[PATCH 6/8] mm/damon/sysfs-schemes: return error when for attempts to install filters on wrong sysfs directory

[SeongJae Park <sj@kernel.org>]

Return error if the user tries to install a DAMOS filter on DAMOS
filters sysfs directory that assumed to be used for filters that handled
by a DAMON layer that not same to that for the installing filter.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/sysfs-schemes.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index b9f035f4b00f..ed834622df2a 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -362,6 +362,23 @@ static ssize_t type_show(struct kobject *kobj,
 			damon_sysfs_scheme_filter_type_strs[filter->type]);
 }
 
+static bool damos_sysfs_scheme_filter_valid_type(
+		enum damos_sysfs_filter_handle_layer layer,
+		enum damos_filter_type type)
+{
+	switch (layer) {
+	case DAMOS_SYSFS_FILTER_HANDLE_LAYER_BOTH:
+		return true;
+	case DAMOS_SYSFS_FILTER_HANDLE_LAYER_CORE:
+		return !damos_filter_for_ops(type);
+	case DAMOS_SYSFS_FILTER_HANDLE_LAYER_OPS:
+		return damos_filter_for_ops(type);
+	default:
+		break;
+	}
+	return false;
+}
+
 static ssize_t type_store(struct kobject *kobj,
 		struct kobj_attribute *attr, const char *buf, size_t count)
 {
@@ -373,6 +390,9 @@ static ssize_t type_store(struct kobject *kobj,
 	for (type = 0; type < NR_DAMOS_FILTER_TYPES; type++) {
 		if (sysfs_streq(buf, damon_sysfs_scheme_filter_type_strs[
 					type])) {
+			if (!damos_sysfs_scheme_filter_valid_type(
+						filter->handle_layer, type))
+				break;
 			filter->type = type;
 			ret = count;
 			break;
-- 
2.39.5