
+	 * regions
+	 */
+	DAMON_SYSFS_CMD_CLEAR_SCHEMES_TRIED_REGIONS,
+	/*
+	 * @NR_DAMON_SYSFS_CMDS: Total number of DAMON sysfs commands.
+	 */
+	NR_DAMON_SYSFS_CMDS,
+};
+
+/* Should match with enum damon_sysfs_cmd */
+static const char * const damon_sysfs_cmd_strs[] = {
+	"on",
+	"off",
+	"commit",
+	"update_schemes_stats",
+	"update_schemes_tried_bytes",
+	"update_schemes_tried_regions",
+	"clear_schemes_tried_regions",
+};
+
+/*
+ * struct damon_sysfs_cmd_request - A request to the DAMON callback.
+ * @cmd:	The command that needs to be handled by the callback.
+ * @kdamond:	The kobject wrapper that associated to the kdamond thread.
+ *
+ * This structure represents a sysfs command request that need to access some
+ * DAMON context-internal data.  Because DAMON context-internal data can be
+ * safely accessed from DAMON callbacks without additional synchronization, the
+ * request will be handled by the DAMON callback.  None-``NULL`` @kdamond means
+ * the request is valid.
+ */
+struct damon_sysfs_cmd_request {
+	enum damon_sysfs_cmd cmd;
+	struct damon_sysfs_kdamond *kdamond;
+};
+
+/* Current DAMON callback request.  Protected by damon_sysfs_lock. */
+static struct damon_sysfs_cmd_request damon_sysfs_cmd_request;
+
+static ssize_t state_show(struct kobject *kobj, struct kobj_attribute *attr,
+		char *buf)
+{
+	struct damon_sysfs_kdamond *kdamond = container_of(kobj,
+			struct damon_sysfs_kdamond, kobj);
+	struct damon_ctx *ctx = kdamond->damon_ctx;
+	bool running;
+
+	if (!ctx)
+		running = false;
+	else
+		running = damon_sysfs_ctx_running(ctx);
+
+	return sysfs_emit(buf, "%s\n", running ?
+			damon_sysfs_cmd_strs[DAMON_SYSFS_CMD_ON] :
+			damon_sysfs_cmd_strs[DAMON_SYSFS_CMD_OFF]);
+}
+
+static int damon_sysfs_set_attrs(struct damon_ctx *ctx,
+		struct damon_sysfs_attrs *sys_attrs)
+{
+	struct damon_sysfs_intervals *sys_intervals = sys_attrs->intervals;
+	struct damon_sysfs_ul_range *sys_nr_regions =
+		sys_attrs->nr_regions_range;
+	struct damon_attrs attrs = {
+		.sample_interval = sys_intervals->sample_us,
+		.aggr_interval = sys_intervals->aggr_us,
+		.ops_update_interval = sys_intervals->update_us,
+		.min_nr_regions = sys_nr_regions->min,
+		.max_nr_regions = sys_nr_regions->max,
+	};
+	return damon_set_attrs(ctx, &attrs);
+}
+
+static void damon_sysfs_destroy_targets(struct damon_ctx *ctx)
+{
+	struct damon_target *t, *next;
+	bool has_pid = damon_target_has_pid(ctx);
+
+	damon_for_each_target_safe(t, next, ctx) {
+		if (has_pid)
+			put_pid(t->pid);
+		damon_destroy_target(t);
+	}
+}
+
+static int damon_sysfs_set_regions(struct damon_target *t,
+		struct damon_sysfs_regions *sysfs_regions)
+{
+	struct damon_addr_range *ranges = kmalloc_array(sysfs_regions->nr,
+			sizeof(*ranges), GFP_KERNEL | __GFP_NOWARN);
+	int i, err = -EINVAL;
+
+	if (!ranges)
+		return -ENOMEM;
+	for (i = 0; i < sysfs_regions->nr; i++) {
+		struct damon_sysfs_region *sys_region =
+			sysfs_regions->regions_arr[i];
+
+		if (sys_region->ar.start > sys_region->ar.end)
+			goto out;
+
+		ranges[i].start = sys_region->ar.start;
+		ranges[i].end = sys_region->ar.end;
+		if (i == 0)
+			continue;
+		if (ranges[i - 1].end > ranges[i].start)
+			goto out;
+	}
+	err = damon_set_regions(t, ranges, sysfs_regions->nr);
+out:
+	kfree(ranges);
+	return err;
+
+}
+
+static int damon_sysfs_add_target(struct damon_sysfs_target *sys_target,
