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Subject[PATCH 08/13] list: add a new LRU list type
Date
From: Dave Chinner <dchinner@redhat.com>

Several subsystems use the same construct for LRU lists - a list
head, a spin lock and and item count. They also use exactly the same
code for adding and removing items from the LRU. Create a generic
type for these LRU lists.

This is the beginning of generic, node aware LRUs for shrinkers to
work with.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
include/linux/list_lru.h | 30 ++++++++++++
lib/Makefile | 3 +-
lib/list_lru.c | 112 ++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 144 insertions(+), 1 deletions(-)
create mode 100644 include/linux/list_lru.h
create mode 100644 lib/list_lru.c

diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
new file mode 100644
index 0000000..b112ca3
--- /dev/null
+++ b/include/linux/list_lru.h
@@ -0,0 +1,30 @@
+#ifndef _LRU_LIST_H
+#define _LRU_LIST_H 0
+
+#include <linux/list.h>
+
+struct list_lru {
+ spinlock_t lock;
+ struct list_head list;
+ long nr_items;
+};
+
+int list_lru_init(struct list_lru *lru);
+int list_lru_add(struct list_lru *lru, struct list_head *item);
+int list_lru_del(struct list_lru *lru, struct list_head *item);
+
+static inline long list_lru_count(struct list_lru *lru)
+{
+ return lru->nr_items;
+}
+
+typedef int (*list_lru_walk_cb)(struct list_head *item, spinlock_t *lock,
+ void *cb_arg);
+typedef void (*list_lru_dispose_cb)(struct list_head *dispose_list);
+
+long list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
+ void *cb_arg, long nr_to_walk);
+
+long list_lru_dispose_all(struct list_lru *lru, list_lru_dispose_cb dispose);
+
+#endif /* _LRU_LIST_H */
diff --git a/lib/Makefile b/lib/Makefile
index d5d175c..a08212f 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -12,7 +12,8 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
idr.o int_sqrt.o extable.o prio_tree.o \
sha1.o md5.o irq_regs.o reciprocal_div.o argv_split.o \
proportions.o prio_heap.o ratelimit.o show_mem.o \
- is_single_threaded.o plist.o decompress.o find_next_bit.o
+ is_single_threaded.o plist.o decompress.o find_next_bit.o \
+ list_lru.o

lib-$(CONFIG_MMU) += ioremap.o
lib-$(CONFIG_SMP) += cpumask.o
diff --git a/lib/list_lru.c b/lib/list_lru.c
new file mode 100644
index 0000000..8c18c63
--- /dev/null
+++ b/lib/list_lru.c
@@ -0,0 +1,112 @@
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/list_lru.h>
+
+int
+list_lru_add(
+ struct list_lru *lru,
+ struct list_head *item)
+{
+ spin_lock(&lru->lock);
+ if (list_empty(item)) {
+ list_add_tail(item, &lru->list);
+ lru->nr_items++;
+ spin_unlock(&lru->lock);
+ return 1;
+ }
+ spin_unlock(&lru->lock);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(list_lru_add);
+
+int
+list_lru_del(
+ struct list_lru *lru,
+ struct list_head *item)
+{
+ spin_lock(&lru->lock);
+ if (!list_empty(item)) {
+ list_del_init(item);
+ lru->nr_items--;
+ spin_unlock(&lru->lock);
+ return 1;
+ }
+ spin_unlock(&lru->lock);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(list_lru_del);
+
+long
+list_lru_walk(
+ struct list_lru *lru,
+ list_lru_walk_cb isolate,
+ void *cb_arg,
+ long nr_to_walk)
+{
+ struct list_head *item, *n;
+ long removed = 0;
+restart:
+ spin_lock(&lru->lock);
+ list_for_each_safe(item, n, &lru->list) {
+ int ret;
+
+ if (nr_to_walk-- < 0)
+ break;
+
+ ret = isolate(item, &lru->lock, cb_arg);
+ switch (ret) {
+ case 0: /* item removed from list */
+ lru->nr_items--;
+ removed++;
+ break;
+ case 1: /* item referenced, give another pass */
+ list_move_tail(item, &lru->list);
+ break;
+ case 2: /* item cannot be locked, skip */
+ break;
+ case 3: /* item not freeable, lock dropped */
+ goto restart;
+ default:
+ BUG();
+ }
+ }
+ spin_unlock(&lru->lock);
+ return removed;
+}
+EXPORT_SYMBOL_GPL(list_lru_walk);
+
+long
+list_lru_dispose_all(
+ struct list_lru *lru,
+ list_lru_dispose_cb dispose)
+{
+ long disposed = 0;
+ LIST_HEAD(dispose_list);
+
+ spin_lock(&lru->lock);
+ while (!list_empty(&lru->list)) {
+ list_splice_init(&lru->list, &dispose_list);
+ disposed += lru->nr_items;
+ lru->nr_items = 0;
+ spin_unlock(&lru->lock);
+
+ dispose(&dispose_list);
+
+ spin_lock(&lru->lock);
+ }
+ spin_unlock(&lru->lock);
+ return disposed;
+}
+
+int
+list_lru_init(
+ struct list_lru *lru)
+{
+ spin_lock_init(&lru->lock);
+ INIT_LIST_HEAD(&lru->list);
+ lru->nr_items = 0;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(list_lru_init);
--
1.7.5.4


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