xfs: add a bi_entry helper

Add a helper to translate from the item list head to the bmap_intent
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_bmap_item.c

@@ -221,18 +221,21 @@ static const struct xfs_item_ops xfs_bud_item_ops = {
 	.iop_intent	= xfs_bud_item_intent,
 };
 
+static inline struct xfs_bmap_intent *bi_entry(const struct list_head *e)
+{
+	return list_entry(e, struct xfs_bmap_intent, bi_list);
+}
+
 /* Sort bmap intents by inode. */
 static int
 xfs_bmap_update_diff_items(
 	void				*priv,
 	const struct list_head		*a,
 	const struct list_head		*b)
 {
-	struct xfs_bmap_intent		*ba;
-	struct xfs_bmap_intent		*bb;
+	struct xfs_bmap_intent		*ba = bi_entry(a);
+	struct xfs_bmap_intent		*bb = bi_entry(b);
 
-	ba = container_of(a, struct xfs_bmap_intent, bi_list);
-	bb = container_of(b, struct xfs_bmap_intent, bi_list);
 	return ba->bi_owner->i_ino - bb->bi_owner->i_ino;
 }
 
@@ -348,11 +351,9 @@ xfs_bmap_update_finish_item(
 	struct list_head		*item,
 	struct xfs_btree_cur		**state)
 {
-	struct xfs_bmap_intent		*bi;
+	struct xfs_bmap_intent		*bi = bi_entry(item);
 	int				error;
 
-	bi = container_of(item, struct xfs_bmap_intent, bi_list);
-
 	error = xfs_bmap_finish_one(tp, bi);
 	if (!error && bi->bi_bmap.br_blockcount > 0) {
 		ASSERT(bi->bi_type == XFS_BMAP_UNMAP);
@@ -377,9 +378,7 @@ STATIC void
 xfs_bmap_update_cancel_item(
 	struct list_head		*item)
 {
-	struct xfs_bmap_intent		*bi;
-
-	bi = container_of(item, struct xfs_bmap_intent, bi_list);
+	struct xfs_bmap_intent		*bi = bi_entry(item);
 
 	xfs_bmap_update_put_group(bi);
 	kmem_cache_free(xfs_bmap_intent_cache, bi);