+		struct damon_ctx *ctx)
+{
+	struct damon_target *t = damon_new_target();
+	int err = -EINVAL;
+
+	if (!t)
+		return -ENOMEM;
+	damon_add_target(ctx, t);
+	if (damon_target_has_pid(ctx)) {
+		t->pid = find_get_pid(sys_target->pid);
+		if (!t->pid)
+			goto destroy_targets_out;
+	}
+	err = damon_sysfs_set_regions(t, sys_target->regions);
+	if (err)
+		goto destroy_targets_out;
+	return 0;
+
+destroy_targets_out:
+	damon_sysfs_destroy_targets(ctx);
+	return err;
+}
+
+static int damon_sysfs_update_target_pid(struct damon_target *target, int pid)
+{
+	struct pid *pid_new;
+
+	pid_new = find_get_pid(pid);
+	if (!pid_new)
+		return -EINVAL;
+
+	if (pid_new == target->pid) {
+		put_pid(pid_new);
+		return 0;
+	}
+
+	put_pid(target->pid);
+	target->pid = pid_new;
+	return 0;
+}
+
+static int damon_sysfs_update_target(struct damon_target *target,
+		struct damon_ctx *ctx,
+		struct damon_sysfs_target *sys_target)
+{
+	int err = 0;
+
+	if (damon_target_has_pid(ctx)) {
+		err = damon_sysfs_update_target_pid(target, sys_target->pid);
+		if (err)
+			return err;
+	}
+
+	/*
+	 * Do monitoring target region boundary update only if one or more
+	 * regions are set by the user.  This is for keeping current monitoring
+	 * target results and range easier, especially for dynamic monitoring
+	 * target regions update ops like 'vaddr'.
+	 */
+	if (sys_target->regions->nr)
+		err = damon_sysfs_set_regions(target, sys_target->regions);
+	return err;
+}
+
+static int damon_sysfs_set_targets(struct damon_ctx *ctx,
+		struct damon_sysfs_targets *sysfs_targets)
+{
+	struct damon_target *t, *next;
+	int i = 0, err;
+
+	/* Multiple physical address space monitoring targets makes no sense */
+	if (ctx->ops.id == DAMON_OPS_PADDR && sysfs_targets->nr > 1)
+		return -EINVAL;
+
+	damon_for_each_target_safe(t, next, ctx) {
+		if (i < sysfs_targets->nr) {
+			err = damon_sysfs_update_target(t, ctx,
+					sysfs_targets->targets_arr[i]);
+			if (err)
+				return err;
+		} else {
+			if (damon_target_has_pid(ctx))
+				put_pid(t->pid);
+			damon_destroy_target(t);
+		}
+		i++;
+	}
+
+	for (; i < sysfs_targets->nr; i++) {
+		struct damon_sysfs_target *st = sysfs_targets->targets_arr[i];
+
+		err = damon_sysfs_add_target(st, ctx);
+		if (err)
+			return err;
+	}
+	return 0;
+}
+
+static bool damon_sysfs_schemes_regions_updating;
+
+static void damon_sysfs_before_terminate(struct damon_ctx *ctx)
+{
+	struct damon_target *t, *next;
+	struct damon_sysfs_kdamond *kdamond;
+	enum damon_sysfs_cmd cmd;
+
+	/* damon_sysfs_schemes_update_regions_stop() might not yet called */
+	kdamond = damon_sysfs_cmd_request.kdamond;
+	cmd = damon_sysfs_cmd_request.cmd;
+	if (kdamond && ctx == kdamond->damon_ctx &&
+			(cmd == DAMON_SYSFS_CMD_UPDATE_SCHEMES_TRIED_REGIONS ||
+			 cmd == DAMON_SYSFS_CMD_UPDATE_SCHEMES_TRIED_BYTES) &&
+			damon_sysfs_schemes_regions_updating) {
+		damon_sysfs_schemes_update_regions_stop(ctx);
+		damon_sysfs_schemes_regions_updating = false;
+		mutex_unlock(&damon_sysfs_lock);
+	}
+
+	if (!damon_target_has_pid(ctx))
+		return;
+
+	mutex_lock(&ctx->kdamond_lock);
+	damon_for_each_target_safe(t, next, ctx) {
+		put_pid(t->pid);
+		damon_destroy_target(t);
+	}
+	mutex_unlock(&ctx->kdamond_lock);
+}
+
+/*
+ * damon_sysfs_upd_schemes_stats() - Update schemes stats sysfs files.
