[PATCH v2] rcu/kvfree: Prevents cache growing when the backoff_page_cache_fill is set

[Zqiang]

Currently, in kfree_rcu_shrink_scan(), the drain_page_cache() is
executed before kfree_rcu_monitor() to drain page cache, if the bnode
structure's->gp_snap has done, the kvfree_rcu_bulk() will fill the
page cache again in kfree_rcu_monitor(), this commit add a check
for krcp structure's->backoff_page_cache_fill in put_cached_bnode(),
if the krcp structure's->backoff_page_cache_fill is set, prevent page
cache growing.

Signed-off-by: Zqiang <qiang1.zhang@xxxxxxxxx>
---
 kernel/rcu/tree.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 9cc0a7766fd2..f25430ae1936 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2907,6 +2907,8 @@ static inline bool
 put_cached_bnode(struct kfree_rcu_cpu *krcp,
 	struct kvfree_rcu_bulk_data *bnode)
 {
+	if (atomic_read(&krcp->backoff_page_cache_fill))
+		return false;
 	// Check the limit.
 	if (krcp->nr_bkv_objs >= rcu_min_cached_objs)
 		return false;
-- 
2.32.0