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Date:   Fri, 10 Jun 2022 01:13:46 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Sun Feng <loyou85@gmail.com>
Cc:     axboe@kernel.dk, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] block: fix attribute_group lost if set before add_disk
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References: <1654845389-21741-1-git-send-email-loyou85@gmail.com>
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On Fri, Jun 10, 2022 at 03:16:29PM +0800, Sun Feng wrote:
> after commit 52b85909f85d("block: fold register_disk into device_add_disk")
> when set attribute_group with following code:
> 
>   disk_to_dev(disk)->groups = attr_groups;
>   err = add_disk(disk);
> 
> disk_to_dev(disk)->groups will set to NULL in device_add_disk,
> 
>   static inline int __must_check add_disk(struct gendisk *disk)
>   {
>        	return device_add_disk(NULL, disk, NULL);
>   }
>   int __must_check device_add_disk(struct device *parent, ...
>                                  const struct attribute_group **groups)
>   {
> 	…
> 	ddev->groups = groups
> 
> and it will lose attribute group set.

Well, your are not supposed to set the attribute group yourself, but
instead pass it to device_add_disk.