[RFC PATCH v2.2 10/17] mm/damon/sysfs: implement preps/nr_preps file

[SJ Park <sj@kernel.org>]

Implement nr_preps file under the preps directory.  It will be evolved
to be used for generating sub directories that will represent each probe
preparation action.

Signed-off-by: SJ Park <sj@kernel.org>
---
 mm/damon/sysfs.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 52 insertions(+), 1 deletion(-)

diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c
index 66a3e7de869a8..38affef08d0fb 100644
--- a/mm/damon/sysfs.c
+++ b/mm/damon/sysfs.c
@@ -756,6 +756,7 @@ static const struct kobj_type damon_sysfs_intervals_ktype = {
 
 struct damon_sysfs_preps {
 	struct kobject kobj;
+	int nr;
 };
 
 static struct damon_sysfs_preps *damon_sysfs_preps_alloc(void)
@@ -763,12 +764,60 @@ static struct damon_sysfs_preps *damon_sysfs_preps_alloc(void)
 	return kzalloc_obj(struct damon_sysfs_preps);
 }
 
+static void damon_sysfs_preps_rm_dirs(struct damon_sysfs_preps *preps)
+{
+	preps->nr = 0;
+}
+
+static int damon_sysfs_preps_add_dirs(struct damon_sysfs_preps *preps,
+		int nr_preps)
+{
+	preps->nr = nr_preps;
+	return 0;
+}
+
+static ssize_t nr_preps_show(struct kobject *kobj, struct kobj_attribute *attr,
+		char *buf)
+{
+	struct damon_sysfs_preps *preps = container_of(kobj,
+			struct damon_sysfs_preps, kobj);
+
+	return sysfs_emit(buf, "%d\n", preps->nr);
+}
+
+static ssize_t nr_preps_store(struct kobject *kobj,
+		struct kobj_attribute *attr, const char *buf, size_t count)
+{
+	struct damon_sysfs_preps *preps;
+	int nr, err = kstrtoint(buf, 0, &nr);
+
+	if (err)
+		return err;
+	if (nr < 0)
+		return -EINVAL;
+
+	preps = container_of(kobj, struct damon_sysfs_preps, kobj);
+
+	if (!mutex_trylock(&damon_sysfs_lock))
+		return -EBUSY;
+	err = damon_sysfs_preps_add_dirs(preps, nr);
+	mutex_unlock(&damon_sysfs_lock);
+	if (err)
+		return err;
+
+	return count;
+}
+
 static void damon_sysfs_preps_release(struct kobject *kobj)
 {
 	kfree(container_of(kobj, struct damon_sysfs_preps, kobj));
 }
 
+static struct kobj_attribute damon_sysfs_preps_nr_attr =
+		__ATTR_RW_MODE(nr_preps, 0600);
+
 static struct attribute *damon_sysfs_preps_attrs[] = {
+	&damon_sysfs_preps_nr_attr.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(damon_sysfs_preps);
@@ -1150,8 +1199,10 @@ static int damon_sysfs_probe_add_dirs(struct damon_sysfs_probe *probe)
 
 static void damon_sysfs_probe_rm_dirs(struct damon_sysfs_probe *probe)
 {
-	if (probe->preps)
+	if (probe->preps) {
+		damon_sysfs_preps_rm_dirs(probe->preps);
 		kobject_put(&probe->preps->kobj);
+	}
 	if (probe->filters) {
 		damon_sysfs_filters_rm_dirs(probe->filters);
 		kobject_put(&probe->filters->kobj);
-- 
2.47.3