Implement a sysfs directory for letting the users to configure each data
probe filter.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/sysfs.c | 125 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 124 insertions(+), 1 deletion(-)

diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c
index 250208d3de21b..25487a0268cbe 100644
--- a/mm/damon/sysfs.c
+++ b/mm/damon/sysfs.c
@@ -747,12 +747,46 @@ static const struct kobj_type damon_sysfs_intervals_ktype = {
 	.default_groups = damon_sysfs_intervals_groups,
 };
 
+/*
+ * filter directory
+ */
+
+struct damon_sysfs_filter {
+	struct kobject kobj;
+};
+
+static struct damon_sysfs_filter *damon_sysfs_filter_alloc(void)
+{
+	return kzalloc_obj(struct damon_sysfs_filter);
+}
+
+static void damon_sysfs_filter_release(struct kobject *kobj)
+{
+	struct damon_sysfs_filter *filter = container_of(kobj,
+			struct damon_sysfs_filter, kobj);
+
+	kfree(filter);
+}
+
+static struct attribute *damon_sysfs_filter_attrs[] = {
+	NULL,
+};
+ATTRIBUTE_GROUPS(damon_sysfs_filter);
+
+static const struct kobj_type damon_sysfs_filter_ktype = {
+	.release = damon_sysfs_filter_release,
+	.sysfs_ops = &kobj_sysfs_ops,
+	.default_groups = damon_sysfs_filter_groups,
+};
+
 /*
  * filters directory
  */
 
 struct damon_sysfs_filters {
 	struct kobject kobj;
+	struct damon_sysfs_filter **filters_arr;
+	int nr;
 };
 
 static struct damon_sysfs_filters *damon_sysfs_filters_alloc(void)
@@ -760,12 +794,98 @@ static struct damon_sysfs_filters *damon_sysfs_filters_alloc(void)
 	return kzalloc_obj(struct damon_sysfs_filters);
 }
 
+static void damon_sysfs_filters_rm_dirs(struct damon_sysfs_filters *filters)
+{
+	struct damon_sysfs_filter **filters_arr = filters->filters_arr;
+	int i;
+
+	for (i = 0; i < filters->nr; i++)
+		kobject_put(&filters_arr[i]->kobj);
+	filters->nr = 0;
+	kfree(filters_arr);
+	filters->filters_arr = NULL;
+}
+
+static int damon_sysfs_filters_add_dirs(
+		struct damon_sysfs_filters *filters, int nr_filters)
+{
+	struct damon_sysfs_filter **filters_arr, *filter;
+	int err, i;
+
+	damon_sysfs_filters_rm_dirs(filters);
+	if (!nr_filters)
+		return 0;
+
+	filters_arr = kmalloc_objs(*filters_arr, nr_filters,
+				   GFP_KERNEL | __GFP_NOWARN);
+	if (!filters_arr)
+		return -ENOMEM;
+	filters->filters_arr = filters_arr;
+
+	for (i = 0; i < nr_filters; i++) {
+		filter = damon_sysfs_filter_alloc();
+		if (!filter) {
+			damon_sysfs_filters_rm_dirs(filters);
+			return -ENOMEM;
+		}
+
+		err = kobject_init_and_add(&filter->kobj,
+				&damon_sysfs_filter_ktype, &filters->kobj,
+				"%d", i);
+		if (err) {
+			kobject_put(&filter->kobj);
+			damon_sysfs_filters_rm_dirs(filters);
+			return err;
+		}
+
+		filters_arr[i] = filter;
+		filters->nr++;
+	}
+	return 0;
+}
+
+static ssize_t nr_filters_show(struct kobject *kobj,
+		struct kobj_attribute *attr, char *buf)
+{
+	struct damon_sysfs_filters *filters = container_of(kobj,
+			struct damon_sysfs_filters, kobj);
+
+	return sysfs_emit(buf, "%d\n", filters->nr);
+}
+
+static ssize_t nr_filters_store(struct kobject *kobj,
+		struct kobj_attribute *attr, const char *buf, size_t count)
+{
+	struct damon_sysfs_filters *filters;
+	int nr, err = kstrtoint(buf, 0, &nr);
+
+	if (err)
+		return err;
+	if (nr < 0)
+		return -EINVAL;
+
+	filters = container_of(kobj, struct damon_sysfs_filters, kobj);
+
+	if (!mutex_trylock(&damon_sysfs_lock))
+		return -EBUSY;
+	err = damon_sysfs_filters_add_dirs(filters, nr);
+	mutex_unlock(&damon_sysfs_lock);
+	if (err)
+		return err;
+
+	return count;
+}
+
 static void damon_sysfs_filters_release(struct kobject *kobj)
 {
 	kfree(container_of(kobj, struct damon_sysfs_filters, kobj));
 }
 
+static struct kobj_attribute damon_sysfs_filters_nr_attr =
+		__ATTR_RW_MODE(nr_filters, 0600);
+
 static struct attribute *damon_sysfs_filters_attrs[] = {
+	&damon_sysfs_filters_nr_attr.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(damon_sysfs_filters);
@@ -811,7 +931,10 @@ static int damon_sysfs_probe_add_dirs(struct damon_sysfs_probe *attr)
 
 static void damon_sysfs_probe_rm_dirs(struct damon_sysfs_probe *attr)
 {
-	kobject_put(&attr->filters->kobj);
+	if (attr->filters) {
+		damon_sysfs_filters_rm_dirs(attr->filters);
+		kobject_put(&attr->filters->kobj);
+	}
 }
 
 static void damon_sysfs_probe_release(struct kobject *kobj)
-- 
2.47.3