kernfs: convert node name allocation to kstrdup_const

sysfs frequently performs duplication of strings located in read-only
memory section. Replacing kstrdup by kstrdup_const allows to avoid such
operations.

Signed-off-by: Andrzej Hajda <[e-mail]>
Cc: Marek Szyprowski <[e-mail]>
Cc: Kyungmin Park <[e-mail]>
Cc: Mike Turquette <[e-mail]>
Cc: Alexander Viro <[e-mail]>
Cc: Christoph Lameter <[e-mail]>
Cc: Pekka Enberg <[e-mail]>
Cc: David Rientjes <[e-mail]>
Cc: Joonsoo Kim <[e-mail]>
Acked-by: Tejun Heo <[e-mail]>
Cc: Greg KH <[e-mail]>
Cc: Geert Uytterhoeven <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

fs/kernfs/dir.c

···
 	if (kernfs_type(kn) == KERNFS_LINK)
 		kernfs_put(kn->symlink.target_kn);
 	if (!(kn->flags & KERNFS_STATIC_NAME))
-		kfree(kn->name);
+		kfree_const(kn->name);
 	if (kn->iattr) {
 		if (kn->iattr->ia_secdata)
 			security_release_secctx(kn->iattr->ia_secdata,
···
 					     const char *name, umode_t mode,
 					     unsigned flags)
 {
-	char *dup_name = NULL;
+	const char *dup_name = NULL;
 	struct kernfs_node *kn;
 	int ret;
 
 	if (!(flags & KERNFS_STATIC_NAME)) {
-		name = dup_name = kstrdup(name, GFP_KERNEL);
+		name = dup_name = kstrdup_const(name, GFP_KERNEL);
 		if (!name)
 			return NULL;
 	}
···
  err_out2:
 	kmem_cache_free(kernfs_node_cache, kn);
  err_out1:
-	kfree(dup_name);
+	kfree_const(dup_name);
 	return NULL;
 }
 
···
 	/* rename kernfs_node */
 	if (strcmp(kn->name, new_name) != 0) {
 		error = -ENOMEM;
-		new_name = kstrdup(new_name, GFP_KERNEL);
+		new_name = kstrdup_const(new_name, GFP_KERNEL);
 		if (!new_name)
 			goto out;
 	} else {
···
 	kernfs_link_sibling(kn);
 
 	kernfs_put(old_parent);
-	kfree(old_name);
+	kfree_const(old_name);
 
 	error = 0;
  out: