Re: [PATCH] nvme-tcp: Use __dev_get_by_name instead dev_get_by_name for OPT_HOST_IFACE

From: Prabhakar Kushwaha <prabhakar.pkin@gmail.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Prabhakar Kushwaha <pkushwaha@marvell.com>,
	linux-nvme@lists.infradead.org, Sagi Grimberg <sagi@grimberg.me>,
	kbusch@kernel.org, axboe@fb.com,  martin.belanger@dell.com,
	aelior@marvell.com,  Omkar Kulkarni <okulkarni@marvell.com>,
	Shai Malin <smalin@marvell.com>,
	malin1024@gmail.com
Subject: Re: [PATCH] nvme-tcp: Use __dev_get_by_name instead dev_get_by_name for OPT_HOST_IFACE
Date: Sun, 11 Jul 2021 18:47:37 +0530	[thread overview]
Message-ID: <CAJ2QiJJ8cUL2fOfuYeLqa=LOvCBRgZ3wJ=-t4t7CL-xOpS2dtw@mail.gmail.com> (raw)
In-Reply-To: <20210624063551.GB26612@lst.de>

Hi Christoph,

On Thu, Jun 24, 2021 at 12:05 PM Christoph Hellwig <hch@lst.de> wrote:
>
> I've applied the slightly updated version below to make it a little
> more clear what is going on:
>
> ---
> From 9de7d173c10b6be09fe9d5b7010ef182465897a1 Mon Sep 17 00:00:00 2001
> From: Prabhakar Kushwaha <pkushwaha@marvell.com>
> Date: Fri, 18 Jun 2021 16:39:56 +0300
> Subject: nvme-tcp: use __dev_get_by_name instead dev_get_by_name for
>  OPT_HOST_IFACE
>
> dev_get_by_name() finds network device by name but it also increases the
> reference count.
>
> If a nvme-tcp queue is present and the network device driver is removed
> before nvme_tcp, we will face the following continuous log:
>
>   "kernel:unregister_netdevice: waiting for <eth> to become free. Usage count = 2"
>
> And rmmod further halts. Similar case arises during reboot/shutdown
> with nvme-tcp queue present and both never completes.
>
> To fix this, use __dev_get_by_name() which finds network device by
> name without increasing any reference counter.
>
> Fixes: 3ede8f72a9a2 ("nvme-tcp: allow selecting the network interface for connections")
> Signed-off-by: Omkar Kulkarni <okulkarni@marvell.com>
> Signed-off-by: Shai Malin <smalin@marvell.com>
> Signed-off-by: Prabhakar Kushwaha <pkushwaha@marvell.com>
> Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
> [hch: remove the ->ndev member entirely]
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---

I am not finding this patch on updated "branch nvme-5.14" having the
latest commit 0755d3be2d9b("nvme-tcp: can't set sk_user_data without
write_lock").
Am I missing something?  Please note, earlier it was there with commit
ff5af4bfb6af.

Issue can still be found on the nvme-5.14 branch (top of the tree).
Are you planning to fix this problem using any other approach?

--pk

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