[PATCH 3/5] list.h: synchronize hlist_for_each_entry* iterators with linux

[Rasmus Villemoes]

All the way back in 2013, the linux kernel updated the four
hlist_for_each_entry* iterators to require one less auxiliary
variable:

  commit b67bfe0d42cac56c512dd5da4b1b347a23f4b70a
  Author: Sasha Levin <sasha.levin at oracle.com>
  Date:   Wed Feb 27 17:06:00 2013 -0800

      hlist: drop the node parameter from iterators

Currently, there is only one "user" of any of these, namely in
fs/ubifs/super.c, but that actually uses the "new-style" form, and
is (obviously, or it wouldn't have built) inside #ifndef __UBOOT__.

Before adding actual users of these, import the version as of linux
v6.1-rc1, including the hlist_entry_safe() helper used by the new
versions.

Signed-off-by: Rasmus Villemoes <rasmus.villemoes at prevas.dk>
---
 include/linux/list.h | 53 +++++++++++++++++++++-----------------------
 1 file changed, 25 insertions(+), 28 deletions(-)

diff --git a/include/linux/list.h b/include/linux/list.h
index 3eacf68e3a..6910721c00 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -646,54 +646,51 @@ static inline void hlist_add_after(struct hlist_node *n,
 	for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
 	     pos = n)
 
+#define hlist_entry_safe(ptr, type, member) \
+	({ typeof(ptr) ____ptr = (ptr); \
+	   ____ptr ? hlist_entry(____ptr, type, member) : NULL; \
+	})
+
 /**
  * hlist_for_each_entry	- iterate over list of given type
- * @tpos:	the type * to use as a loop cursor.
- * @pos:	the &struct hlist_node to use as a loop cursor.
+ * @pos:	the type * to use as a loop cursor.
  * @head:	the head for your list.
  * @member:	the name of the hlist_node within the struct.
  */
-#define hlist_for_each_entry(tpos, pos, head, member)			 \
-	for (pos = (head)->first;					 \
-	     pos && ({ prefetch(pos->next); 1;}) &&			 \
-		({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
-	     pos = pos->next)
+#define hlist_for_each_entry(pos, head, member)				\
+	for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\
+	     pos;							\
+	     pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
 
 /**
  * hlist_for_each_entry_continue - iterate over a hlist continuing after current point
- * @tpos:	the type * to use as a loop cursor.
- * @pos:	the &struct hlist_node to use as a loop cursor.
+ * @pos:	the type * to use as a loop cursor.
  * @member:	the name of the hlist_node within the struct.
  */
-#define hlist_for_each_entry_continue(tpos, pos, member)		 \
-	for (pos = (pos)->next;						 \
-	     pos && ({ prefetch(pos->next); 1;}) &&			 \
-		({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
-	     pos = pos->next)
+#define hlist_for_each_entry_continue(pos, member)			\
+	for (pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member);\
+	     pos;							\
+	     pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
 
 /**
  * hlist_for_each_entry_from - iterate over a hlist continuing from current point
- * @tpos:	the type * to use as a loop cursor.
- * @pos:	the &struct hlist_node to use as a loop cursor.
+ * @pos:	the type * to use as a loop cursor.
  * @member:	the name of the hlist_node within the struct.
  */
-#define hlist_for_each_entry_from(tpos, pos, member)			 \
-	for (; pos && ({ prefetch(pos->next); 1;}) &&			 \
-		({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
-	     pos = pos->next)
+#define hlist_for_each_entry_from(pos, member)				\
+	for (; pos;							\
+	     pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
 
 /**
  * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
- * @tpos:	the type * to use as a loop cursor.
- * @pos:	the &struct hlist_node to use as a loop cursor.
- * @n:		another &struct hlist_node to use as temporary storage
+ * @pos:	the type * to use as a loop cursor.
+ * @n:		a &struct hlist_node to use as temporary storage
  * @head:	the head for your list.
  * @member:	the name of the hlist_node within the struct.
  */
-#define hlist_for_each_entry_safe(tpos, pos, n, head, member)		 \
-	for (pos = (head)->first;					 \
-	     pos && ({ n = pos->next; 1; }) &&				 \
-		({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
-	     pos = n)
+#define hlist_for_each_entry_safe(pos, n, head, member) 		\
+	for (pos = hlist_entry_safe((head)->first, typeof(*pos), member);\
+	     pos && ({ n = pos->member.next; 1; });			\
+	     pos = hlist_entry_safe(n, typeof(*pos), member))
 
 #endif
-- 
2.37.2