Re: [PATCH for-next 2/3] RDMA/rtrs: Fix rxe_dealloc_pd warning

[Guoqing Jiang <guoqing.jiang@linux.dev>]

On 4/10/23 20:08, Leon Romanovsky wrote:
> On Mon, Apr 10, 2023 at 06:43:03AM +0000, Li Zhijian wrote:
>> The warning occurs when destroying PD whose reference count is not zero.
>>
>> Precodition: clt_path->s.con_num is 2.
>> So 2 cm connection will be created as below:
>> CPU0                                              CPU1
>> init_conns {                              |
>>    create_cm() // a. con[0] created        |
>>                                            |  a'. rtrs_clt_rdma_cm_handler() {
>>                                            |    rtrs_rdma_addr_resolved()
>>                                            |      create_con_cq_qp(con); << con[0]
>>                                            |  }
>>                                            | in this moment, refcnt of PD was increased to 2+
>>                                            |
>>    create_cm() // b. cid = 1, failed       |
>>      destroy_con_cq_qp()                   |
>>        rtrs_ib_dev_put()                   |
>>          dev_free()                        |
>>            ib_dealloc_pd(dev->ib_pd) << PD |
>>             is destroyed, but refcnt is    |
>>             still greater than 0           |
>> }
>>
>> Simply, Here we can avoid this warning by introducing conn own flag to
>> track if its cleanup should drop the PD.
>>
>> -----------------------------------------------
>>   rnbd_client L597: Mapping device /dev/nvme0n1 on session client, (access_mode: rw, nr_poll_queues: 0)
>>   ------------[ cut here ]------------
>>   WARNING: CPU: 0 PID: 26407 at drivers/infiniband/sw/rxe/rxe_pool.c:256 __rxe_cleanup+0x13a/0x170 [rdma_rxe]
>>   Modules linked in: rpcrdma rdma_ucm ib_iser rnbd_client libiscsi rtrs_client scsi_transport_iscsi rtrs_core rdma_cm iw_cm ib_cm crc32_generic rdma_rxe udp_tunnel ib_uverbs ib_core kmem device_dax nd_pmem dax_pmem nd_
>> vme crc32c_intel fuse nvme_core nfit libnvdimm dm_multipath scsi_dh_rdac scsi_dh_emc scsi_dh_alua dm_mirror dm_region_hash dm_log dm_mod
>>   CPU: 0 PID: 26407 Comm: rnbd-client.sh Kdump: loaded Not tainted 6.2.0-rc6-roce-flush+ #53
>>   Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
>>   RIP: 0010:__rxe_cleanup+0x13a/0x170 [rdma_rxe]
>>   Code: 45 84 e4 0f 84 5a ff ff ff 48 89 ef e8 5f 18 71 f9 84 c0 75 90 be c8 00 00 00 48 89 ef e8 be 89 1f fa 85 c0 0f 85 7b ff ff ff <0f> 0b 41 bc ea ff ff ff e9 71 ff ff ff e8 84 7f 1f fa e9 d0 fe ff
>>   RSP: 0018:ffffb09880b6f5f0 EFLAGS: 00010246
>>   RAX: 0000000000000000 RBX: ffff99401f15d6a8 RCX: 0000000000000000
>>   RDX: 0000000000000001 RSI: ffffffffbac8234b RDI: 00000000ffffffff
>>   RBP: ffff99401f15d6d0 R08: 0000000000000001 R09: 0000000000000001
>>   R10: 0000000000002d82 R11: 0000000000000000 R12: 0000000000000001
>>   R13: ffff994101eff208 R14: ffffb09880b6f6a0 R15: 00000000fffffe00
>>   FS:  00007fe113904740(0000) GS:ffff99413bc00000(0000) knlGS:0000000000000000
>>   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>   CR2: 00007ff6cde656c8 CR3: 000000001f108004 CR4: 00000000001706f0
>>   DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>   DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>   Call Trace:
>>    <TASK>
>>    rxe_dealloc_pd+0x16/0x20 [rdma_rxe]
>>    ib_dealloc_pd_user+0x4b/0x80 [ib_core]
>>    rtrs_ib_dev_put+0x79/0xd0 [rtrs_core]
>>    destroy_con_cq_qp+0x8a/0xa0 [rtrs_client]
>>    init_path+0x1e7/0x9a0 [rtrs_client]
>>    ? __pfx_autoremove_wake_function+0x10/0x10
>>    ? lock_is_held_type+0xd7/0x130
>>    ? rcu_read_lock_sched_held+0x43/0x80
>>    ? pcpu_alloc+0x3dd/0x7d0
>>    ? rtrs_clt_init_stats+0x18/0x40 [rtrs_client]
>>    rtrs_clt_open+0x24f/0x5a0 [rtrs_client]
>>    ? __pfx_rnbd_clt_link_ev+0x10/0x10 [rnbd_client]
>>    rnbd_clt_map_device+0x6a5/0xe10 [rnbd_client]
>>
>> Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
>> ---
>>   drivers/infiniband/ulp/rtrs/rtrs-clt.c | 4 ++++
>>   drivers/infiniband/ulp/rtrs/rtrs-clt.h | 1 +
>>   2 files changed, 5 insertions(+)
>>
>> diff --git a/drivers/infiniband/ulp/rtrs/rtrs-clt.c b/drivers/infiniband/ulp/rtrs/rtrs-clt.c
>> index c2065fc33a56..4c8f42e46e2f 100644
>> --- a/drivers/infiniband/ulp/rtrs/rtrs-clt.c
>> +++ b/drivers/infiniband/ulp/rtrs/rtrs-clt.c
>> @@ -1664,6 +1664,7 @@ static int create_con_cq_qp(struct rtrs_clt_con *con)
>>   			return -ENOMEM;
>>   		}
>>   		clt_path->s.dev_ref = 1;
>> +		con->has_dev = true;
>>   		query_fast_reg_mode(clt_path);
>>   		wr_limit = clt_path->s.dev->ib_dev->attrs.max_qp_wr;
>>   		/*
>> @@ -1690,6 +1691,7 @@ static int create_con_cq_qp(struct rtrs_clt_con *con)
>>   		wr_limit = clt_path->s.dev->ib_dev->attrs.max_qp_wr;
>>   		/* Shared between connections */
>>   		clt_path->s.dev_ref++;
> Without looking in the code, I would expect dev_ref from the line above
> to perform PD protection.

Agreed.

Thanks,
Guoqing