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Date:   Fri, 27 Apr 2018 16:51:02 +0800
From:   "jianchao.wang" <jianchao.w.wang@...cle.com>
To:     Max Gurtovoy <maxg@...lanox.com>, keith.busch@...el.com,
        axboe@...com, hch@....de, sagi@...mberg.me,
        linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nvme: unquiesce the queue before cleaup it

Hi Max

On 04/26/2018 06:23 PM, Max Gurtovoy wrote:
> Hi Jianchao,
> I actually tried this scenario with real HW and was able to repro the hang.
> Unfortunatly, after applying your patch I got NULL deref:
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000014
> WARNING: CPU: 5 PID: 0 at block/blk-mq.c:526 __blk_mq_complete_request+0x154/0x160
> 

Could you please share the whole backtrace here ?

Thanks
Jianchao

> I guess it's the same issue the IsraelR/Bart/Ming are trying to fix in the block layer regarding completing requests.
> I'll add IsraelR proposed fix to nvme-rdma that is currently on hold and see what happens.
> Nontheless, I don't like the situation that the reset and delete flows can run concurrently.
> 
> -Max.
> 
> On 4/26/2018 11:27 AM, jianchao.wang wrote:
>> Hi Max
>>
>> I did a similar test on nvme-rdma, the underlying fabric is soft-RoCE.
>> A io loop, reset controller loop  and a delete/create controller loop.
>> And found io hang below:
>>
>> [  230.884590] WARNING: CPU: 0 PID: 150 at /home/will/u04/source_code/linux-stable/drivers/nvme/host/rdma.c:1755 nvme_rdma_reset_ctrl_work+0x3d/0xb0 [nvme_rdma]
>> [  230.884689] CPU: 0 PID: 150 Comm: kworker/u16:3 Not tainted 4.17.0-rc1+ #16
>> [  230.884690] Hardware name: LENOVO 10MLS0E339/3106, BIOS M1AKT22A 06/27/2017
>> [  230.884693] Workqueue: nvme-reset-wq nvme_rdma_reset_ctrl_work [nvme_rdma]
>> [  230.884696] RIP: 0010:nvme_rdma_reset_ctrl_work+0x3d/0xb0 [nvme_rdma]
>> [  230.884697] RSP: 0018:ffffa9e30255be40 EFLAGS: 00010246
>> [  230.884699] RAX: 0000000000000000 RBX: ffff9633b64c2000 RCX: 0000000000000000
>> [  230.884700] RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffffffff9ac05516
>> [  230.884701] RBP: ffff9633b64c23b8 R08: 0000000000000001 R09: 0000000000000000
>> [  230.884702] R10: 0000000000000000 R11: 0000000000000000 R12: ffff9633b64c2970
>> [  230.884703] R13: 0000000000000000 R14: 0ffff96340ffcc80 R15: ffff9634102af9c0
>> [  230.884705] FS:  0000000000000000(0000) GS:ffff963422c00000(0000) knlGS:0000000000000000
>> [  230.884706] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [  230.884707] CR2: 0000000001ce9ca4 CR3: 000000038040f005 CR4: 00000000003606f0
>> [  230.884708] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> [  230.884709] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>> [  230.884710] Call Trace:
>> [  230.884717]  process_one_work+0x1c0/0x680
>> [  230.884722]  worker_thread+0x22b/0x430
>> [  230.884728]  kthread+0x100/0x140
>> [  230.884730]  ? rescuer_thread+0x370/0x370
>> [  230.884731]  ? kthread_delayed_work_timer_fn+0x80/0x80
>> [  230.884736]  ret_from_fork+0x24/0x30
>> [  230.884744] Code: ff 48 8d ab b8 03 00 00 48 89 ef e8 1e 25 d7 d9 31 f6 48 89 df e8 44 f9 ff ff be 04 00 00 00 48 89 ef e8 b7 13 d7 d9 84 c0 75 07 <0f> 0b 5b 5d 41 5c c3 31 f6 48 89 df e8 b2 fa ff ff 85 c0 75 39
>> [  230.884799] irq event stamp: 88150
>> [  230.884802] hardirqs last  enabled at (88149): [<ffffffff9ac05529>] _raw_spin_unlock_irqrestore+0x59/0x70
>> [  230.884803] hardirqs last disabled at (88150): [<ffffffff9ae0116c>] error_entry+0x6c/0xc0
>> [  230.884805] softirqs last  enabled at (87998): [<ffffffff9aa603a0>] sk_common_release+0x60/0xd0
>> [  230.884807] softirqs last disabled at (87996): [<ffffffff9aa60375>] sk_common_release+0x35/0xd0
>> [  230.884808] ---[ end trace c03fac253b80d77d ]---
>> [  277.472094] INFO: task kworker/u16:0:6 blocked for more than 30 seconds.
