[PATCH v2 4/5] mm: make memcg visible to lru walker isolation function

[Yafang Shao <laoar.shao@gmail.com>]

The lru walker isolation function may use this memcg to do something, e.g.
the inode isolatation function will use the memcg to do inode protection in
followup patch. So make memcg visible to the lru walker isolation function.

Something should be emphasized in this patch is it replaces
for_each_memcg_cache_index() with for_each_mem_cgroup() in
list_lru_walk_node(). Because there's a gap between these two MACROs that
for_each_mem_cgroup() depends on CONFIG_MEMCG while the other one depends
on CONFIG_MEMCG_KMEM. But as list_lru_memcg_aware() returns false if
CONFIG_MEMCG_KMEM is not configured, it is safe to this replacement.

Cc: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 include/linux/memcontrol.h | 21 +++++++++++++++++++++
 mm/list_lru.c              | 22 ++++++++++++----------
 mm/memcontrol.c            | 15 ---------------
 3 files changed, 33 insertions(+), 25 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 1a315c7..f36ada9 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -449,6 +449,21 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *,
 int mem_cgroup_scan_tasks(struct mem_cgroup *,
 			  int (*)(struct task_struct *, void *), void *);
 
+/*
+ * Iteration constructs for visiting all cgroups (under a tree).  If
+ * loops are exited prematurely (break), mem_cgroup_iter_break() must
+ * be used for reference counting.
+ */
+#define for_each_mem_cgroup_tree(iter, root)		\
+	for (iter = mem_cgroup_iter(root, NULL, NULL);	\
+	     iter != NULL;				\
+	     iter = mem_cgroup_iter(root, iter, NULL))
+
+#define for_each_mem_cgroup(iter)			\
+	for (iter = mem_cgroup_iter(NULL, NULL, NULL);	\
+	     iter != NULL;				\
+	     iter = mem_cgroup_iter(NULL, iter, NULL))
+
 static inline unsigned short mem_cgroup_id(struct mem_cgroup *memcg)
 {
 	if (mem_cgroup_disabled())
@@ -949,6 +964,12 @@ static inline int mem_cgroup_scan_tasks(struct mem_cgroup *memcg,
 	return 0;
 }
 
+#define for_each_mem_cgroup_tree(iter)		\
+	for (iter = NULL; iter; )
+
+#define for_each_mem_cgroup(iter)		\
+	for (iter = NULL; iter; )
+
 static inline unsigned short mem_cgroup_id(struct mem_cgroup *memcg)
 {
 	return 0;
diff --git a/mm/list_lru.c b/mm/list_lru.c
index 0f1f6b0..536830d 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -207,11 +207,11 @@ unsigned long list_lru_count_node(struct list_lru *lru, int nid)
 EXPORT_SYMBOL_GPL(list_lru_count_node);
 
 static unsigned long
-__list_lru_walk_one(struct list_lru_node *nlru, int memcg_idx,
+__list_lru_walk_one(struct list_lru_node *nlru, struct mem_cgroup *memcg,
 		    list_lru_walk_cb isolate, void *cb_arg,
 		    unsigned long *nr_to_walk)
 {
-
+	int memcg_idx = memcg_cache_id(memcg);
 	struct list_lru_one *l;
 	struct list_head *item, *n;
 	unsigned long isolated = 0;
@@ -273,7 +273,7 @@ unsigned long list_lru_count_node(struct list_lru *lru, int nid)
 	unsigned long ret;
 
 	spin_lock(&nlru->lock);
-	ret = __list_lru_walk_one(nlru, memcg_cache_id(memcg), isolate, cb_arg,
+	ret = __list_lru_walk_one(nlru, memcg, isolate, cb_arg,
 				  nr_to_walk);
 	spin_unlock(&nlru->lock);
 	return ret;
@@ -289,7 +289,7 @@ unsigned long list_lru_count_node(struct list_lru *lru, int nid)
 	unsigned long ret;
 
 	spin_lock_irq(&nlru->lock);
-	ret = __list_lru_walk_one(nlru, memcg_cache_id(memcg), isolate, cb_arg,
+	ret = __list_lru_walk_one(nlru, memcg, isolate, cb_arg,
 				  nr_to_walk);
 	spin_unlock_irq(&nlru->lock);
 	return ret;
@@ -299,17 +299,15 @@ unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
 				 list_lru_walk_cb isolate, void *cb_arg,
 				 unsigned long *nr_to_walk)
 {
+	struct mem_cgroup *memcg;
 	long isolated = 0;
-	int memcg_idx;
 
-	isolated += list_lru_walk_one(lru, nid, NULL, isolate, cb_arg,
-				      nr_to_walk);
-	if (*nr_to_walk > 0 && list_lru_memcg_aware(lru)) {
-		for_each_memcg_cache_index(memcg_idx) {
+	if (list_lru_memcg_aware(lru)) {
+		for_each_mem_cgroup(memcg) {
 			struct list_lru_node *nlru = &lru->node[nid];
 
 			spin_lock(&nlru->lock);
-			isolated += __list_lru_walk_one(nlru, memcg_idx,
+			isolated += __list_lru_walk_one(nlru, memcg,
 							isolate, cb_arg,
 							nr_to_walk);
 			spin_unlock(&nlru->lock);
@@ -317,7 +315,11 @@ unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
 			if (*nr_to_walk <= 0)
 				break;
 		}
+	} else {
+		isolated += list_lru_walk_one(lru, nid, NULL, isolate, cb_arg,
+					      nr_to_walk);
 	}
+
 	return isolated;
 }
 EXPORT_SYMBOL_GPL(list_lru_walk_node);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2e78931..2fc2bf4 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -222,21 +222,6 @@ enum res_type {
 /* Used for OOM nofiier */
 #define OOM_CONTROL		(0)
 
-/*
- * Iteration constructs for visiting all cgroups (under a tree).  If
- * loops are exited prematurely (break), mem_cgroup_iter_break() must
- * be used for reference counting.
- */
-#define for_each_mem_cgroup_tree(iter, root)		\
-	for (iter = mem_cgroup_iter(root, NULL, NULL);	\
-	     iter != NULL;				\
-	     iter = mem_cgroup_iter(root, iter, NULL))
-
-#define for_each_mem_cgroup(iter)			\
-	for (iter = mem_cgroup_iter(NULL, NULL, NULL);	\
-	     iter != NULL;				\
-	     iter = mem_cgroup_iter(NULL, iter, NULL))
-
 static inline bool should_force_charge(void)
 {
 	return tsk_is_oom_victim(current) || fatal_signal_pending(current) ||
-- 
1.8.3.1