Add plist_rotate(), which moves the specified plist_node after
all other same-priority plist_nodes in the list.
This is needed by swap, which has a plist of swap_info_structs
and needs to use each same-priority swap_info_struct equally.
Also add plist_test_rotate() test function, for use by plist_test()
to test plist_rotate() function.
Signed-off-by: Dan Streetman <ddstreet@xxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
This patch is new to this patch set, and it's required by the next patch,
which needs a way to move a plist entry to the end of all following
same-priority entries. This is possible to do manually instead of adding
a new plist function, but having a common plist function instead of code
specific only to swap seems preferable.
include/linux/plist.h | 2 ++
lib/plist.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 50 insertions(+)
diff --git a/include/linux/plist.h b/include/linux/plist.h
index c815491..06e6925 100644
--- a/include/linux/plist.h
+++ b/include/linux/plist.h
@@ -141,6 +141,8 @@ static inline void plist_node_init(struct plist_node *node, int prio)
extern void plist_add(struct plist_node *node, struct plist_head *head);
extern void plist_del(struct plist_node *node, struct plist_head *head);
+extern void plist_rotate(struct plist_node *node, struct plist_head *head);
+
/**
* plist_for_each - iterate over the plist
* @pos: the type * to use as a loop counter
diff --git a/lib/plist.c b/lib/plist.c
index 1ebc95f..a8b54e5 100644
--- a/lib/plist.c
+++ b/lib/plist.c
@@ -134,6 +134,42 @@ void plist_del(struct plist_node *node, struct plist_head *head)
plist_check_head(head);
}
+/**
+ * plist_rotate - Rotate @node to end of same-prio entries.
+ *
+ * @node: &struct plist_node pointer - entry to be moved
+ * @head: &struct plist_head pointer - list head
+ */
+void plist_rotate(struct plist_node *node, struct plist_head *head)
+{
+ struct plist_node *next;
+ struct list_head *next_node_list = &head->node_list;
+
+ plist_check_head(head);
+ BUG_ON(plist_head_empty(head));
+ BUG_ON(plist_node_empty(node));
+
+ if (node == plist_last(head))
+ return;
+
+ next = plist_next(node);
+
+ if (node->prio != next->prio)
+ return;
+
+ plist_del(node, head);
+
+ plist_for_each_continue(next, head) {
+ if (node->prio != next->prio) {
+ next_node_list = &next->node_list;
+ break;
+ }
+ }
+ list_add_tail(&node->node_list, next_node_list);
+
+ plist_check_head(head);
+}
+
#ifdef CONFIG_DEBUG_PI_LIST
#include <linux/sched.h>
#include <linux/module.h>
@@ -170,6 +206,14 @@ static void __init plist_test_check(int nr_expect)
BUG_ON(prio_pos->prio_list.next != &first->prio_list);
}
+static void __init plist_test_rotate(struct plist_node *node)
+{
+ plist_rotate(node, &test_head);
+
+ if (node != plist_last(&test_head))
+ BUG_ON(node->prio == plist_next(node)->prio);
+}
+
static int __init plist_test(void)
{
int nr_expect = 0, i, loop;
@@ -193,6 +237,10 @@ static int __init plist_test(void)
nr_expect--;
}
plist_test_check(nr_expect);
+ if (!plist_node_empty(test_node + i)) {
+ plist_test_rotate(test_node + i);
+ plist_test_check(nr_expect);
+ }
}
for (i = 0; i < ARRAY_SIZE(test_node); i++) {
--
1.8.3.1
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