>> [  277.473482]       Tainted: G        W         4.17.0-rc1+ #16
>> [  277.474825] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>> [  277.476293] kworker/u16:0   D    0     6      2 0x80000000
>> [  277.476317] Workqueue: nvme-delete-wq nvme_delete_ctrl_work
>> [  277.476335] Call Trace:
>> [  277.476365]  ? __schedule+0x3de/0xac0
>> [  277.476393]  schedule+0x3c/0x90
>> [  277.476405]  blk_mq_freeze_queue_wait+0x44/0x90
>> [  277.476419]  ? wait_woken+0x90/0x90
>> [  277.476437]  blk_cleanup_queue+0xe1/0x280
>> [  277.476453]  nvme_ns_remove+0x1c8/0x260
>> [  277.476475]  nvme_remove_namespaces+0x7f/0xa0
>> [  277.476495]  nvme_delete_ctrl_work+0x4b/0x80
>> [  277.476508]  process_one_work+0x1c0/0x680
>> [  277.476535]  worker_thread+0x22b/0x430
>> [  277.476562]  kthread+0x100/0x140
>> [  277.476572]  ? rescuer_thread+0x370/0x370
>> [  277.476579]  ? kthread_delayed_work_timer_fn+0x80/0x80
>> [  277.476598]  ret_from_fork+0x24/0x30
>>
>> 00000000ea33345b {.op=READ, .cmd_flags=23, .rq_flags=MQ_INFLIGHT|IO_STAT, .state=idle, .tag=19, .internal_tag=-1}
>> 0000000071218c5a {.op=READ, .cmd_flags=23, .rq_flags=MQ_INFLIGHT|IO_STAT, .state=idle, .tag=45, .internal_tag=-1}
>> root@...l-ThinkCentre-M910s:/sys/kernel/debug/block/nvme1c1n1# cat state
>> DYING|BYPASS|NOMERGES|SAME_COMP|NONROT|IO_STAT|DISCARD|NOXMERGES|INIT_DONE|NO_SG_MERGE|POLL|WC|FUA|STATS|QUIESCED
>>
>> This is due to a race following:
>>
>> nvme_delete_ctrl                    nvme_rdma_reset_ctrl_work
>>    -> change state to DELETING
>>    -> queue delete_work
>>                                        -> nvme_rdma_shutdown_ctrl
>>                                          -> nvme_stop_queues
>>                                            -> blk_mq_quiesce_queue
>>                                                         -> change to LIVE state fails
>>                                          -> return
>> nvme_delete_ctrl_work
>>    -> nvme_remove_namespaces
>>      -> nvme_ns_remove
>>        -> blk_cleanup_queue
>>          -> blk_freeze_queue
>>
>> This patch could also fix this issue.
>>
>> Thanks
>> Jianchao
>>
>> On 04/22/2018 11:00 PM, jianchao.wang wrote:
>>> Hi Max
>>>
>>> That's really appreciated!
>>> Here is my test script.
>>>
>>> loop_reset_controller.sh
>>> #!/bin/bash
>>> while true
>>> do
>>>     echo 1 > /sys/block/nvme0n1/device/reset_controller
>>>     sleep 1
>>> done
>>>
>>> loop_unbind_driver.sh
>>> #!/bin/bash
>>> while true
>>> do
>>>     echo "0000:02:00.0" > /sys/bus/pci/drivers/nvme/unbind
>>>     sleep 2
>>>     echo "0000:02:00.0" > /sys/bus/pci/drivers/nvme/bind
>>>     sleep 2
>>> done
>>>
>>> loop_io.sh
>>> #!/bin/bash
>>>
>>> file="/dev/nvme0n1"
>>> echo $file
>>> while true;
>>> do
>>>     if [ -e $file ];then
>>>         fio fio_job_rand_read.ini
>>>     else
>>>         echo "Not found"
>>>         sleep 1
>>>     fi
>>> done
>>>
>>> The fio jobs is as below:
>>> size=512m
>>> rw=randread
>>> bs=4k
>>> ioengine=libaio
>>> iodepth=64
>>> direct=1
>>> numjobs=16
>>> filename=/dev/nvme0n1
>>> group_reporting
>>>
>>> I started in sequence, loop_io.sh, loop_reset_controller.sh, loop_unbind_driver.sh.
