x86/resctrl: Constify kernfs_ops

The only usage of the kf_ops field in the rftype struct is to pass
it as argument to __kernfs_create_file(), which accepts a pointer to
const. Make it a pointer to const. This makes it possible to make
rdtgroup_kf_single_ops and kf_mondata_ops const, which allows the
compiler to put them in read-only memory.

Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://lkml.kernel.org/r/20201110230228.801785-1-rikard.falkeborn@gmail.com

arch/x86/kernel/cpu/resctrl/internal.h

@@ -264,7 +264,7 @@ void __exit rdtgroup_exit(void);
 struct rftype {
 	char			*name;
 	umode_t			mode;
-	struct kernfs_ops	*kf_ops;
+	const struct kernfs_ops	*kf_ops;
 	unsigned long		flags;
 	unsigned long		fflags;
 

arch/x86/kernel/cpu/resctrl/rdtgroup.c

@@ -240,13 +240,13 @@ static ssize_t rdtgroup_file_write(struct kernfs_open_file *of, char *buf,
 	return -EINVAL;
 }
 
-static struct kernfs_ops rdtgroup_kf_single_ops = {
+static const struct kernfs_ops rdtgroup_kf_single_ops = {
 	.atomic_write_len	= PAGE_SIZE,
 	.write			= rdtgroup_file_write,
 	.seq_show		= rdtgroup_seqfile_show,
 };
 
-static struct kernfs_ops kf_mondata_ops = {
+static const struct kernfs_ops kf_mondata_ops = {
 	.atomic_write_len	= PAGE_SIZE,
 	.seq_show		= rdtgroup_mondata_show,
 };