[Devel] [PATCH RHEL7 COMMIT] mm: Add rcu field to struct list_lru_memcg

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-514.26.1.vz7.35.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-514.26.1.vz7.35.5
------>
commit b3b3ea1125f07f57ea0f95b29ad368934cc7bb53
Author: Kirill Tkhai <ktkhai at virtuozzo.com>
Date:   Thu Aug 31 18:25:19 2017 +0300

    mm: Add rcu field to struct list_lru_memcg
    
    Patchset description:
    Make count list_lru_one::nr_items lockless
    
    This series aims to improve scalability of list_lru shrinking
    and to make list_lru_count_one() working more effective.
    
    Kirill Tkhai (3):
          mm: Add rcu field to struct list_lru_memcg
          mm: Make list_lru_node::memcg_lrus RCU protected
          mm: Count list_lru_one::nr_items lockless
    
    https://jira.sw.ru/browse/PSBM-69296
    
    =====================
    This patch description:
    
    This patch adds the new field and teaches kmalloc()
    to allocate memory for it.
    
    Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
    Acked-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
---
 include/linux/list_lru.h | 1 +
 mm/list_lru.c            | 7 ++++---
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
index 2a6b994..7bf4251 100644
--- a/include/linux/list_lru.h
+++ b/include/linux/list_lru.h
@@ -31,6 +31,7 @@ struct list_lru_one {
 };
 
 struct list_lru_memcg {
+	struct rcu_head		rcu;
 	/* array of per cgroup lists, indexed by memcg_cache_id */
 	struct list_lru_one	*lru[0];
 };
diff --git a/mm/list_lru.c b/mm/list_lru.c
index 84b4c21..cb53462 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -313,7 +313,8 @@ static int memcg_init_list_lru_node(struct list_lru_node *nlru)
 {
 	int size = memcg_nr_cache_ids;
 
-	nlru->memcg_lrus = kmalloc(size * sizeof(void *), GFP_KERNEL);
+	nlru->memcg_lrus = kmalloc(sizeof(struct list_lru_memcg) +
+				   size * sizeof(void *), GFP_KERNEL);
 	if (!nlru->memcg_lrus)
 		return -ENOMEM;
 
@@ -339,7 +340,7 @@ static int memcg_update_list_lru_node(struct list_lru_node *nlru,
 	BUG_ON(old_size > new_size);
 
 	old = nlru->memcg_lrus;
-	new = kmalloc(new_size * sizeof(void *), GFP_KERNEL);
+	new = kmalloc(sizeof(*new) + new_size * sizeof(void *), GFP_KERNEL);
 	if (!new)
 		return -ENOMEM;
 
@@ -348,7 +349,7 @@ static int memcg_update_list_lru_node(struct list_lru_node *nlru,
 		return -ENOMEM;
 	}
 
-	memcpy(new, old, old_size * sizeof(void *));
+	memcpy(&new->lru, &old->lru, old_size * sizeof(void *));
 
 	/*
 	 * The lock guarantees that we won't race with a reader