linux-kernel - [RFC PATCH 1/2] add list_for_each_entry

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Date:   Fri, 20 Oct 2023 12:28:59 +0200
From:   Miklos Szeredi <mszeredi@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Takashi Iwai <tiwai@...e.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>,
        James Bottomley <James.Bottomley@...senpartnership.com>
Subject: [RFC PATCH 1/2] add list_for_each_entry_del()

Add a new list iteration macro that always takes the first element of the
list and removes it, until the list is empty.

Add a list_for_each_entry_del_init() variant too.

This is a common pattern.

Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
---
 include/linux/list.h | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/include/linux/list.h b/include/linux/list.h
index 164b4d0e9d2a..db23a9ee98f0 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -921,6 +921,35 @@ static inline size_t list_count_nodes(struct list_head *head)
 #define list_safe_reset_next(pos, n, member)				\
 	n = list_next_entry(pos, member)
 
+/**
+ * list_for_each_entry_del - iterate list and remove elements
+ * @pos:	the type * to use as a loop cursor.
+ * @head:	the head for your list.
+ * @member:	the name of the list_head within the struct.
+ *
+ * Delete first element from list before the iteration.  Iterate until
+ * the list is empty.
+ */
+#define list_for_each_entry_del(pos, head, member)			\
+	while (!list_empty(head) &&					\
+		({ pos = list_first_entry(head, typeof(*(pos)), member);\
+		   list_del(&(pos)->member); 1; }))
+
+/**
+ * list_for_each_entry_del_init - iterate list, remove and reinitialize elements
+ * @pos:	the type * to use as a loop cursor.
+ * @head:	the head for your list.
+ * @member:	the name of the list_head within the struct.
+ *
+ * Delete first element from list before the iteration using list_del_init().
+ * Iterate until the list is empty.
+ */
+#define list_for_each_entry_del_init(pos, head, member)			\
+	while (!list_empty(head) &&					\
+		({ pos = list_first_entry(head, typeof(*(pos)), member);\
+		   list_del_init(&(pos)->member); 1; }))
+
+
 /*
  * Double linked lists with a single pointer list head.
  * Mostly useful for hash tables where the two pointer list head is
-- 
2.41.0