devres: move the size check from alloc_dr() into a separate function

We will perform the same size check in devm_krealloc(). Move the relevant
code into a separate helper.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Link: https://lore.kernel.org/r/20200629065008.27620-3-brgl@bgdev.plSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/devres.c

@@ -89,15 +89,23 @@ static struct devres_group * node_to_group(struct devres_node *node)
 	return NULL;
 }
 
+static bool check_dr_size(size_t size, size_t *tot_size)
+{
+	/* We must catch any near-SIZE_MAX cases that could overflow. */
+	if (unlikely(check_add_overflow(sizeof(struct devres),
+					size, tot_size)))
+		return false;
+
+	return true;
+}
+
 static __always_inline struct devres * alloc_dr(dr_release_t release,
 						size_t size, gfp_t gfp, int nid)
 {
 	size_t tot_size;
 	struct devres *dr;
 
-	/* We must catch any near-SIZE_MAX cases that could overflow. */
-	if (unlikely(check_add_overflow(sizeof(struct devres), size,
-					&tot_size)))
+	if (!check_dr_size(size, &tot_size))
 		return NULL;
 
 	dr = kmalloc_node_track_caller(tot_size, gfp, nid);