+ * @kdamond:	The kobject wrapper that associated to the kdamond thread.
+ *
+ * This function reads the schemes stats of specific kdamond and update the
+ * related values for sysfs files.  This function should be called from DAMON
+ * callbacks while holding ``damon_syfs_lock``, to safely access the DAMON
+ * contexts-internal data and DAMON sysfs variables.
+ */
+static int damon_sysfs_upd_schemes_stats(struct damon_sysfs_kdamond *kdamond)
+{
+	struct damon_ctx *ctx = kdamond->damon_ctx;
+
+	if (!ctx)
+		return -EINVAL;
+	damon_sysfs_schemes_update_stats(
+			kdamond->contexts->contexts_arr[0]->schemes, ctx);
+	return 0;
+}
+
+static int damon_sysfs_upd_schemes_regions_start(
+		struct damon_sysfs_kdamond *kdamond, bool total_bytes_only)
+{
+	struct damon_ctx *ctx = kdamond->damon_ctx;
+
+	if (!ctx)
+		return -EINVAL;
+	return damon_sysfs_schemes_update_regions_start(
+			kdamond->contexts->contexts_arr[0]->schemes, ctx,
+			total_bytes_only);
+}
+
+static int damon_sysfs_upd_schemes_regions_stop(
+		struct damon_sysfs_kdamond *kdamond)
+{
+	struct damon_ctx *ctx = kdamond->damon_ctx;
+
+	if (!ctx)
+		return -EINVAL;
+	return damon_sysfs_schemes_update_regions_stop(ctx);
+}
+
+static int damon_sysfs_clear_schemes_regions(
+		struct damon_sysfs_kdamond *kdamond)
+{
+	struct damon_ctx *ctx = kdamond->damon_ctx;
+
+	if (!ctx)
+		return -EINVAL;
+	return damon_sysfs_schemes_clear_regions(
+			kdamond->contexts->contexts_arr[0]->schemes, ctx);
+}
+
+static inline bool damon_sysfs_kdamond_running(
+		struct damon_sysfs_kdamond *kdamond)
+{
+	return kdamond->damon_ctx &&
+		damon_sysfs_ctx_running(kdamond->damon_ctx);
+}
+
+static int damon_sysfs_apply_inputs(struct damon_ctx *ctx,
+		struct damon_sysfs_context *sys_ctx)
+{
+	int err;
+
+	err = damon_select_ops(ctx, sys_ctx->ops_id);
+	if (err)
+		return err;
+	err = damon_sysfs_set_attrs(ctx, sys_ctx->attrs);
+	if (err)
+		return err;
+	err = damon_sysfs_set_targets(ctx, sys_ctx->targets);
+	if (err)
+		return err;
+	return damon_sysfs_set_schemes(ctx, sys_ctx->schemes);
+}
+
+/*
+ * damon_sysfs_commit_input() - Commit user inputs to a running kdamond.
+ * @kdamond:	The kobject wrapper for the associated kdamond.
+ *
+ * If the sysfs input is wrong, the kdamond will be terminated.
+ */
+static int damon_sysfs_commit_input(struct damon_sysfs_kdamond *kdamond)
+{
+	if (!damon_sysfs_kdamond_running(kdamond))
+		return -EINVAL;
+	/* TODO: Support multiple contexts per kdamond */
+	if (kdamond->contexts->nr != 1)
+		return -EINVAL;
+
+	return damon_sysfs_apply_inputs(kdamond->damon_ctx,
+			kdamond->contexts->contexts_arr[0]);
+}
+
+/*
+ * damon_sysfs_cmd_request_callback() - DAMON callback for handling requests.
+ * @c:	The DAMON context of the callback.
+ *
+ * This function is periodically called back from the kdamond thread for @c.
+ * Then, it checks if there is a waiting DAMON sysfs request and handles it.
