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Date:   Mon, 10 Apr 2023 15:08:09 +0300
From:   Leon Romanovsky <leon@kernel.org>
To:     Li Zhijian <lizhijian@fujitsu.com>
Cc:     haris.iqbal@ionos.com, jinpu.wang@ionos.com, jgg@ziepe.ca,
        linux-rdma@vger.kernel.org, guoqing.jiang@linux.dev,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH for-next 2/3] RDMA/rtrs: Fix rxe_dealloc_pd warning
Message-ID: <20230410120809.GN182481@unreal>
References: <1681108984-2-1-git-send-email-lizhijian@fujitsu.com>
 <1681108984-2-3-git-send-email-lizhijian@fujitsu.com>
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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.

> +		con->has_dev = true;
>  		max_send_wr = min_t(int, wr_limit,
>  			      /* QD * (REQ + RSP + FR REGS or INVS) + drain */
>  			      clt_path->queue_depth * 3 + 1);
> @@ -1742,6 +1744,8 @@ static void destroy_con_cq_qp(struct rtrs_clt_con *con)
>  		con->rsp_ius = NULL;
>  		con->queue_num = 0;
>  	}
> +	if (!con->has_dev)
> +		return;
>  	if (clt_path->s.dev_ref && !--clt_path->s.dev_ref) {
>  		rtrs_ib_dev_put(clt_path->s.dev);
>  		clt_path->s.dev = NULL;
> diff --git a/drivers/infiniband/ulp/rtrs/rtrs-clt.h b/drivers/infiniband/ulp/rtrs/rtrs-clt.h
> index f848c0392d98..970b75633594 100644
> --- a/drivers/infiniband/ulp/rtrs/rtrs-clt.h
> +++ b/drivers/infiniband/ulp/rtrs/rtrs-clt.h
> @@ -75,6 +75,7 @@ struct rtrs_clt_con {
>  	unsigned int		cpu;
>  	struct mutex		con_mutex;
>  	int			cm_err;
> +	bool			has_dev;
>  };
>  
>  /**
> -- 
> 2.29.2
>