[PATCH 0/4] list: introduce list_next/prev_entry

[PATCH 0/4] list: introduce list_next/prev_entry

[Oleg Nesterov]

Hello.

Not sure who maintains list.h, hopefully this is -mm material.

It is really annoying that we do not have list_next/prev_entry,
they can have a lot of users, including list.h itself.

And in fact list_next_entry() is already defined in events/core.c
and bnx2x_sp.c, this proves that it is really handy. That is why
1/4 comes as a separate patch because it touches the code outside
of list.h.

3/4 is minor, but I think makes sense anyway.

4/4 is just the random example of usage outside of list.h,
list_entry(child->d_u.d_child.next, struct dentry, d_u.d_child)
is hardly readable.

None of this patches changes the compiled code.

Oleg.

 drivers/net/ethernet/broadcom/bnx2x/bnx2x_sp.c |    3 -
 fs/debugfs/inode.c                             |    3 +-
 include/linux/list.h                           |   79 ++++++++++++++++--------
 kernel/events/core.c                           |    3 -
 4 files changed, 54 insertions(+), 34 deletions(-)

[PATCH 1/4] list: introduce list_next_entry() and list_prev_entry()

[Oleg Nesterov]

Add 2 trivial helpers list_next_entry() and list_prev_entry(),
they can have a lot of users including list.h itself. In fact
the 1st one is already defined in events/core.c and bnx2x_sp.c,
so the patch simply moves the definition to list.h.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 drivers/net/ethernet/broadcom/bnx2x/bnx2x_sp.c |    3 ---
 include/linux/list.h                           |   16 ++++++++++++++++
 kernel/events/core.c                           |    3 ---
 3 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_sp.c b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_sp.c
index 9fbeee5..32c92ab 100644
--- a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_sp.c
+++ b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_sp.c
@@ -1217,9 +1217,6 @@ static void bnx2x_set_one_vlan_mac_e1h(struct bnx2x *bp,
 				     ETH_VLAN_FILTER_CLASSIFY, config);
 }
 
-#define list_next_entry(pos, member) \
-	list_entry((pos)->member.next, typeof(*(pos)), member)
-
 /**
  * bnx2x_vlan_mac_restore - reconfigure next MAC/VLAN/VLAN-MAC element
  *
diff --git a/include/linux/list.h b/include/linux/list.h
index f4d8a2f..2ece638 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -373,6 +373,22 @@ static inline void list_splice_tail_init(struct list_head *list,
 	(!list_empty(ptr) ? list_first_entry(ptr, type, member) : NULL)
 
 /**
+ * list_next_entry - get the next element in list
+ * @pos:	the type * to cursor
+ * @member:	the name of the list_struct within the struct.
+ */
+#define list_next_entry(pos, member) \
+	list_entry((pos)->member.next, typeof(*(pos)), member)
+
+/**
+ * list_prev_entry - get the prev element in list
+ * @pos:	the type * to cursor
+ * @member:	the name of the list_struct within the struct.
+ */
+#define list_prev_entry(pos, member) \
+	list_entry((pos)->member.prev, typeof(*(pos)), member)
+
+/**
  * list_for_each	-	iterate over a list
  * @pos:	the &struct list_head to use as a loop cursor.
  * @head:	the head for your list.
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 953c143..8429d05 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -2210,9 +2210,6 @@ static void __perf_event_sync_stat(struct perf_event *event,
 	perf_event_update_userpage(next_event);
 }
 
-#define list_next_entry(pos, member) \
-	list_entry(pos->member.next, typeof(*pos), member)
-
 static void perf_event_sync_stat(struct perf_event_context *ctx,
 				   struct perf_event_context *next_ctx)
 {
-- 
1.5.5.1

[PATCH 2/4] list: change list_for_each_entry*() to use list_*_entry()

[Oleg Nesterov]

Now that we have list_{next,prev}_entry() we can change
list_for_each_entry*() and list_safe_reset_next() to use the
new helpers to improve the readability.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 include/linux/list.h |   44 ++++++++++++++++++++++----------------------
 1 files changed, 22 insertions(+), 22 deletions(-)

diff --git a/include/linux/list.h b/include/linux/list.h
index 2ece638..c88a591 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -433,8 +433,8 @@ static inline void list_splice_tail_init(struct list_head *list,
  */
 #define list_for_each_entry(pos, head, member)				\
 	for (pos = list_entry((head)->next, typeof(*pos), member);	\
-	     &pos->member != (head); 	\
-	     pos = list_entry(pos->member.next, typeof(*pos), member))
+	     &pos->member != (head);					\
+	     pos = list_next_entry(pos, member))
 
