On 11/15, Oleg Nesterov wrote:
>
> But probably list_last_entry() makes sense in the "else" branch,
> athough this is minor.
>
>
> Off-topic. Not sure this really makes sense, but I was thinking about
>
> list_get_first(pos, head, member) \
> ((pos) = list_first_entry(head, typeof(*pos), member))
>
> and list_get_first() last of course. The obvious advantage is that
> compared to
>
> tr = list_last_entry(sdp->sd_ail1_list, struct gfs2_trans, tr_list);
>
> above you do not need to type "struct gfs2_trans",
>
> list_get_last(tr, sdp->sd_ail1_list, tr_list);
>
> looks a bit better.
And list.h can use it too.
So how about the patch below? I can't decide whether it cleanups or
uglfies the code, I do not trust my taste ;) But to me it looks a
bit better this way.
Oleg.
--
diff --git a/include/linux/list.h b/include/linux/list.h
index ef95941..f52aba8 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -372,6 +372,12 @@ static inline void list_splice_tail_init(struct list_head
*list,
#define list_last_entry(ptr, type, member) \
list_entry((ptr)->prev, type, member)
+#define list_get_first(pos, head, member) \
+ ((pos) = list_first_entry(head, typeof(*(pos)), member))
+
+#define list_get_last(pos, head, member) \
+ ((pos) = list_last_entry(head, typeof(*(pos)), member))
+
/**
* list_first_entry_or_null - get the first element from a list
* @ptr: the list head to take the element from.
@@ -443,7 +449,7 @@ 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_first_entry(head, typeof(*pos), member); \
+ for (list_get_first(pos, head, member); \
&pos->member != (head); \
pos = list_next_entry(pos, member))
@@ -454,7 +460,7 @@ 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_last_entry(head, typeof(*pos), member); \
+ for (list_get_last(pos, head, member); \
&pos->member != (head); \
pos = list_prev_entry(pos, member))
@@ -517,7 +523,7 @@ 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_first_entry(head, typeof(*pos), member), \
+ for (list_get_first(pos, head, member), \
n = list_next_entry(pos, member); \
&pos->member != (head); \
pos = n, n = list_next_entry(n, member))
@@ -564,7 +570,7 @@ 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_last_entry(head, typeof(*pos), member), \
+ for (list_get_last(pos, head, member), \
n = list_prev_entry(pos, member); \
&pos->member != (head); \
pos = n, n = list_prev_entry(n, member))
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