+ */
+static int damon_sysfs_cmd_request_callback(struct damon_ctx *c)
+{
+	struct damon_sysfs_kdamond *kdamond;
+	bool total_bytes_only = false;
+	int err = 0;
+
+	/* avoid deadlock due to concurrent state_store('off') */
+	if (!damon_sysfs_schemes_regions_updating &&
+			!mutex_trylock(&damon_sysfs_lock))
+		return 0;
+	kdamond = damon_sysfs_cmd_request.kdamond;
+	if (!kdamond || kdamond->damon_ctx != c)
+		goto out;
+	switch (damon_sysfs_cmd_request.cmd) {
+	case DAMON_SYSFS_CMD_UPDATE_SCHEMES_STATS:
+		err = damon_sysfs_upd_schemes_stats(kdamond);
+		break;
+	case DAMON_SYSFS_CMD_COMMIT:
+		err = damon_sysfs_commit_input(kdamond);
+		break;
+	case DAMON_SYSFS_CMD_UPDATE_SCHEMES_TRIED_BYTES:
+		total_bytes_only = true;
+		fallthrough;
+	case DAMON_SYSFS_CMD_UPDATE_SCHEMES_TRIED_REGIONS:
+		if (!damon_sysfs_schemes_regions_updating) {
+			err = damon_sysfs_upd_schemes_regions_start(kdamond,
+					total_bytes_only);
+			if (!err) {
+				damon_sysfs_schemes_regions_updating = true;
+				goto keep_lock_out;
+			}
+		} else {
+			err = damon_sysfs_upd_schemes_regions_stop(kdamond);
+			damon_sysfs_schemes_regions_updating = false;
+		}
+		break;
+	case DAMON_SYSFS_CMD_CLEAR_SCHEMES_TRIED_REGIONS:
+		err = damon_sysfs_clear_schemes_regions(kdamond);
+		break;
+	default:
+		break;
+	}
+	/* Mark the request as invalid now. */
+	damon_sysfs_cmd_request.kdamond = NULL;
+out:
+	if (!damon_sysfs_schemes_regions_updating)
+		mutex_unlock(&damon_sysfs_lock);
+keep_lock_out:
+	return err;
+}
+
+static struct damon_ctx *damon_sysfs_build_ctx(
+		struct damon_sysfs_context *sys_ctx)
+{
+	struct damon_ctx *ctx = damon_new_ctx();
+	int err;
+
+	if (!ctx)
+		return ERR_PTR(-ENOMEM);
+
+	err = damon_sysfs_apply_inputs(ctx, sys_ctx);
+	if (err) {
+		damon_destroy_ctx(ctx);
+		return ERR_PTR(err);
+	}
+
+	ctx->callback.after_wmarks_check = damon_sysfs_cmd_request_callback;
+	ctx->callback.after_aggregation = damon_sysfs_cmd_request_callback;
+	ctx->callback.before_terminate = damon_sysfs_before_terminate;
+	return ctx;
+}
+
+static int damon_sysfs_turn_damon_on(struct damon_sysfs_kdamond *kdamond)
+{
+	struct damon_ctx *ctx;
+	int err;
+
+	if (damon_sysfs_kdamond_running(kdamond))
+		return -EBUSY;
+	if (damon_sysfs_cmd_request.kdamond == kdamond)
+		return -EBUSY;
+	/* TODO: support multiple contexts per kdamond */
+	if (kdamond->contexts->nr != 1)
+		return -EINVAL;
+
+	if (kdamond->damon_ctx)
+		damon_destroy_ctx(kdamond->damon_ctx);
+	kdamond->damon_ctx = NULL;
+
+	ctx = damon_sysfs_build_ctx(kdamond->contexts->contexts_arr[0]);
+	if (IS_ERR(ctx))
+		return PTR_ERR(ctx);
+	err = damon_start(&ctx, 1, false);
+	if (err) {
+		damon_destroy_ctx(ctx);
+		return err;
+	}
+	kdamond->damon_ctx = ctx;
+	return err;
+}
+
+static int damon_sysfs_turn_damon_off(struct damon_sysfs_kdamond *kdamond)
+{
+	if (!kdamond->damon_ctx)
+		return -EINVAL;
+	return damon_stop(&kdamond->damon_ctx, 1);
+	/*
+	 * To allow users show final monitoring results of already turned-off
+	 * DAMON, we free kdamond->damon_ctx in next
+	 * damon_sysfs_turn_damon_on(), or kdamonds_nr_store()
+	 */
+}
+
+/*
+ * damon_sysfs_handle_cmd() - Handle a command for a specific kdamond.
