linux-kernel - Re: [PATCH] nvme: unquiesce the queue before cleaup it

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Date:   Sun, 22 Apr 2018 22:25:40 +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

No, I only tested it on PCIe one.
And sorry for that I didn't state that.

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);
>>>  
>>
>> _______________________________________________
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> 
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