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Subject[PATCH v2 19/22] mm: handle lruvec relock in memory controller
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Date
Carefully relock lruvec lru lock at page memory cgroup change.

* Stabilize PageLRU() sign with __wait_lruvec_unlock(old_lruvec)
It must be called between each pc->mem_cgroup change and
page putback into new lruvec, otherwise someone else can lock old lruvec and
see PageLRU(), while page already moved into other lruvec.
* In free_pn_rcu() wait for lruvec lock release.
Locking primitives keep lruvec pointer after successful lock held.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
---
mm/memcontrol.c | 36 ++++++++++++++++++++++++++++--------
1 files changed, 28 insertions(+), 8 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 40e1a66..69763da 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2368,6 +2368,7 @@ static int mem_cgroup_move_account(struct page *page,
unsigned long flags;
int ret;
bool anon = PageAnon(page);
+ struct lruvec *old_lruvec;

VM_BUG_ON(from == to);
VM_BUG_ON(PageLRU(page));
@@ -2397,12 +2398,24 @@ static int mem_cgroup_move_account(struct page *page,
preempt_enable();
}
mem_cgroup_charge_statistics(from, anon, -nr_pages);
+
+ /* charge keep old lruvec alive */
+ old_lruvec = page_lruvec(page);
+
+ /* caller should have done css_get */
+ pc->mem_cgroup = to;
+
+ /*
+ * Stabilize PageLRU() sing for old_lruvec lock holder.
+ * Do not putback page while someone hold old_lruvec lock,
+ * otherwise it can think it catched page in old_lruvec lru.
+ */
+ __wait_lruvec_unlock(old_lruvec);
+
if (uncharge)
/* This is not "cancel", but cancel_charge does all we need. */
__mem_cgroup_cancel_charge(from, nr_pages);

- /* caller should have done css_get */
- pc->mem_cgroup = to;
mem_cgroup_charge_statistics(to, anon, nr_pages);
/*
* We charges against "to" which may not have any tasks. Then, "to"
@@ -2528,7 +2541,6 @@ __mem_cgroup_commit_charge_lrucare(struct page *page, struct mem_cgroup *memcg,
enum charge_type ctype)
{
struct page_cgroup *pc = lookup_page_cgroup(page);
- struct zone *zone = page_zone(page);
struct lruvec *lruvec;
unsigned long flags;
bool removed = false;
@@ -2538,20 +2550,19 @@ __mem_cgroup_commit_charge_lrucare(struct page *page, struct mem_cgroup *memcg,
* is already on LRU. It means the page may on some other page_cgroup's
* LRU. Take care of it.
*/
- spin_lock_irqsave(&zone->lru_lock, flags);
+ lruvec = lock_page_lruvec(page, &flags);
if (PageLRU(page)) {
- lruvec = page_lruvec(page);
del_page_from_lru_list(lruvec, page, page_lru(page));
ClearPageLRU(page);
removed = true;
}
__mem_cgroup_commit_charge(memcg, page, 1, pc, ctype);
if (removed) {
- lruvec = page_lruvec(page);
+ lruvec = __relock_page_lruvec(lruvec, page);
add_page_to_lru_list(lruvec, page, page_lru(page));
SetPageLRU(page);
}
- spin_unlock_irqrestore(&zone->lru_lock, flags);
+ unlock_lruvec(lruvec, &flags);
}

int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
@@ -4648,7 +4659,16 @@ static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *memcg, int node)

static void free_mem_cgroup_per_zone_info(struct mem_cgroup *memcg, int node)
{
- kfree(memcg->info.nodeinfo[node]);
+ struct mem_cgroup_per_node *pn = memcg->info.nodeinfo[node];
+ int zone;
+
+ if (!pn)
+ return;
+
+ for (zone = 0; zone < MAX_NR_ZONES; zone++)
+ wait_lruvec_unlock(&pn->zoneinfo[zone].lruvec);
+
+ kfree(pn);
}

static struct mem_cgroup *mem_cgroup_alloc(void)


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