From b50e058746ba29f517e27299447831ab3d93f896 Mon Sep 17 00:00:00 2001 From: Zhu Yanjun Date: Mon, 3 Jun 2019 08:48:19 -0400 Subject: net: rds: fix memory leak when unload rds_rdma MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When KASAN is enabled, after several rds connections are created, then "rmmod rds_rdma" is run. The following will appear. " BUG rds_ib_incoming (Not tainted): Objects remaining in rds_ib_incoming on __kmem_cache_shutdown() Call Trace: dump_stack+0x71/0xab slab_err+0xad/0xd0 __kmem_cache_shutdown+0x17d/0x370 shutdown_cache+0x17/0x130 kmem_cache_destroy+0x1df/0x210 rds_ib_recv_exit+0x11/0x20 [rds_rdma] rds_ib_exit+0x7a/0x90 [rds_rdma] __x64_sys_delete_module+0x224/0x2c0 ? __ia32_sys_delete_module+0x2c0/0x2c0 do_syscall_64+0x73/0x190 entry_SYSCALL_64_after_hwframe+0x44/0xa9 " This is rds connection memory leak. The root cause is: When "rmmod rds_rdma" is run, rds_ib_remove_one will call rds_ib_dev_shutdown to drop the rds connections. rds_ib_dev_shutdown will call rds_conn_drop to drop rds connections as below. " rds_conn_path_drop(&conn->c_path[0], false); " In the above, destroy is set to false. void rds_conn_path_drop(struct rds_conn_path *cp, bool destroy) { atomic_set(&cp->cp_state, RDS_CONN_ERROR); rcu_read_lock(); if (!destroy && rds_destroy_pending(cp->cp_conn)) { rcu_read_unlock(); return; } queue_work(rds_wq, &cp->cp_down_w); rcu_read_unlock(); } In the above function, destroy is set to false. rds_destroy_pending is called. This does not move rds connections to ib_nodev_conns. So destroy is set to true to move rds connections to ib_nodev_conns. In rds_ib_unregister_client, flush_workqueue is called to make rds_wq finsh shutdown rds connections. The function rds_ib_destroy_nodev_conns is called to shutdown rds connections finally. Then rds_ib_recv_exit is called to destroy slab. void rds_ib_recv_exit(void) { kmem_cache_destroy(rds_ib_incoming_slab); kmem_cache_destroy(rds_ib_frag_slab); } The above slab memory leak will not occur again. >From tests, 256 rds connections [root@ca-dev14 ~]# time rmmod rds_rdma real 0m16.522s user 0m0.000s sys 0m8.152s 512 rds connections [root@ca-dev14 ~]# time rmmod rds_rdma real 0m32.054s user 0m0.000s sys 0m15.568s To rmmod rds_rdma with 256 rds connections, about 16 seconds are needed. And with 512 rds connections, about 32 seconds are needed. >From ftrace, when one rds connection is destroyed, " 19) | rds_conn_destroy [rds]() { 19) 7.782 us | rds_conn_path_drop [rds](); 15) | rds_shutdown_worker [rds]() { 15) | rds_conn_shutdown [rds]() { 15) 1.651 us | rds_send_path_reset [rds](); 15) 7.195 us | } 15) + 11.434 us | } 19) 2.285 us | rds_cong_remove_conn [rds](); 19) * 24062.76 us | } " So if many rds connections will be destroyed, this function rds_ib_destroy_nodev_conns uses most of time. Suggested-by: Håkon Bugge Signed-off-by: Zhu Yanjun Signed-off-by: David S. Miller --- net/rds/ib.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'net/rds/ib.c') diff --git a/net/rds/ib.c b/net/rds/ib.c index 2da9b75bad16..b8d581b779b2 100644 --- a/net/rds/ib.c +++ b/net/rds/ib.c @@ -87,7 +87,7 @@ static void rds_ib_dev_shutdown(struct rds_ib_device *rds_ibdev) spin_lock_irqsave(&rds_ibdev->spinlock, flags); list_for_each_entry(ic, &rds_ibdev->conn_list, ib_node) - rds_conn_drop(ic->conn); + rds_conn_path_drop(&ic->conn->c_path[0], true); spin_unlock_irqrestore(&rds_ibdev->spinlock, flags); } -- cgit v1.2.3-59-g8ed1b