From e130816164e244b692921de49771eeb28205152d Mon Sep 17 00:00:00 2001
From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Date: Thu, 15 Oct 2020 20:11:31 -0700
Subject: [PATCH] include/linux/list.h: add a macro to test if entry is pointing to the head
Git-commit: e130816164e244b692921de49771eeb28205152d
Patch-mainline: v5.10-rc1
References: git-fixes
Add a macro to test if entry is pointing to the head of the list which is
useful in cases like:
list_for_each_entry(pos, &head, member) {
if (cond)
break;
}
if (list_entry_is_head(pos, &head, member))
return -ERRNO;
that allows to avoid additional variable to be added to track if loop has
not been stopped in the middle.
While here, convert list_for_each_entry*() family of macros to use a new one.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Cezary Rojewski <cezary.rojewski@intel.com>
Link: https://lkml.kernel.org/r/20200929134342.51489-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
include/linux/list.h | 29 +++++++++++++++++++----------
1 file changed, 19 insertions(+), 10 deletions(-)
diff --git a/include/linux/list.h b/include/linux/list.h
index 0d0d17a10d25..a18c87b63376 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -609,6 +609,15 @@ static inline void list_splice_tail_init(struct list_head *list,
pos != (head); \
pos = n, n = pos->prev)
+/**
+ * list_entry_is_head - test if the entry points to the head of the list
+ * @pos: the type * to cursor
+ * @head: the head for your list.
+ * @member: the name of the list_head within the struct.
+ */
+#define list_entry_is_head(pos, head, member) \
+ (&pos->member == (head))
+
/**
* list_for_each_entry - iterate over list of given type
* @pos: the type * to use as a loop cursor.
@@ -617,7 +626,7 @@ static inline void list_splice_tail_init(struct list_head *list,
*/
#define list_for_each_entry(pos, head, member) \
for (pos = list_first_entry(head, typeof(*pos), member); \
- &pos->member != (head); \
+ !list_entry_is_head(pos, head, member); \
pos = list_next_entry(pos, member))
/**
@@ -628,7 +637,7 @@ static inline void list_splice_tail_init(struct list_head *list,
*/
#define list_for_each_entry_reverse(pos, head, member) \
for (pos = list_last_entry(head, typeof(*pos), member); \
- &pos->member != (head); \
+ !list_entry_is_head(pos, head, member); \
pos = list_prev_entry(pos, member))
/**
@@ -653,7 +662,7 @@ static inline void list_splice_tail_init(struct list_head *list,
*/
#define list_for_each_entry_continue(pos, head, member) \
for (pos = list_next_entry(pos, member); \
- &pos->member != (head); \
+ !list_entry_is_head(pos, head, member); \
pos = list_next_entry(pos, member))
/**
@@ -667,7 +676,7 @@ static inline void list_splice_tail_init(struct list_head *list,
*/
#define list_for_each_entry_continue_reverse(pos, head, member) \
for (pos = list_prev_entry(pos, member); \
- &pos->member != (head); \
+ !list_entry_is_head(pos, head, member); \
pos = list_prev_entry(pos, member))
/**
@@ -679,7 +688,7 @@ 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); \
+ for (; !list_entry_is_head(pos, head, member); \
pos = list_next_entry(pos, member))
/**
@@ -692,7 +701,7 @@ static inline void list_splice_tail_init(struct list_head *list,
* Iterate backwards over list of given type, continuing from current position.
*/
#define list_for_each_entry_from_reverse(pos, head, member) \
- for (; &pos->member != (head); \
+ for (; !list_entry_is_head(pos, head, member); \
pos = list_prev_entry(pos, member))
/**
@@ -705,7 +714,7 @@ static inline void list_splice_tail_init(struct list_head *list,
#define list_for_each_entry_safe(pos, n, head, member) \
for (pos = list_first_entry(head, typeof(*pos), member), \
n = list_next_entry(pos, member); \
- &pos->member != (head); \
+ !list_entry_is_head(pos, head, member); \
pos = n, n = list_next_entry(n, member))
/**
@@ -721,7 +730,7 @@ static inline void list_splice_tail_init(struct list_head *list,
#define list_for_each_entry_safe_continue(pos, n, head, member) \
for (pos = list_next_entry(pos, member), \
n = list_next_entry(pos, member); \
- &pos->member != (head); \
+ !list_entry_is_head(pos, head, member); \
pos = n, n = list_next_entry(n, member))
/**
@@ -736,7 +745,7 @@ static inline void list_splice_tail_init(struct list_head *list,
*/
#define list_for_each_entry_safe_from(pos, n, head, member) \
for (n = list_next_entry(pos, member); \
- &pos->member != (head); \
+ !list_entry_is_head(pos, head, member); \
pos = n, n = list_next_entry(n, member))
/**
@@ -752,7 +761,7 @@ 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_last_entry(head, typeof(*pos), member), \
n = list_prev_entry(pos, member); \
- &pos->member != (head); \
+ !list_entry_is_head(pos, head, member); \
pos = n, n = list_prev_entry(n, member))
/**
--
2.26.2