+ * @cmd:	The command to handle.
+ * @kdamond:	The kobject wrapper for the associated kdamond.
+ *
+ * This function handles a DAMON sysfs command for a kdamond.  For commands
+ * that need to access running DAMON context-internal data, it requests
+ * handling of the command to the DAMON callback
+ * (@damon_sysfs_cmd_request_callback()) and wait until it is properly handled,
+ * or the context is completed.
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+static int damon_sysfs_handle_cmd(enum damon_sysfs_cmd cmd,
+		struct damon_sysfs_kdamond *kdamond)
+{
+	bool need_wait = true;
+
+	/* Handle commands that doesn't access DAMON context-internal data */
+	switch (cmd) {
+	case DAMON_SYSFS_CMD_ON:
+		return damon_sysfs_turn_damon_on(kdamond);
+	case DAMON_SYSFS_CMD_OFF:
+		return damon_sysfs_turn_damon_off(kdamond);
+	default:
+		break;
+	}
+
+	/* Pass the command to DAMON callback for safe DAMON context access */
+	if (damon_sysfs_cmd_request.kdamond)
+		return -EBUSY;
+	if (!damon_sysfs_kdamond_running(kdamond))
+		return -EINVAL;
+	damon_sysfs_cmd_request.cmd = cmd;
+	damon_sysfs_cmd_request.kdamond = kdamond;
+
+	/*
+	 * wait until damon_sysfs_cmd_request_callback() handles the request
+	 * from kdamond context
+	 */
+	mutex_unlock(&damon_sysfs_lock);
+	while (need_wait) {
+		schedule_timeout_idle(msecs_to_jiffies(100));
+		if (!mutex_trylock(&damon_sysfs_lock))
+			continue;
+		if (!damon_sysfs_cmd_request.kdamond) {
+			/* damon_sysfs_cmd_request_callback() handled */
+			need_wait = false;
+		} else if (!damon_sysfs_kdamond_running(kdamond)) {
+			/* kdamond has already finished */
+			need_wait = false;
+			damon_sysfs_cmd_request.kdamond = NULL;
+		}
+		mutex_unlock(&damon_sysfs_lock);
+	}
+	mutex_lock(&damon_sysfs_lock);
+	return 0;
+}
+
+static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
+		const char *buf, size_t count)
+{
+	struct damon_sysfs_kdamond *kdamond = container_of(kobj,
+			struct damon_sysfs_kdamond, kobj);
+	enum damon_sysfs_cmd cmd;
+	ssize_t ret = -EINVAL;
+
+	if (!mutex_trylock(&damon_sysfs_lock))
+		return -EBUSY;
+	for (cmd = 0; cmd < NR_DAMON_SYSFS_CMDS; cmd++) {
+		if (sysfs_streq(buf, damon_sysfs_cmd_strs[cmd])) {
+			ret = damon_sysfs_handle_cmd(cmd, kdamond);
+			break;
+		}
+	}
+	mutex_unlock(&damon_sysfs_lock);
+	if (!ret)
+		ret = count;
+	return ret;
+}
+
+static ssize_t pid_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	struct damon_sysfs_kdamond *kdamond = container_of(kobj,
+			struct damon_sysfs_kdamond, kobj);
+	struct damon_ctx *ctx;
+	int pid = -1;
+
+	if (!mutex_trylock(&damon_sysfs_lock))
+		return -EBUSY;
+	ctx = kdamond->damon_ctx;
+	if (!ctx)
+		goto out;
+
+	mutex_lock(&ctx->kdamond_lock);
+	if (ctx->kdamond)
+		pid = ctx->kdamond->pid;
+	mutex_unlock(&ctx->kdamond_lock);
+out:
+	mutex_unlock(&damon_sysfs_lock);
+	return sysfs_emit(buf, "%d\n", pid);
+}
+
+static void damon_sysfs_kdamond_release(struct kobject *kobj)
+{
+	struct damon_sysfs_kdamond *kdamond = container_of(kobj,
