mm/page_idle: constify 'struct bin_attribute'

The sysfs core now allows instances of 'struct bin_attribute' to be moved
into read-only memory.  Make use of that to protect them against
accidental or malicious modifications.

Link: https://lkml.kernel.org/r/20241216-sysfs-const-bin_attr-page_idle-v1-1-cc01ecc55196@weissschuh.net
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/page_idle.c

@@ -112,7 +112,7 @@ static void page_idle_clear_pte_refs(struct folio *folio)
 }
 
 static ssize_t page_idle_bitmap_read(struct file *file, struct kobject *kobj,
-				     struct bin_attribute *attr, char *buf,
+				     const struct bin_attribute *attr, char *buf,
 				     loff_t pos, size_t count)
 {
 	u64 *out = (u64 *)buf;
@@ -157,7 +157,7 @@ static ssize_t page_idle_bitmap_read(struct file *file, struct kobject *kobj,
 }
 
 static ssize_t page_idle_bitmap_write(struct file *file, struct kobject *kobj,
-				      struct bin_attribute *attr, char *buf,
+				      const struct bin_attribute *attr, char *buf,
 				      loff_t pos, size_t count)
 {
 	const u64 *in = (u64 *)buf;
@@ -193,17 +193,17 @@ static ssize_t page_idle_bitmap_write(struct file *file, struct kobject *kobj,
 	return (char *)in - buf;
 }
 
-static struct bin_attribute page_idle_bitmap_attr =
+static const struct bin_attribute page_idle_bitmap_attr =
 		__BIN_ATTR(bitmap, 0600,
 			   page_idle_bitmap_read, page_idle_bitmap_write, 0);
 
-static struct bin_attribute *page_idle_bin_attrs[] = {
+static const struct bin_attribute *const page_idle_bin_attrs[] = {
 	&page_idle_bitmap_attr,
 	NULL,
 };
 
 static const struct attribute_group page_idle_attr_group = {
-	.bin_attrs = page_idle_bin_attrs,
+	.bin_attrs_new = page_idle_bin_attrs,
 	.name = "page_idle",
 };