 /**
  * list_for_each_entry_reverse - iterate backwards over list of given type.
@@ -444,8 +444,8 @@ static inline void list_splice_tail_init(struct list_head *list,
  */
 #define list_for_each_entry_reverse(pos, head, member)			\
 	for (pos = list_entry((head)->prev, typeof(*pos), member);	\
-	     &pos->member != (head); 	\
-	     pos = list_entry(pos->member.prev, typeof(*pos), member))
+	     &pos->member != (head); 					\
+	     pos = list_prev_entry(pos, member))
 
 /**
  * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
@@ -468,9 +468,9 @@ static inline void list_splice_tail_init(struct list_head *list,
  * the current position.
  */
 #define list_for_each_entry_continue(pos, head, member) 		\
-	for (pos = list_entry(pos->member.next, typeof(*pos), member);	\
-	     &pos->member != (head);	\
-	     pos = list_entry(pos->member.next, typeof(*pos), member))
+	for (pos = list_next_entry(pos, member);			\
+	     &pos->member != (head);					\
+	     pos = list_next_entry(pos, member))
 
 /**
  * list_for_each_entry_continue_reverse - iterate backwards from the given point
@@ -482,9 +482,9 @@ static inline void list_splice_tail_init(struct list_head *list,
  * the current position.
  */
 #define list_for_each_entry_continue_reverse(pos, head, member)		\
-	for (pos = list_entry(pos->member.prev, typeof(*pos), member);	\
-	     &pos->member != (head);	\
-	     pos = list_entry(pos->member.prev, typeof(*pos), member))
+	for (pos = list_prev_entry(pos, member);			\
+	     &pos->member != (head);					\
+	     pos = list_prev_entry(pos, member))
 
 /**
  * list_for_each_entry_from - iterate over list of given type from the current point
@@ -495,8 +495,8 @@ static inline void list_splice_tail_init(struct list_head *list,
  * Iterate over list of given type, continuing from current position.
  */
 #define list_for_each_entry_from(pos, head, member) 			\
-	for (; &pos->member != (head);	\
-	     pos = list_entry(pos->member.next, typeof(*pos), member))
+	for (; &pos->member != (head);					\
+	     pos = list_next_entry(pos, member))
 
 /**
  * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
@@ -507,9 +507,9 @@ static inline void list_splice_tail_init(struct list_head *list,
  */
 #define list_for_each_entry_safe(pos, n, head, member)			\
 	for (pos = list_entry((head)->next, typeof(*pos), member),	\
-		n = list_entry(pos->member.next, typeof(*pos), member);	\
+		n = list_next_entry(pos, member);			\
 	     &pos->member != (head); 					\
-	     pos = n, n = list_entry(n->member.next, typeof(*n), member))
+	     pos = n, n = list_next_entry(n, member))
 
 /**
  * list_for_each_entry_safe_continue - continue list iteration safe against removal
@@ -522,10 +522,10 @@ static inline void list_splice_tail_init(struct list_head *list,
  * safe against removal of list entry.
  */
 #define list_for_each_entry_safe_continue(pos, n, head, member) 		\
-	for (pos = list_entry(pos->member.next, typeof(*pos), member), 		\
-		n = list_entry(pos->member.next, typeof(*pos), member);		\
+	for (pos = list_next_entry(pos, member), 				\
+		n = list_next_entry(pos, member);				\
 	     &pos->member != (head);						\
-	     pos = n, n = list_entry(n->member.next, typeof(*n), member))
+	     pos = n, n = list_next_entry(n, member))
 
 /**
  * list_for_each_entry_safe_from - iterate over list from current point safe against removal
@@ -538,9 +538,9 @@ static inline void list_splice_tail_init(struct list_head *list,
  * removal of list entry.
  */
 #define list_for_each_entry_safe_from(pos, n, head, member) 			\
-	for (n = list_entry(pos->member.next, typeof(*pos), member);		\
+	for (n = list_next_entry(pos, member);					\
 	     &pos->member != (head);						\
-	     pos = n, n = list_entry(n->member.next, typeof(*n), member))
+	     pos = n, n = list_next_entry(n, member))
 
 /**
  * list_for_each_entry_safe_reverse - iterate backwards over list safe against removal
@@ -554,9 +554,9 @@ static inline void list_splice_tail_init(struct list_head *list,
  */
 #define list_for_each_entry_safe_reverse(pos, n, head, member)		\
 	for (pos = list_entry((head)->prev, typeof(*pos), member),	\
-		n = list_entry(pos->member.prev, typeof(*pos), member);	\
+		n = list_prev_entry(pos, member);			\
 	     &pos->member != (head); 					\
-	     pos = n, n = list_entry(n->member.prev, typeof(*n), member))
+	     pos = n, n = list_prev_entry(n, member))
 
