Hi Keith
Thanks for your kindly and detailed response and patch.
On 01/19/2018 04:42 PM, Keith Busch wrote:
> On Fri, Jan 19, 2018 at 04:14:02PM +0800, jianchao.wang wrote:
>> On 01/19/2018 04:01 PM, Keith Busch wrote:
>>> The nvme_dev_disable routine makes forward progress without depending on
>>> timeout handling to complete expired commands. Once controller disabling
>>> completes, there can't possibly be any started requests that can expire.
>>> So we don't need nvme_timeout to do anything for requests above the
>>> boundary.
>>>
>> Yes, once controller disabling completes, any started requests will be
>> handled and cannot expire.
>> But before the _boundary_, there could be a nvme_timeout context runs with
>> nvme_dev_disable in parallel.
>> If a timeout path grabs a request, then nvme_dev_disable cannot get and
>> cancel it.
>> So even though the nvme_dev_disable completes, there still could be a
>> request in nvme_timeout context.
>>
>> The worst case is :
>> nvme_timeout nvme_reset_work
>> if (ctrl->state == RESETTING ) nvme_dev_disable
>> nvme_dev_disable initializing procedure
>>
>> the nvme_dev_disable run with reinit procedure in nvme_reset_work in
>> parallel.
>
> Okay, I see what you're saying. That's a pretty obscure case, as normally
> we enter nvme_reset_work with the queues already disabled, but there
> are a few cases where we need nvme_reset_work to handle that.
>
> But if we are in that case, I think we really just want to sync the
> queues. What do you think of this?
>
> ---
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index fde6fd2e7eef..516383193416 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -3520,6 +3520,17 @@ void nvme_stop_queues(struct nvme_ctrl *ctrl)
> }
> EXPORT_SYMBOL_GPL(nvme_stop_queues);
>
> +void nvme_sync_queues(struct nvme_ctrl *ctrl)
> +{
> + struct nvme_ns *ns;
> +
> + mutex_lock(&ctrl->namespaces_mutex);
> + list_for_each_entry(ns, &ctrl->namespaces, list)
> + blk_sync_queue(ns->queue);
> + mutex_unlock(&ctrl->namespaces_mutex);
> +}
> +EXPORT_SYMBOL_GPL(nvme_sync_queues);
> +
> void nvme_start_queues(struct nvme_ctrl *ctrl)
> {
> struct nvme_ns *ns;
> diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
> index 8e7fc1b041b7..45b1b8ceddb6 100644
> --- a/drivers/nvme/host/nvme.h
> +++ b/drivers/nvme/host/nvme.h
> @@ -374,6 +374,7 @@ void nvme_complete_async_event(struct nvme_ctrl *ctrl,
> __le16 status,
>
> void nvme_stop_queues(struct nvme_ctrl *ctrl);
> void nvme_start_queues(struct nvme_ctrl *ctrl);
> +void nvme_sync_queues(struct nvme_ctrl *ctrl)
> void nvme_kill_queues(struct nvme_ctrl *ctrl);
> void nvme_unfreeze(struct nvme_ctrl *ctrl);
> void nvme_wait_freeze(struct nvme_ctrl *ctrl);
> diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
> index a2ffb557b616..1fe00be22ad1 100644
> --- a/drivers/nvme/host/pci.c
> +++ b/drivers/nvme/host/pci.c
> @@ -2289,8 +2289,10 @@ static void nvme_reset_work(struct work_struct *work)
> * If we're called to reset a live controller first shut it down before
> * moving on.
> */
> - if (dev->ctrl.ctrl_config & NVME_CC_ENABLE)
> + if (dev->ctrl.ctrl_config & NVME_CC_ENABLE) {
> nvme_dev_disable(dev, false);
> + nvme_sync_queues(&dev->ctrl);
> + }
>
> result = nvme_pci_enable(dev);
> if (result)
> --
>
We should not use blk_sync_queue here, the requeue_work and run_work will be
canceled.
Just flush_work(&q->timeout_work) should be ok.
In addition, we could check NVME_CC_ENABLE in nvme_dev_disable to avoid
redundant invoking.
:)
Thanks
Jianchao
