linux-kernel - Re: [RFC PATCH 07/14] nvme: Add RECOVERING nvme controller state

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Message-ID: <fc33dcfe-244c-412a-ab06-a554a66ada1b@grimberg.me>
Date: Sat, 27 Dec 2025 11:52:31 +0200
From: Sagi Grimberg <sagi@...mberg.me>
To: Mohamed Khalfella <mkhalfella@...estorage.com>
Cc: Chaitanya Kulkarni <kch@...dia.com>, Christoph Hellwig <hch@....de>,
 Jens Axboe <axboe@...nel.dk>, Keith Busch <kbusch@...nel.org>,
 Aaron Dailey <adailey@...estorage.com>,
 Randy Jennings <randyj@...estorage.com>, John Meneghini
 <jmeneghi@...hat.com>, Hannes Reinecke <hare@...e.de>,
 linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 07/14] nvme: Add RECOVERING nvme controller state



On 25/12/2025 19:17, Mohamed Khalfella wrote:
> On Thu 2025-12-25 15:29:52 +0200, Sagi Grimberg wrote:
>>
>> On 26/11/2025 4:11, Mohamed Khalfella wrote:
>>> Add NVME_CTRL_RECOVERING as a new controller state to be used when
>>> impacted controller is being recovered. A LIVE controller enters
>>> RECOVERING state when an IO error is encountered. While recovering
>>> inflight IOs will not be canceled if they timeout. These IOs will be
>>> canceled after recovery finishes. Also, while recovering a controller
>>> can not be reset or deleted. This is intentional because reset or delete
>>> will result in canceling inflight IOs. When recovery finishes, the
>>> impacted controller transitions from RECOVERING state to RESETTING state.
>>> Reset codepath takes care of queues teardown and inflight requests
>>> cancellation.
>> Is RECOVERING really capturing the nature of this state? Maybe RESETTLING?
>> or QUIESCING?
> Naming is hard. QUIESCING sounds better, I will renaming it to
> QUIESCING.
>
>>> Note, there is no transition from RECOVERING to RESETTING added to
>>> nvme_change_ctrl_state(). The reason is that user should not be allowed
>>> to reset or delete a controller that is being recovered.
>>>
>>> Add NVME_CTRL_RECOVERED controller flag. This flag is set on a controller
>>> about to schedule delayed work for time based recovery.
>>>
>>> Signed-off-by: Mohamed Khalfella <mkhalfella@...estorage.com>
>>> ---
>>>    drivers/nvme/host/core.c  | 10 ++++++++++
>>>    drivers/nvme/host/nvme.h  |  2 ++
>>>    drivers/nvme/host/sysfs.c |  1 +
>>>    3 files changed, 13 insertions(+)
>>>
>>> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
>>> index aa007a7b9606..f5b84bc327d3 100644
>>> --- a/drivers/nvme/host/core.c
>>> +++ b/drivers/nvme/host/core.c
>>> @@ -574,6 +574,15 @@ bool nvme_change_ctrl_state(struct nvme_ctrl *ctrl,
>>>    			break;
>>>    		}
>>>    		break;
>>> +	case NVME_CTRL_RECOVERING:
>>> +		switch (old_state) {
>>> +		case NVME_CTRL_LIVE:
>>> +			changed = true;
>>> +			fallthrough;
>>> +		default:
>>> +			break;
>>> +		}
>>> +		break;
>> That is a strange transition...
> Why is it strange?
>
> We transition to RECOVERING state only if controller is LIVE. This is
> when we expect to have inflight user IOs to be quiesced by CCR. We do
> not care about inflight requests in other states.

Sorry, got confused myself - I read it as the other way around...
I am missing RECOVERING -> RESETTING transition in this patch.