linux-kernel - Re: [PATCH] device-dax: don't set kobj parent during cdev init

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Date:   Fri, 10 Feb 2017 12:22:48 -0700
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Dan Williams <dan.j.williams@...el.com>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Sajjan Vikas C <vikas.cha.sajjan@....com>,
        Arnd Bergmann <arnd@...db.de>, Jan Kara <jack@...e.cz>
Cc:     linux-kernel@...r.kernel.org, linux-nvdimm@...ts.01.org
Subject: Re: [PATCH] device-dax: don't set kobj parent during cdev init

Hey,

Also on the subject of very minor fixes: I noticed drivers/dax is not in
the maintainers file. I just assumed the nvdimm list should have been
included with those from get_maintainers.

Thanks,

Logan

On 10/02/17 12:19 PM, Logan Gunthorpe wrote:
> I copied this code and per feedback from Greg Kroah-Hartman [1] the
> cdev's kobject's parent should not be set to the related device.
> This should have minor consequences but isn't doing what anyone
> expects it to.
> 
> This patch then fixes device-dax so it doesn't make the same mistake.
> 
> [1] https://lkml.org/lkml/2017/2/10/370
> 
> Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
> ---
>  drivers/dax/dax.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/drivers/dax/dax.c b/drivers/dax/dax.c
> index ed758b7..24e53b7 100644
> --- a/drivers/dax/dax.c
> +++ b/drivers/dax/dax.c
> @@ -699,13 +699,9 @@ struct dax_dev *devm_create_dax_dev(struct dax_region *dax_region,
>  		goto err_inode;
>  	}
>  
> -	/* device_initialize() so cdev can reference kobj parent */
> -	device_initialize(dev);
> -
>  	cdev = &dax_dev->cdev;
>  	cdev_init(cdev, &dax_fops);
>  	cdev->owner = parent->driver->owner;
> -	cdev->kobj.parent = &dev->kobj;
>  	rc = cdev_add(&dax_dev->cdev, dev_t, 1);
>  	if (rc)
>  		goto err_cdev;
> @@ -722,7 +718,7 @@ struct dax_dev *devm_create_dax_dev(struct dax_region *dax_region,
>  	dev->groups = dax_attribute_groups;
>  	dev->release = dax_dev_release;
>  	dev_set_name(dev, "dax%d.%d", dax_region->id, dax_dev->id);
> -	rc = device_add(dev);
> +	rc = device_register(dev);
>  	if (rc) {
>  		put_device(dev);
>  		return ERR_PTR(rc);
>