+			struct damon_sysfs_kdamond, kobj);
+
+	if (kdamond->damon_ctx)
+		damon_destroy_ctx(kdamond->damon_ctx);
+	kfree(kdamond);
+}
+
+static struct kobj_attribute damon_sysfs_kdamond_state_attr =
+		__ATTR_RW_MODE(state, 0600);
+
+static struct kobj_attribute damon_sysfs_kdamond_pid_attr =
+		__ATTR_RO_MODE(pid, 0400);
+
+static struct attribute *damon_sysfs_kdamond_attrs[] = {
+	&damon_sysfs_kdamond_state_attr.attr,
+	&damon_sysfs_kdamond_pid_attr.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(damon_sysfs_kdamond);
+
+static const struct kobj_type damon_sysfs_kdamond_ktype = {
+	.release = damon_sysfs_kdamond_release,
+	.sysfs_ops = &kobj_sysfs_ops,
+	.default_groups = damon_sysfs_kdamond_groups,
+};
+
+/*
+ * kdamonds directory
+ */
+
+struct damon_sysfs_kdamonds {
+	struct kobject kobj;
+	struct damon_sysfs_kdamond **kdamonds_arr;
+	int nr;
+};
+
+static struct damon_sysfs_kdamonds *damon_sysfs_kdamonds_alloc(void)
+{
+	return kzalloc(sizeof(struct damon_sysfs_kdamonds), GFP_KERNEL);
+}
+
+static void damon_sysfs_kdamonds_rm_dirs(struct damon_sysfs_kdamonds *kdamonds)
+{
+	struct damon_sysfs_kdamond **kdamonds_arr = kdamonds->kdamonds_arr;
+	int i;
+
+	for (i = 0; i < kdamonds->nr; i++) {
+		damon_sysfs_kdamond_rm_dirs(kdamonds_arr[i]);
+		kobject_put(&kdamonds_arr[i]->kobj);
+	}
+	kdamonds->nr = 0;
+	kfree(kdamonds_arr);
+	kdamonds->kdamonds_arr = NULL;
+}
+
+static bool damon_sysfs_kdamonds_busy(struct damon_sysfs_kdamond **kdamonds,
+		int nr_kdamonds)
+{
+	int i;
+
+	for (i = 0; i < nr_kdamonds; i++) {
+		if (damon_sysfs_kdamond_running(kdamonds[i]) ||
+		    damon_sysfs_cmd_request.kdamond == kdamonds[i])
+			return true;
+	}
+
+	return false;
+}
+
+static int damon_sysfs_kdamonds_add_dirs(struct damon_sysfs_kdamonds *kdamonds,
+		int nr_kdamonds)
+{
+	struct damon_sysfs_kdamond **kdamonds_arr, *kdamond;
+	int err, i;
+
+	if (damon_sysfs_kdamonds_busy(kdamonds->kdamonds_arr, kdamonds->nr))
+		return -EBUSY;
+
+	damon_sysfs_kdamonds_rm_dirs(kdamonds);
+	if (!nr_kdamonds)
+		return 0;
+
+	kdamonds_arr = kmalloc_array(nr_kdamonds, sizeof(*kdamonds_arr),
+			GFP_KERNEL | __GFP_NOWARN);
+	if (!kdamonds_arr)
+		return -ENOMEM;
+	kdamonds->kdamonds_arr = kdamonds_arr;
+
+	for (i = 0; i < nr_kdamonds; i++) {
+		kdamond = damon_sysfs_kdamond_alloc();
+		if (!kdamond) {
+			damon_sysfs_kdamonds_rm_dirs(kdamonds);
+			return -ENOMEM;
+		}
+
+		err = kobject_init_and_add(&kdamond->kobj,
+				&damon_sysfs_kdamond_ktype, &kdamonds->kobj,
+				"%d", i);
+		if (err)
+			goto out;
+
+		err = damon_sysfs_kdamond_add_dirs(kdamond);
+		if (err)
+			goto out;
+
+		kdamonds_arr[i] = kdamond;
+		kdamonds->nr++;
+	}
+	return 0;
+
+out:
+	damon_sysfs_kdamonds_rm_dirs(kdamonds);
+	kobject_put(&kdamond->kobj);
+	return err;
+}
+
+static ssize_t nr_kdamonds_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	struct damon_sysfs_kdamonds *kdamonds = container_of(kobj,
+			struct damon_sysfs_kdamonds, kobj);
+
+	return sysfs_emit(buf, "%d\n", kdamonds->nr);
