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

["Zhijian Li (Fujitsu)" <lizhijian@fujitsu.com>]

On 11/04/2023 20:26, Leon Romanovsky wrote:
> On Tue, Apr 11, 2023 at 02:43:46AM +0000, Zhijian Li (Fujitsu) wrote:
>>
>>
>> On 10/04/2023 21:10, Guoqing Jiang wrote:
>>>
>>>
>>> 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.
>>
>> Sorry, i didn't get your point. Do you mean something like this:
>>
>> +		con->has_dev = true;
>>    		clt_path->s.dev_ref++;
> 
> No, my point was that clt_path->s.dev_ref > 0 means that has_dev is
> equal to true, and dev_ref is supposed to protect from early PD
> destruction.
> 


> +       if (!con->has_dev)
> +               return;

We have already done such protection VVVV

>         if (clt_path->s.dev_ref && !--clt_path->s.dev_ref) {  <<< each cleanup will decrease clt_path->s.dev_ref
>                 rtrs_ib_dev_put(clt_path->s.dev);             <<< when it becomes to 0, PD will be destructed.
>                 clt_path->s.dev = NULL;


But they are not equal, clt_path->s.dev_ref could be shared by multiple connections.
So in the case con[0] successed and con[1] failed(clt_path->s.dev_ref is 1),
the con[1]'s cleanup path(destroy_con_cq_qp) will destroy PD while conn[0] still associates this PD.


Thanks
Zhijian

> Thanks
> 
>>
>>
>>
>> Thanks
>> Zhijian
>>
>>>
>>> Thanks,
>>> Guoqing