linux-kernel - Re: [PATCH 21/26] dax/region: Prevent range mapping allocation on sparse regions

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Date: Mon, 1 Apr 2024 10:07:48 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: Ira Weiny <ira.weiny@...el.com>, Fan Ni <fan.ni@...sung.com>,
 Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 Navneet Singh <navneet.singh@...el.com>
Cc: Dan Williams <dan.j.williams@...el.com>,
 Davidlohr Bueso <dave@...olabs.net>,
 Alison Schofield <alison.schofield@...el.com>,
 Vishal Verma <vishal.l.verma@...el.com>, linux-btrfs@...r.kernel.org,
 linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 21/26] dax/region: Prevent range mapping allocation on
 sparse regions



On 3/24/24 4:18 PM, Ira Weiny wrote:
> Sparse regions are not fully populated with memory and this complicates
> range mapping of dax devices on those regions.  There is no use case for
> range mapping on sparse regions.
> 
> Avoid the complication by prevent range mapping of dax devices on sparse
> regions.
> 
> Signed-off-by: Ira Weiny <ira.weiny@...el.com>
Reviewed-by: Dave Jiang <dave.jiang@...el.com>

> ---
>  drivers/dax/bus.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
> index bab19fc578d0..56dddaceeccb 100644
> --- a/drivers/dax/bus.c
> +++ b/drivers/dax/bus.c
> @@ -1452,6 +1452,8 @@ static umode_t dev_dax_visible(struct kobject *kobj, struct attribute *a, int n)
>  		return 0;
>  	if (a == &dev_attr_mapping.attr && is_static(dax_region))
>  		return 0;
> +	if (a == &dev_attr_mapping.attr && is_sparse(dax_region))
> +		return 0;
>  	if ((a == &dev_attr_align.attr ||
>  	     a == &dev_attr_size.attr) && is_static(dax_region))
>  		return 0444;
>