+}
+
+static ssize_t nr_kdamonds_store(struct kobject *kobj,
+		struct kobj_attribute *attr, const char *buf, size_t count)
+{
+	struct damon_sysfs_kdamonds *kdamonds;
+	int nr, err;
+
+	err = kstrtoint(buf, 0, &nr);
+	if (err)
+		return err;
+	if (nr < 0)
+		return -EINVAL;
+
+	kdamonds = container_of(kobj, struct damon_sysfs_kdamonds, kobj);
+
+	if (!mutex_trylock(&damon_sysfs_lock))
+		return -EBUSY;
+	err = damon_sysfs_kdamonds_add_dirs(kdamonds, nr);
+	mutex_unlock(&damon_sysfs_lock);
+	if (err)
+		return err;
+
+	return count;
+}
+
+static void damon_sysfs_kdamonds_release(struct kobject *kobj)
+{
+	kfree(container_of(kobj, struct damon_sysfs_kdamonds, kobj));
+}
+
+static struct kobj_attribute damon_sysfs_kdamonds_nr_attr =
+		__ATTR_RW_MODE(nr_kdamonds, 0600);
+
+static struct attribute *damon_sysfs_kdamonds_attrs[] = {
+	&damon_sysfs_kdamonds_nr_attr.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(damon_sysfs_kdamonds);
+
+static const struct kobj_type damon_sysfs_kdamonds_ktype = {
+	.release = damon_sysfs_kdamonds_release,
+	.sysfs_ops = &kobj_sysfs_ops,
+	.default_groups = damon_sysfs_kdamonds_groups,
+};
+
+/*
+ * damon user interface directory
+ */
+
+struct damon_sysfs_ui_dir {
+	struct kobject kobj;
+	struct damon_sysfs_kdamonds *kdamonds;
+};
+
+static struct damon_sysfs_ui_dir *damon_sysfs_ui_dir_alloc(void)
+{
+	return kzalloc(sizeof(struct damon_sysfs_ui_dir), GFP_KERNEL);
+}
+
+static int damon_sysfs_ui_dir_add_dirs(struct damon_sysfs_ui_dir *ui_dir)
+{
+	struct damon_sysfs_kdamonds *kdamonds;
+	int err;
+
+	kdamonds = damon_sysfs_kdamonds_alloc();
+	if (!kdamonds)
+		return -ENOMEM;
+
+	err = kobject_init_and_add(&kdamonds->kobj,
+			&damon_sysfs_kdamonds_ktype, &ui_dir->kobj,
+			"kdamonds");
+	if (err) {
+		kobject_put(&kdamonds->kobj);
+		return err;
+	}
+	ui_dir->kdamonds = kdamonds;
+	return err;
+}
+
+static void damon_sysfs_ui_dir_release(struct kobject *kobj)
+{
+	kfree(container_of(kobj, struct damon_sysfs_ui_dir, kobj));
+}
+
+static struct attribute *damon_sysfs_ui_dir_attrs[] = {
+	NULL,
+};
+ATTRIBUTE_GROUPS(damon_sysfs_ui_dir);
+
+static const struct kobj_type damon_sysfs_ui_dir_ktype = {
+	.release = damon_sysfs_ui_dir_release,
+	.sysfs_ops = &kobj_sysfs_ops,
+	.default_groups = damon_sysfs_ui_dir_groups,
+};
+
+static int __init damon_sysfs_init(void)
+{
+	struct kobject *damon_sysfs_root;
+	struct damon_sysfs_ui_dir *admin;
+	int err;
+
+	damon_sysfs_root = kobject_create_and_add("damon", mm_kobj);
+	if (!damon_sysfs_root)
+		return -ENOMEM;
+
+	admin = damon_sysfs_ui_dir_alloc();
+	if (!admin) {
+		kobject_put(damon_sysfs_root);
+		return -ENOMEM;
+	}
+	err = kobject_init_and_add(&admin->kobj, &damon_sysfs_ui_dir_ktype,
+			damon_sysfs_root, "admin");
+	if (err)
+		goto out;
+	err = damon_sysfs_ui_dir_add_dirs(admin);
+	if (err)
+		goto out;
+	return 0;
+
+out:
+	kobject_put(&admin->kobj);
+	kobject_put(damon_sysfs_root);
+	return err;
+}
+subsys_initcall(damon_sysfs_init);