>>> And if lucky, I will get io hang in 3 minutes. ;)
>>> Such as:
>>>
>>> [  142.858074] nvme nvme0: pci function 0000:02:00.0
>>> [  144.972256] nvme nvme0: failed to mark controller state 1
>>> [  144.972289] nvme nvme0: Removing after probe failure status: 0
>>> [  185.312344] INFO: task bash:1673 blocked for more than 30 seconds.
>>> [  185.312889]       Not tainted 4.17.0-rc1+ #6
>>> [  185.312950] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>>> [  185.313049] bash            D    0  1673   1629 0x00000080
>>> [  185.313061] Call Trace:
>>> [  185.313083]  ? __schedule+0x3de/0xac0
>>> [  185.313103]  schedule+0x3c/0x90
>>> [  185.313111]  blk_mq_freeze_queue_wait+0x44/0x90
>>> [  185.313123]  ? wait_woken+0x90/0x90
>>> [  185.313133]  blk_cleanup_queue+0xe1/0x280
>>> [  185.313145]  nvme_ns_remove+0x1c8/0x260
>>> [  185.313159]  nvme_remove_namespaces+0x7f/0xa0
>>> [  185.313170]  nvme_remove+0x6c/0x130
>>> [  185.313181]  pci_device_remove+0x36/0xb0
>>> [  185.313193]  device_release_driver_internal+0x160/0x230
>>> [  185.313205]  unbind_store+0xfe/0x150
>>> [  185.313219]  kernfs_fop_write+0x114/0x190
>>> [  185.313234]  __vfs_write+0x23/0x150
>>> [  185.313246]  ? rcu_read_lock_sched_held+0x3f/0x70
>>> [  185.313252]  ? preempt_count_sub+0x92/0xd0
>>> [  185.313259]  ? __sb_start_write+0xf8/0x200
>>> [  185.313271]  vfs_write+0xc5/0x1c0
>>> [  185.313284]  ksys_write+0x45/0xa0
>>> [  185.313298]  do_syscall_64+0x5a/0x1a0
>>> [  185.313308]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
>>>
>>> And get following information in block debugfs:
>>> root@...l-ThinkCentre-M910s:/sys/kernel/debug/block/nvme0n1# cat hctx6/cpu6/rq_list
>>> 000000001192d19b {.op=READ, .cmd_flags=, .rq_flags=IO_STAT, .state=idle, .tag=69, .internal_tag=-1}
>>> 00000000c33c8a5b {.op=READ, .cmd_flags=, .rq_flags=IO_STAT, .state=idle, .tag=78, .internal_tag=-1}
>>> root@...l-ThinkCentre-M910s:/sys/kernel/debug/block/nvme0n1# cat state
>>> DYING|BYPASS|NOMERGES|SAME_COMP|NONROT|IO_STAT|DISCARD|NOXMERGES|INIT_DONE|NO_SG_MERGE|POLL|WC|FUA|STATS|QUIESCED
>>>
>>> We can see there were reqs on ctx rq_list and the request_queue is QUIESCED.
>>>
>>> Thanks again !!
>>> Jianchao
>>>
>>> On 04/22/2018 10:48 PM, Max Gurtovoy wrote:
>>>>
>>>>
>>>> On 4/22/2018 5:25 PM, jianchao.wang wrote:
>>>>> Hi Max
>>>>>
>>>>> No, I only tested it on PCIe one.
>>>>> And sorry for that I didn't state that.
>>>>
>>>> Please send your exact test steps and we'll run it using RDMA transport.
>>>> I also want to run a mini regression on this one since it may effect other flows.
>>>>
>>>>>
>>>>> Thanks
>>>>> Jianchao
>>>>>
>>>>> On 04/22/2018 10:18 PM, Max Gurtovoy wrote:
>>>>>> Hi Jianchao,
>>>>>> Since this patch is in the core, have you tested it using some fabrics drives too ? RDMA/FC ?
>>>>>>
>>>>>> thanks,
>>>>>> Max.
>>>>>>
>>>>>> On 4/22/2018 4:32 PM, jianchao.wang wrote:
>>>>>>> Hi keith
>>>>>>>
>>>>>>> Would you please take a look at this patch.
>>>>>>>
>>>>>>> This issue could be reproduced easily with a driver bind/unbind loop,
>>>>>>> a reset loop and a IO loop at the same time.
>>>>>>>
>>>>>>> Thanks
>>>>>>> Jianchao
>>>>>>>
>>>>>>> On 04/19/2018 04:29 PM, Jianchao Wang wrote:
>>>>>>>> There is race between nvme_remove and nvme_reset_work that can
>>>>>>>> lead to io hang.
