linux-kernel - Re: [PATCH RFC 3/3] nvme: delay failover by command quiesce timeout

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Message-ID: <97fd8c08-e5bb-4b4b-9ec0-0eea9af1da1d@flourine.local>
Date: Tue, 15 Apr 2025 14:05:23 +0200
From: Daniel Wagner <dwagner@...e.de>
To: Nilay Shroff <nilay@...ux.ibm.com>
Cc: Daniel Wagner <wagi@...nel.org>, Christoph Hellwig <hch@....de>, 
	Sagi Grimberg <sagi@...mberg.me>, Keith Busch <kbusch@...nel.org>, Hannes Reinecke <hare@...e.de>, 
	John Meneghini <jmeneghi@...hat.com>, randyj@...estorage.com, 
	Mohamed Khalfella <mkhalfella@...estorage.com>, linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 3/3] nvme: delay failover by command quiesce timeout

On Tue, Apr 01, 2025 at 07:02:11PM +0530, Nilay Shroff wrote:
 > -	kblockd_schedule_work(&ns->head->requeue_work);
> > +	spin_lock_irqsave(&ctrl->lock, flags);
> > +	list_add_tail(&req->queuelist, &ctrl->failover_list);
> > +	spin_unlock_irqrestore(&ctrl->lock, flags);
> > +
> 
> Why do we need to wait until error_recovery for scheduling failover?

This is where the delay is added to the processing. The failed requests
(timeout) are held back by the delay here and after the wait the are
immediately fall over

> Can't we schedule failover as soon as we get path error? Also can't
> we avoid failover_list? 

Then we have exactly what we have now. An failed request is rescheduled
to the next path immediately.