[PATCHv2 RFC net-next 01/14] rculist_bl: add hlist_bl_for_each_entry_continue_rcu

[Julian Anastasov <ja@xxxxxx>]

Change the old hlist_bl_first_rcu to hlist_bl_first_rcu_dereference
to indicate that it is a RCU dereference.

Add hlist_bl_next_rcu and hlist_bl_first_rcu to use RCU pointers
and use them to fix sparse warnings.

Add hlist_bl_for_each_entry_continue_rcu.

Signed-off-by: Julian Anastasov <ja@xxxxxx>
---
 include/linux/rculist_bl.h | 49 +++++++++++++++++++++++++++++++-------
 1 file changed, 40 insertions(+), 9 deletions(-)

diff --git a/include/linux/rculist_bl.h b/include/linux/rculist_bl.h
index 0b952d06eb0b..36363b876e53 100644
--- a/include/linux/rculist_bl.h
+++ b/include/linux/rculist_bl.h
@@ -8,21 +8,31 @@
 #include <linux/list_bl.h>
 #include <linux/rcupdate.h>
 
+/* return the first ptr or next element in an RCU protected list */
+#define hlist_bl_first_rcu(head)       \
+       (*((struct hlist_bl_node __rcu **)(&(head)->first)))
+#define hlist_bl_next_rcu(node)        \
+       (*((struct hlist_bl_node __rcu **)(&(node)->next)))
+
 static inline void hlist_bl_set_first_rcu(struct hlist_bl_head *h,
                                        struct hlist_bl_node *n)
 {
        LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
        LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) !=
                                                        LIST_BL_LOCKMASK);
-       rcu_assign_pointer(h->first,
+       rcu_assign_pointer(hlist_bl_first_rcu(h),
                (struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK));
 }
 
-static inline struct hlist_bl_node *hlist_bl_first_rcu(struct hlist_bl_head *h)
-{
-       return (struct hlist_bl_node *)
-               ((unsigned long)rcu_dereference_check(h->first, 
hlist_bl_is_locked(h)) & ~LIST_BL_LOCKMASK);
-}
+#define hlist_bl_first_rcu_dereference(head)                           \
+({                                                                     \
+       struct hlist_bl_head *__head = (head);                          \
+                                                                       \
+       (struct hlist_bl_node *)                                        \
+       ((unsigned long)rcu_dereference_check(hlist_bl_first_rcu(__head), \
+                                             hlist_bl_is_locked(__head)) & \
+                                             ~LIST_BL_LOCKMASK);       \
+})
 
 /**
  * hlist_bl_del_rcu - deletes entry from hash list without re-initialization
@@ -73,7 +83,7 @@ static inline void hlist_bl_add_head_rcu(struct hlist_bl_node 
*n,
 {
        struct hlist_bl_node *first;
 
-       /* don't need hlist_bl_first_rcu because we're under lock */
+       /* don't need hlist_bl_first_rcu* because we're under lock */
        first = hlist_bl_first(h);
 
        n->next = first;
@@ -93,9 +103,30 @@ static inline void hlist_bl_add_head_rcu(struct 
hlist_bl_node *n,
  *
  */
 #define hlist_bl_for_each_entry_rcu(tpos, pos, head, member)           \
-       for (pos = hlist_bl_first_rcu(head);                            \
+       for (pos = hlist_bl_first_rcu_dereference(head);                \
                pos &&                                                  \
                ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1; }); \
-               pos = rcu_dereference_raw(pos->next))
+               pos = rcu_dereference_raw(hlist_bl_next_rcu(pos)))
+
+/**
+ * hlist_bl_for_each_entry_continue_rcu - continue iteration over list of given
+ *   type
+ * @tpos:      the type * to use as a loop cursor.
+ * @pos:       the &struct hlist_bl_node to use as a loop cursor.
+ * @member:    the name of the hlist_bl_node within the struct.
+ *
+ * Continue to iterate over list of given type, continuing after
+ * the current position which must have been in the list when the RCU read
+ * lock was taken.
+ * This would typically require either that you obtained the node from a
+ * previous walk of the list in the same RCU read-side critical section, or
+ * that you held some sort of non-RCU reference (such as a reference count)
+ * to keep the node alive *and* in the list.
+ */
+#define hlist_bl_for_each_entry_continue_rcu(tpos, pos, member)                
\
+       for (pos = rcu_dereference_raw(hlist_bl_next_rcu(&(tpos)->member)); \
+            pos &&                                                     \
+            ({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1; }); \
+            pos = rcu_dereference_raw(hlist_bl_next_rcu(pos)))
 
 #endif
-- 
2.43.0