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Subject: Re: [PATCH RESEND v6 2/9] dax: Introduce holder for dax_device
To:     Shiyang Ruan <ruansy.fnst@fujitsu.com>,
        linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org,
        nvdimm@lists.linux.dev, linux-mm@kvack.org,
        linux-fsdevel@vger.kernel.org, dm-devel@redhat.com
Cc:     djwong@kernel.org, dan.j.williams@intel.com, david@fromorbit.com,
        hch@lst.de, agk@redhat.com, snitzer@redhat.com
References: <20210730100158.3117319-1-ruansy.fnst@fujitsu.com>
 <20210730100158.3117319-3-ruansy.fnst@fujitsu.com>
From:   Jane Chu <jane.chu@oracle.com>
Organization: Oracle Corporation
Message-ID: <e844fc54-113f-239d-da23-fa140aeea9d7@oracle.com>
Date:   Thu, 5 Aug 2021 18:02:34 -0700
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On 7/30/2021 3:01 AM, Shiyang Ruan wrote:
> --- a/drivers/dax/super.c
> +++ b/drivers/dax/super.c
> @@ -214,6 +214,8 @@ enum dax_device_flags {
>    * @cdev: optional character interface for "device dax"
>    * @host: optional name for lookups where the device path is not available
>    * @private: dax driver private data
> + * @holder_rwsem: prevent unregistration while holder_ops is in progress
> + * @holder_data: holder of a dax_device: could be filesystem or mapped device
>    * @flags: state and boolean properties

Perhaps add two documentary lines for @ops and @holder_ops?
>    */
>   struct dax_device {
> @@ -222,8 +224,11 @@ struct dax_device {
>   	struct cdev cdev;
>   	const char *host;
>   	void *private;
> +	struct rw_semaphore holder_rwsem;
> +	void *holder_data;
>   	unsigned long flags;
>   	const struct dax_operations *ops;
> +	const struct dax_holder_operations *holder_ops;
>   };

thanks,
-jane