Date:   Mon, 13 Feb 2023 17:14:22 -0700
From:   Nathan Chancellor <nathan@kernel.org>
To:     Longlong Xia <xialonglong1@huawei.com>
Cc:     gregkh@linuxfoundation.org, chenwandun@huawei.com,
        linux-kernel@vger.kernel.org, rafael@kernel.org,
        sunnanyong@huawei.com, wangkefeng.wang@huawei.com,
        linux-btrfs@vger.kernel.org
Subject: Re: [PATCH -next v2 1/3] driver core: add error handling for
 devtmpfs_create_node()
Message-ID: <Y+rSXg14z1Myd8Px@dev-arch.thelio-3990X>
References: <20230210095444.4067307-1-xialonglong1@huawei.com>
 <20230210095444.4067307-2-xialonglong1@huawei.com>
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In-Reply-To: <20230210095444.4067307-2-xialonglong1@huawei.com>
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Hi Longlong,

On Fri, Feb 10, 2023 at 09:54:42AM +0000, Longlong Xia wrote:
> In some cases, devtmpfs_create_node() can return error value.
> So, make use of it.
> 
> Signed-off-by: Longlong Xia <xialonglong1@huawei.com>
> ---
>  drivers/base/core.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 7dab705f2937..aaa3088e5456 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -3405,7 +3405,9 @@ int device_add(struct device *dev)
>  		if (error)
>  			goto SysEntryError;
>  
> -		devtmpfs_create_node(dev);
> +		error = devtmpfs_create_node(dev);
> +		if (error)
> +			goto DevtmpfsError;
>  	}
>  
>  	/* Notify clients of device addition.  This call must come
> @@ -3461,6 +3463,8 @@ int device_add(struct device *dev)
>  done:
>  	put_device(dev);
>  	return error;
> + DevtmpfsError:
> +	device_remove_sys_dev_entry(dev);
>   SysEntryError:
>  	if (MAJOR(dev->devt))
>  		device_remove_file(dev, &dev_attr_dev);
> -- 
> 2.25.1
> 

After this change in -next as commit 31b4b6730fd4 ("driver core: add
error handling for devtmpfs_create_node()"), my test machines failed to
boot after the rootfs could not be mounted. I added some logging to see
which device was failing, which triggers a few times with the exact same
message:

  device: 'btrfs-control': devtmpfs_create_node() failed, err = -17

with -17 being -EEXIST. I am not sure why this device is getting
registered more than once, it appears to occur during module insertion
though, as I am able to get to systemd starting within the initrd.

Should this particular return value be downgraded to a warning so that
the device still loads or should the driver be fixed? I have cc'd the
btrfs mailing list, in case they have any input.

Cheers,
Nathan