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 <a.hajda@samsung.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Mike Turquette <mturquette@linaro.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Greg KH <greg@kroah.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/kernfs/dir.c

@@ -412,7 +412,7 @@ void kernfs_put(struct kernfs_node *kn)
 	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,
@@ -506,12 +506,12 @@ static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
 					     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;
 	}
@@ -538,7 +538,7 @@ static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
  err_out2:
 	kmem_cache_free(kernfs_node_cache, kn);
  err_out1:
-	kfree(dup_name);
+	kfree_const(dup_name);
 	return NULL;
 }
 
@@ -1264,7 +1264,7 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
 	/* 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 {
@@ -1297,7 +1297,7 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
 	kernfs_link_sibling(kn);
 
 	kernfs_put(old_parent);
-	kfree(old_name);
+	kfree_const(old_name);
 
 	error = 0;
  out: