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

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Message-ID: <20251231224507.GN3864520-mkhalfella@purestorage.com>
Date: Wed, 31 Dec 2025 14:45:07 -0800
From: Mohamed Khalfella <mkhalfella@...estorage.com>
To: Sagi Grimberg <sagi@...mberg.me>
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 Sat 2025-12-27 11:52:31 +0200, Sagi Grimberg wrote:
> 
> 
> 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.

This is in patch 8 ("nvme: Implement cross-controller reset recovery").
It was not added to nvme_change_ctrl_state() because we do not want the
controller to be reset while in RECOVERING state.