linux-kernel - Re: [PATCH] nvme-pci: Make sure to ring doorbell when last request is short-circuited

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Date:   Tue, 20 Sep 2022 09:06:06 -0700
From:   Mohamed Khalfella <mkhalfella@...estorage.com>
To:     Keith Busch <kbusch@...nel.org>
Cc:     stable@...r.kernel.org, Eric Badger <ebadger@...estorage.com>,
        Jens Axboe <axboe@...com>, Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        Tao Chiu <taochiu@...ology.com>,
        Leon Chien <leonchien@...ology.com>,
        Cody Wong <codywong@...ology.com>,
        "open list:NVM EXPRESS DRIVER" <linux-nvme@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] nvme-pci: Make sure to ring doorbell when last request
 is short-circuited

On 2022-09-19 11:35:09 -0600, Keith Busch wrote:
> > Fixes: d4060d2be1132 ("nvme-pci: fix controller reset hang when racing with nvme_timeout")
> 
> I revisted that commit, and it doesn't sound correct. Specifically this part:
> 
>     5) reset_work() continues to setup_io_queues() as it observes no error
>        in init_identify(). However, the admin queue has already been
>        quiesced in dev_disable(). Thus, any following commands would be
>        blocked forever in blk_execute_rq().
> 
> When a timeout occurs in the CONNECTING state, the timeout handler unquiesces
> the queue specifically to flush out any blocked requests. Is that commit really
> necessary? I'd rather just revert it to save the extra per-IO checks if not.

I can not speak with certainty whether 4060d2be1132 need to be reverted or not.
I will need to carefully inspect reset code path and do more experiments. If this
commit gets reverted we still need to add `nvme_commit_rqs` to `nvme_mq_admin_ops`.