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Subject: Re: [PATCH 2/2] scsi: libsas: delete sas port if expander discover
 failed
To:     Jason Yan <yanaijie@huawei.com>, <martin.petersen@oracle.com>,
        <jejb@linux.vnet.ibm.com>
References: <20190514024239.47313-1-yanaijie@huawei.com>
 <20190514024239.47313-2-yanaijie@huawei.com>
CC:     <linux-scsi@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <hare@suse.com>, <dan.j.williams@intel.com>, <jthumshirn@suse.de>,
        <hch@lst.de>, <huangdaode@hisilicon.com>,
        <chenxiang66@hisilicon.com>, <miaoxie@huawei.com>,
        <zhaohongjiang@huawei.com>, Linuxarm <linuxarm@huawei.com>
From:   John Garry <john.garry@huawei.com>
Message-ID: <6b831fd1-825e-19a7-0981-bc182cf4685f@huawei.com>
Date:   Tue, 14 May 2019 11:45:23 +0100
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On 14/05/2019 03:42, Jason Yan wrote:
> The sas_port(phy->port) allocated in sas_ex_discover_expander() will not
> be deleted when the expander failed to discover. This will cause
> resource leak and a further issue of kernel BUG like below:
>
> [159785.843156]  port-2:17:29: trying to add phy phy-2:17:29 fails: it's
> already part of another port
> [159785.852144] ------------[ cut here  ]------------
> [159785.856833] kernel BUG at drivers/scsi/scsi_transport_sas.c:1086!
> [159785.863000] Internal error: Oops - BUG: 0 [#1] SMP
> [159785.867866] CPU: 39 PID: 16993 Comm: kworker/u96:2 Tainted: G
> W  OE     4.19.25-vhulk1901.1.0.h111.aarch64 #1
> [159785.878458] Hardware name: Huawei Technologies Co., Ltd.
> Hi1620EVBCS/Hi1620EVBCS, BIOS Hi1620 CS B070 1P TA 03/21/2019
> [159785.889231] Workqueue: 0000:74:02.0_disco_q sas_discover_domain
> [159785.895224] pstate: 40c00009 (nZcv daif +PAN +UAO)
> [159785.900094] pc : sas_port_add_phy+0x188/0x1b8
> [159785.904524] lr : sas_port_add_phy+0x188/0x1b8
> [159785.908952] sp : ffff0001120e3b80
> [159785.912341] x29: ffff0001120e3b80 x28: 0000000000000000
> [159785.917727] x27: ffff802ade8f5400 x26: ffff0000681b7560
> [159785.923111] x25: ffff802adf11a800 x24: ffff0000680e8000
> [159785.928496] x23: ffff802ade8f5728 x22: ffff802ade8f5708
> [159785.933880] x21: ffff802adea2db40 x20: ffff802ade8f5400
> [159785.939264] x19: ffff802adea2d800 x18: 0000000000000010
> [159785.944649] x17: 00000000821bf734 x16: ffff00006714faa0
> [159785.950033] x15: ffff0000e8ab4ecf x14: 7261702079646165
> [159785.955417] x13: 726c612073277469 x12: ffff00006887b830
> [159785.960802] x11: ffff00006773eaa0 x10: 7968702079687020
> [159785.966186] x9 : 0000000000002453 x8 : 726f702072656874
> [159785.971570] x7 : 6f6e6120666f2074 x6 : ffff802bcfb21290
> [159785.976955] x5 : ffff802bcfb21290 x4 : 0000000000000000
> [159785.982339] x3 : ffff802bcfb298c8 x2 : 337752b234c2ab00
> [159785.987723] x1 : 337752b234c2ab00 x0 : 0000000000000000
> [159785.993108] Process kworker/u96:2 (pid: 16993, stack limit =
> 0x0000000072dae094)
> [159786.000576] Call trace:
> [159786.003097]  sas_port_add_phy+0x188/0x1b8
> [159786.007179]  sas_ex_get_linkrate.isra.5+0x134/0x140
> [159786.012130]  sas_ex_discover_expander+0x128/0x408
> [159786.016906]  sas_ex_discover_dev+0x218/0x4c8
> [159786.021249]  sas_ex_discover_devices+0x9c/0x1a8
> [159786.025852]  sas_discover_root_expander+0x134/0x160
> [159786.030802]  sas_discover_domain+0x1b8/0x1e8
> [159786.035148]  process_one_work+0x1b4/0x3f8
> [159786.039230]  worker_thread+0x54/0x470
> [159786.042967]  kthread+0x134/0x138
> [159786.046269]  ret_from_fork+0x10/0x18
> [159786.049918] Code: 91322300 f0004402 91178042 97fe4c9b (d4210000)
> [159786.056083] Modules linked in: hns3_enet_ut(OE) hclge(OE) hnae3(OE)
> hisi_sas_test_hw(OE) hisi_sas_test_main(OE) serdes(OE)
> [159786.067202] ---[ end trace 03622b9e2d99e196  ]---
> [159786.071893] Kernel panic - not syncing: Fatal exception
> [159786.077190] SMP: stopping secondary CPUs
> [159786.081192] Kernel Offset: disabled
> [159786.084753] CPU features: 0x2,a2a00a38
>
> Fixes: 2908d778ab3e ("[SCSI] aic94xx: new driver")
> Reported-by: Jian Luo <luojian5@huawei.com>
> Signed-off-by: Jason Yan <yanaijie@huawei.com>
> CC: John Garry <john.garry@huawei.com>
> ---
>  drivers/scsi/libsas/sas_expander.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c
> index 83f2fd70ce76..9f7e2457360e 100644
> --- a/drivers/scsi/libsas/sas_expander.c
> +++ b/drivers/scsi/libsas/sas_expander.c
> @@ -1019,6 +1019,8 @@ static struct domain_device *sas_ex_discover_expander(
>  		list_del(&child->dev_list_node);
>  		spin_unlock_irq(&parent->port->dev_list_lock);
>  		sas_put_device(child);
> +		sas_port_delete(phy->port);
> +		phy->port = NULL;

This looks ok.

However, I wonder if we miss something else, and I see this code earlier 
in sas_ex_discover_expander():

     kref_get(&parent->kref);
     child->parent = parent;
     child->port = port;
     child->iproto = phy->attached_iproto;
     child->tproto = phy->attached_tproto;

I assume the kref get is for the child referencing the parent. Do we 
need the kref put? I couldn't see it.

If yes, maybe it should it go in sas_free_device(), along with kfree() 
for expander device phys.

Thanks,
John

>  		return NULL;
>  	}
>  	list_add_tail(&child->siblings, &parent->ex_dev.children);
>