>>>>>>>>
>>>>>>>> nvme_remove                    nvme_reset_work
>>>>>>>> -> change state to DELETING
>>>>>>>>                                   -> fail to change state to LIVE
>>>>>>>>                                   -> nvme_remove_dead_ctrl
>>>>>>>>                                     -> nvme_dev_disable
>>>>>>>>                                       -> quiesce request_queue
>>>>>>>>                                     -> queue remove_work
>>>>>>>> -> cancel_work_sync reset_work
>>>>>>>> -> nvme_remove_namespaces
>>>>>>>>      -> splice ctrl->namespaces
>>>>>>>>                                   nvme_remove_dead_ctrl_work
>>>>>>>>                                   -> nvme_kill_queues
>>>>>>>>      -> nvme_ns_remove               do nothing
>>>>>>>>        -> blk_cleanup_queue
>>>>>>>>          -> blk_freeze_queue
>>>>>>>> Finally, the request_queue is quiesced state when wait freeze,
>>>>>>>> we will get io hang here.
>>>>>>>>
>>>>>>>> To fix it, unquiesce the request_queue directly before nvme_ns_remove.
>>>>>>>> We have spliced the ctrl->namespaces, so nobody could access them
>>>>>>>> and quiesce the queue any more.
>>>>>>>>
>>>>>>>> Signed-off-by: Jianchao Wang <jianchao.w.wang@...cle.com>
>>>>>>>> ---
>>>>>>>>     drivers/nvme/host/core.c | 9 ++++++++-
>>>>>>>>     1 file changed, 8 insertions(+), 1 deletion(-)
>>>>>>>>
>>>>>>>> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
>>>>>>>> index 9df4f71..0e95082 100644
>>>>>>>> --- a/drivers/nvme/host/core.c
>>>>>>>> +++ b/drivers/nvme/host/core.c
>>>>>>>> @@ -3249,8 +3249,15 @@ void nvme_remove_namespaces(struct nvme_ctrl *ctrl)
>>>>>>>>         list_splice_init(&ctrl->namespaces, &ns_list);
>>>>>>>>         up_write(&ctrl->namespaces_rwsem);
>>>>>>>>     -    list_for_each_entry_safe(ns, next, &ns_list, list)
>>>>>>>> +    /*
>>>>>>>> +     * After splice the namespaces list from the ctrl->namespaces,
>>>>>>>> +     * nobody could get them anymore, let's unquiesce the request_queue
>>>>>>>> +     * forcibly to avoid io hang.
>>>>>>>> +     */
>>>>>>>> +    list_for_each_entry_safe(ns, next, &ns_list, list) {
>>>>>>>> +        blk_mq_unquiesce_queue(ns->queue);
>>>>>>>>             nvme_ns_remove(ns);
>>>>>>>> +    }
>>>>>>>>     }
>>>>>>>>     EXPORT_SYMBOL_GPL(nvme_remove_namespaces);
>>>>>>>>    
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> Linux-nvme mailing list
>>>>>>> Linux-nvme@...ts.infradead.org
>>>>>>> https://urldefense.proofpoint.com/v2/url?u=http-3A__lists.infradead.org_mailman_listinfo_linux-2Dnvme&d=DwICAg&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=7WdAxUBeiTUTCy8v-7zXyr4qk7sx26ATvfo6QSTvZyQ&m=eQ9q70WFDS-d0s-KndBw8MOJvcBM6wuuKUNklqTC3h8&s=oBasfz9JoJw4yQF4EaWcNfKChZ1HMCkfHVZqyjvYVHQ&e=
>>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> Linux-nvme mailing list
>>>>>> Linux-nvme@...ts.infradead.org
>>>>>> https://urldefense.proofpoint.com/v2/url?u=http-3A__lists.infradead.org_mailman_listinfo_linux-2Dnvme&d=DwICAg&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=7WdAxUBeiTUTCy8v-7zXyr4qk7sx26ATvfo6QSTvZyQ&m=eQ9q70WFDS-d0s-KndBw8MOJvcBM6wuuKUNklqTC3h8&s=oBasfz9JoJw4yQF4EaWcNfKChZ1HMCkfHVZqyjvYVHQ&e=
>>>>>>
>>>
>>> _______________________________________________
>>> Linux-nvme mailing list
>>> Linux-nvme@...ts.infradead.org
>>> https://urldefense.proofpoint.com/v2/url?u=http-3A__lists.infradead.org_mailman_listinfo_linux-2Dnvme&d=DwIGaQ&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=7WdAxUBeiTUTCy8v-7zXyr4qk7sx26ATvfo6QSTvZyQ&m=ivKrSi6co_9l91-czj52P2ABAPyKOwv9GrD3UeCbhio&s=2U00IBVk4CVt0Q-jiZX3sEWEEA2IleOjPU_PD38Fgvg&e=
>>>
> 

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