Implement preps/nr file write operation to really create the probe prep
directories and their files.

Signed-off-by: SJ Park <sj@kernel.org>
---
 mm/damon/sysfs.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 53 insertions(+), 1 deletion(-)

diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c
index b15ec082109b7..f275a6f73eee1 100644
--- a/mm/damon/sysfs.c
+++ b/mm/damon/sysfs.c
@@ -759,6 +759,17 @@ struct damon_sysfs_prep {
 	enum damon_prep_action action;
 };
 
+static struct damon_sysfs_prep *damon_sysfs_prep_alloc(void)
+{
+	struct damon_sysfs_prep *prep;
+
+	prep = kzalloc_obj(struct damon_sysfs_prep);
+	if (!prep)
+		return prep;
+	prep->action = DAMON_PREP_SET_PGIDLE;
+	return prep;
+}
+
 struct damon_sysfs_prep_action_name {
 	enum damon_prep_action action;
 	char *name;
@@ -839,6 +850,7 @@ static const struct kobj_type damon_sysfs_prep_ktype = {
 
 struct damon_sysfs_preps {
 	struct kobject kobj;
+	struct damon_sysfs_prep **preps_arr;
 	int nr;
 };
 
@@ -849,13 +861,53 @@ static struct damon_sysfs_preps *damon_sysfs_preps_alloc(void)
 
 static void damon_sysfs_preps_rm_dirs(struct damon_sysfs_preps *preps)
 {
+	struct damon_sysfs_prep **preps_arr = preps->preps_arr;
+	int i;
+
+	for (i = 0; i < preps->nr; i++) {
+		kobject_del(&preps_arr[i]->kobj);
+		kobject_put(&preps_arr[i]->kobj);
+	}
 	preps->nr = 0;
+	kfree(preps_arr);
+	preps->preps_arr = NULL;
 }
 
 static int damon_sysfs_preps_add_dirs(struct damon_sysfs_preps *preps,
 		int nr_preps)
 {
-	preps->nr = nr_preps;
+	struct damon_sysfs_prep **preps_arr, *prep;
+	int err, i;
+
+	damon_sysfs_preps_rm_dirs(preps);
+	if (!nr_preps)
+		return 0;
+
+	preps_arr = kmalloc_objs(*preps_arr, nr_preps,
+				   GFP_KERNEL | __GFP_NOWARN);
+	if (!preps_arr)
+		return -ENOMEM;
+	preps->preps_arr = preps_arr;
+
+	for (i = 0; i < nr_preps; i++) {
+		prep = damon_sysfs_prep_alloc();
+		if (!prep) {
+			damon_sysfs_preps_rm_dirs(preps);
+			return -ENOMEM;
+		}
+
+		err = kobject_init_and_add(&prep->kobj,
+				&damon_sysfs_prep_ktype, &preps->kobj, "%d",
+				i);
+		if (err) {
+			kobject_put(&prep->kobj);
+			damon_sysfs_preps_rm_dirs(preps);
+			return err;
+		}
+
+		preps_arr[i] = prep;
+		preps->nr++;
+	}
 	return 0;
 }
 
-- 
2.47.3