mm/damon/sysfs-schemes: record filters of which layer should be added to the given filters directory

Unlike their name and assumed purposes, {core,ops}_filters DAMOS sysfs
directories are allowing installing any type of filters.  As a first step
for preventing such wrong installments, add information about filters that
handled by what layer should the installed to the given filters directory
in the DAMOS sysfs internal data structures.

Link: https://lkml.kernel.org/r/20250305222733.59089-6-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: sjp38

mm/damon/sysfs-schemes.c

@@ -309,8 +309,18 @@ static const struct kobj_type damon_sysfs_stats_ktype = {
  * filter directory
  */
 
+/*
+ * enum damos_sysfs_filter_handle_layer - Layers handling filters of a dir.
+ */
+enum damos_sysfs_filter_handle_layer {
+	DAMOS_SYSFS_FILTER_HANDLE_LAYER_CORE,
+	DAMOS_SYSFS_FILTER_HANDLE_LAYER_OPS,
+	DAMOS_SYSFS_FILTER_HANDLE_LAYER_BOTH,
+};
+
 struct damon_sysfs_scheme_filter {
 	struct kobject kobj;
+	enum damos_sysfs_filter_handle_layer handle_layer;
 	enum damos_filter_type type;
 	bool matching;
 	bool allow;
@@ -320,9 +330,15 @@ struct damon_sysfs_scheme_filter {
 	int target_idx;
 };
 
-static struct damon_sysfs_scheme_filter *damon_sysfs_scheme_filter_alloc(void)
+static struct damon_sysfs_scheme_filter *damon_sysfs_scheme_filter_alloc(
+		enum damos_sysfs_filter_handle_layer layer)
 {
-	return kzalloc(sizeof(struct damon_sysfs_scheme_filter), GFP_KERNEL);
+	struct damon_sysfs_scheme_filter *filter;
+
+	filter = kzalloc(sizeof(struct damon_sysfs_scheme_filter), GFP_KERNEL);
+	if (filter)
+		filter->handle_layer = layer;
+	return filter;
 }
 
 /* Should match with enum damos_filter_type */
@@ -595,14 +611,20 @@ static const struct kobj_type damon_sysfs_scheme_filter_ktype = {
 
 struct damon_sysfs_scheme_filters {
 	struct kobject kobj;
+	enum damos_sysfs_filter_handle_layer handle_layer;
 	struct damon_sysfs_scheme_filter **filters_arr;
 	int nr;
 };
 
 static struct damon_sysfs_scheme_filters *
-damon_sysfs_scheme_filters_alloc(void)
+damon_sysfs_scheme_filters_alloc(enum damos_sysfs_filter_handle_layer layer)
 {
-	return kzalloc(sizeof(struct damon_sysfs_scheme_filters), GFP_KERNEL);
+	struct damon_sysfs_scheme_filters *filters;
+
+	filters = kzalloc(sizeof(struct damon_sysfs_scheme_filters), GFP_KERNEL);
+	if (filters)
+		filters->handle_layer = layer;
+	return filters;
 }
 
 static void damon_sysfs_scheme_filters_rm_dirs(
@@ -635,7 +657,8 @@ static int damon_sysfs_scheme_filters_add_dirs(
 	filters->filters_arr = filters_arr;
 
 	for (i = 0; i < nr_filters; i++) {
-		filter = damon_sysfs_scheme_filter_alloc();
+		filter = damon_sysfs_scheme_filter_alloc(
+				filters->handle_layer);
 		if (!filter) {
 			damon_sysfs_scheme_filters_rm_dirs(filters);
 			return -ENOMEM;
@@ -1607,11 +1630,11 @@ static int damon_sysfs_scheme_set_watermarks(struct damon_sysfs_scheme *scheme)
 }
 
 static int damon_sysfs_scheme_set_filters(struct damon_sysfs_scheme *scheme,
-		const char *name,
+		enum damos_sysfs_filter_handle_layer layer, const char *name,
 		struct damon_sysfs_scheme_filters **filters_ptr)
 {
 	struct damon_sysfs_scheme_filters *filters =
-		damon_sysfs_scheme_filters_alloc();
+		damon_sysfs_scheme_filters_alloc(layer);
 	int err;
 
 	if (!filters)
@@ -1630,15 +1653,18 @@ static int damos_sysfs_set_filter_dirs(struct damon_sysfs_scheme *scheme)
 {
 	int err;
 
-	err = damon_sysfs_scheme_set_filters(scheme, "filters",
+	err = damon_sysfs_scheme_set_filters(scheme,
+			DAMOS_SYSFS_FILTER_HANDLE_LAYER_BOTH, "filters",
 			&scheme->filters);
 	if (err)
 		return err;
-	err = damon_sysfs_scheme_set_filters(scheme, "core_filters",
+	err = damon_sysfs_scheme_set_filters(scheme,
+			DAMOS_SYSFS_FILTER_HANDLE_LAYER_CORE, "core_filters",
 			&scheme->core_filters);
 	if (err)
 		goto put_filters_out;
-	err = damon_sysfs_scheme_set_filters(scheme, "ops_filters",
+	err = damon_sysfs_scheme_set_filters(scheme,
+			DAMOS_SYSFS_FILTER_HANDLE_LAYER_OPS, "ops_filters",
 			&scheme->ops_filters);
 	if (err)
 		goto put_core_filters_out;