xfs: add a xattr_entry helper

Add a helper to translate from the item list head to the attr_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>

Author: Darrick J. Wong

fs/xfs/xfs_attr_item.c

@@ -391,6 +391,11 @@ xfs_attr_free_item(
 		kmem_cache_free(xfs_attr_intent_cache, attr);
 }
 
+static inline struct xfs_attr_intent *attri_entry(const struct list_head *e)
+{
+	return list_entry(e, struct xfs_attr_intent, xattri_list);
+}
+
 /* Process an attr. */
 STATIC int
 xfs_attr_finish_item(
@@ -399,11 +404,10 @@ xfs_attr_finish_item(
 	struct list_head		*item,
 	struct xfs_btree_cur		**state)
 {
-	struct xfs_attr_intent		*attr;
+	struct xfs_attr_intent		*attr = attri_entry(item);
 	struct xfs_da_args		*args;
 	int				error;
 
-	attr = container_of(item, struct xfs_attr_intent, xattri_list);
 	args = attr->xattri_da_args;
 
 	/* Reset trans after EAGAIN cycle since the transaction is new */
@@ -443,9 +447,8 @@ STATIC void
 xfs_attr_cancel_item(
 	struct list_head		*item)
 {
-	struct xfs_attr_intent		*attr;
+	struct xfs_attr_intent		*attr = attri_entry(item);
 
-	attr = container_of(item, struct xfs_attr_intent, xattri_list);
 	xfs_attr_free_item(attr);
 }