 /**
  * list_safe_reset_next - reset a stale list_for_each_entry_safe loop
@@ -571,7 +571,7 @@ static inline void list_splice_tail_init(struct list_head *list,
  * completing the current iteration of the loop body.
  */
 #define list_safe_reset_next(pos, n, member)				\
-	n = list_entry(pos->member.next, typeof(*pos), member)
+	n = list_next_entry(pos, member)
 
 /*
  * Double linked lists with a single pointer list head.
-- 
1.5.5.1

[PATCH 3/4] list: introduce list_last_entry(), use list_{first,last}_entry()

[Oleg Nesterov]

We alredy have list_first_entry(), it makes sense to also add
list_last_entry() for consistency. And we use both helpers in
in list_for_each_*().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 include/linux/list.h |   19 +++++++++++++++----
 1 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/include/linux/list.h b/include/linux/list.h
index c88a591..ef95941 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -362,6 +362,17 @@ static inline void list_splice_tail_init(struct list_head *list,
 	list_entry((ptr)->next, type, member)
 
 /**
+ * list_last_entry - get the last element from a list
+ * @ptr:	the list head to take the element from.
+ * @type:	the type of the struct this is embedded in.
+ * @member:	the name of the list_struct within the struct.
+ *
+ * Note, that list is expected to be not empty.
+ */
+#define list_last_entry(ptr, type, member) \
+	list_entry((ptr)->prev, type, member)
+
+/**
  * list_first_entry_or_null - get the first element from a list
  * @ptr:	the list head to take the element from.
  * @type:	the type of the struct this is embedded in.
@@ -432,7 +443,7 @@ static inline void list_splice_tail_init(struct list_head *list,
  * @member:	the name of the list_struct within the struct.
  */
 #define list_for_each_entry(pos, head, member)				\
-	for (pos = list_entry((head)->next, typeof(*pos), member);	\
+	for (pos = list_first_entry(head, typeof(*pos), member);	\
 	     &pos->member != (head);					\
 	     pos = list_next_entry(pos, member))
 
@@ -443,7 +454,7 @@ static inline void list_splice_tail_init(struct list_head *list,
  * @member:	the name of the list_struct within the struct.
  */
 #define list_for_each_entry_reverse(pos, head, member)			\
-	for (pos = list_entry((head)->prev, typeof(*pos), member);	\
+	for (pos = list_last_entry(head, typeof(*pos), member);		\
 	     &pos->member != (head); 					\
 	     pos = list_prev_entry(pos, member))
 
@@ -506,7 +517,7 @@ static inline void list_splice_tail_init(struct list_head *list,
  * @member:	the name of the list_struct within the struct.
  */
 #define list_for_each_entry_safe(pos, n, head, member)			\
-	for (pos = list_entry((head)->next, typeof(*pos), member),	\
+	for (pos = list_first_entry(head, typeof(*pos), member),	\
 		n = list_next_entry(pos, member);			\
 	     &pos->member != (head); 					\
 	     pos = n, n = list_next_entry(n, member))
@@ -553,7 +564,7 @@ static inline void list_splice_tail_init(struct list_head *list,
  * of list entry.
  */
 #define list_for_each_entry_safe_reverse(pos, n, head, member)		\
-	for (pos = list_entry((head)->prev, typeof(*pos), member),	\
+	for (pos = list_last_entry(head, typeof(*pos), member),		\
 		n = list_prev_entry(pos, member);			\
 	     &pos->member != (head); 					\
 	     pos = n, n = list_prev_entry(n, member))
-- 
1.5.5.1

[PATCH 4/4] debugfs: use list_next_entry() in debugfs_remove_recursive()

[Oleg Nesterov]

Change debugfs_remove_recursive() to use list_next_entry(child),
no changes in generated code.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 fs/debugfs/inode.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index c7c83ff..9c0444c 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -566,8 +566,7 @@ void debugfs_remove_recursive(struct dentry *dentry)
 	mutex_lock(&parent->d_inode->i_mutex);
 
 	if (child != dentry) {
-		next = list_entry(child->d_u.d_child.next, struct dentry,
-					d_u.d_child);
+		next = list_next_entry(child, d_u.d_child);
 		goto up;
 	}
 
-- 
1.5.5.1