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[PATCH 1/6] list: introduce list_last_entry_or_null()

To: linux-kernel@xxxxxxxxxxxxxxx
Subject: [PATCH 1/6] list: introduce list_last_entry_or_null()
From: Jeff Liu <jeff.liu@xxxxxxxxxx>
Date: Fri, 15 Nov 2013 12:31:15 +0800
Cc: akpm@xxxxxxxxxxxxxxxxxxxx, "xfs@xxxxxxxxxxx" <xfs@xxxxxxxxxxx>, cluster-devel@xxxxxxxxxx, linux-mtd@xxxxxxxxxxxxxxxxxxx, jfs-discussion@xxxxxxxxxxxxxxxxxxxxx, oleg@xxxxxxxxxx, jiri@xxxxxxxxxxx, gregkh@xxxxxxxxxxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0
From: Jie Liu <jeff.liu@xxxxxxxxxx>

Introduce a trivial helper list_last_entry_or_null() to fetch the
last entry from a list, return NULL if the list is empty.

Signed-off-by: Jie Liu <jeff.liu@xxxxxxxxxx>
---
 include/linux/list.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/include/linux/list.h b/include/linux/list.h
index ef95941..3337249 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -384,6 +384,17 @@ static inline void list_splice_tail_init(struct list_head 
*list,
        (!list_empty(ptr) ? list_first_entry(ptr, type, member) : NULL)
 
 /**
+ * list_last_entry_or_null - 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 if the list is empty, it returns NULL.
+ */
+#define list_last_entry_or_null(ptr, type, member) \
+       (!list_empty(ptr) ? list_last_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.
-- 
1.8.3.2

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