xfs: add a ci_entry helper

Add a helper to translate from the item list head to the
refcount_intent_item structure and use it so shorten assignments and
avoid the need for extra local variables.
Inspired-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/xfs_refcount_item.c

@@ -227,6 +227,11 @@ static const struct xfs_item_ops xfs_cud_item_ops = {
 	.iop_intent	= xfs_cud_item_intent,
 };
 
+static inline struct xfs_refcount_intent *ci_entry(const struct list_head *e)
+{
+	return list_entry(e, struct xfs_refcount_intent, ri_list);
+}
+
 /* Sort refcount intents by AG. */
 static int
 xfs_refcount_update_diff_items(
@@ -234,11 +239,8 @@ xfs_refcount_update_diff_items(
 	const struct list_head		*a,
 	const struct list_head		*b)
 {
-	struct xfs_refcount_intent	*ra;
-	struct xfs_refcount_intent	*rb;
-
-	ra = container_of(a, struct xfs_refcount_intent, ri_list);
-	rb = container_of(b, struct xfs_refcount_intent, ri_list);
+	struct xfs_refcount_intent	*ra = ci_entry(a);
+	struct xfs_refcount_intent	*rb = ci_entry(b);
 
 	return ra->ri_pag->pag_agno - rb->ri_pag->pag_agno;
 }
@@ -341,11 +343,9 @@ xfs_refcount_update_finish_item(
 	struct list_head		*item,
 	struct xfs_btree_cur		**state)
 {
-	struct xfs_refcount_intent	*ri;
+	struct xfs_refcount_intent	*ri = ci_entry(item);
 	int				error;
 
-	ri = container_of(item, struct xfs_refcount_intent, ri_list);
-
 	/* Did we run out of reservation?  Requeue what we didn't finish. */
 	error = xfs_refcount_finish_one(tp, ri, state);
 	if (!error && ri->ri_blockcount > 0) {
@@ -372,9 +372,7 @@ STATIC void
 xfs_refcount_update_cancel_item(
 	struct list_head		*item)
 {
-	struct xfs_refcount_intent	*ri;
-
-	ri = container_of(item, struct xfs_refcount_intent, ri_list);
+	struct xfs_refcount_intent	*ri = ci_entry(item);
 
 	xfs_refcount_update_put_group(ri);
 	kmem_cache_free(xfs_refcount_intent_cache, ri);