[PATCH v2] kvfree_rcu: Release page cache under memory pressure

[qiang . zhang]

From: Zqiang <qiang.zh...@windriver.com>

Add free per-cpu existing krcp's page cache operation, when
the system is under memory pressure.

Signed-off-by: Zqiang <qiang.zh...@windriver.com>
---
 kernel/rcu/tree.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index c1ae1e52f638..ec098910d80b 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3571,17 +3571,40 @@ void kvfree_call_rcu(struct rcu_head *head, 
rcu_callback_t func)
 }
 EXPORT_SYMBOL_GPL(kvfree_call_rcu);
 
+static int free_krc_page_cache(struct kfree_rcu_cpu *krcp)
+{
+       unsigned long flags;
+       struct kvfree_rcu_bulk_data *bnode;
+       int i;
+
+       for (i = 0; i < rcu_min_cached_objs; i++) {
+               raw_spin_lock_irqsave(&krcp->lock, flags);
+               bnode = get_cached_bnode(krcp);
+               raw_spin_unlock_irqrestore(&krcp->lock, flags);
+               if (!bnode)
+                       break;
+               free_page((unsigned long)bnode);
+       }
+
+       return i;
+}
+
 static unsigned long
 kfree_rcu_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
 {
        int cpu;
        unsigned long count = 0;
+       unsigned long flags;
 
        /* Snapshot count of all CPUs */
        for_each_possible_cpu(cpu) {
                struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
 
                count += READ_ONCE(krcp->count);
+
+               raw_spin_lock_irqsave(&krcp->lock, flags);
+               count += krcp->nr_bkv_objs;
+               raw_spin_unlock_irqrestore(&krcp->lock, flags);
        }
 
        return count;
@@ -3598,6 +3621,8 @@ kfree_rcu_shrink_scan(struct shrinker *shrink, struct 
shrink_control *sc)
                struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
 
                count = krcp->count;
+               count += free_krc_page_cache(krcp);
+
                raw_spin_lock_irqsave(&krcp->lock, flags);
                if (krcp->monitor_todo)
                        kfree_rcu_drain_unlock(krcp, flags);
-- 
2.17.1