Re: [PATCH V3 5/9] dax/fsdev: use __va(phys) for kaddr in direct_access

[Dave Jiang <dave.jiang@intel.com>]

On 5/30/26 9:51 AM, John Groves wrote:
> From: John Groves <John@Groves.net>
> 
> Use __va(phys) instead of virt_addr + linear_offset for the kaddr
> return in __fsdev_dax_direct_access(). The previous code added a
> device-linear byte offset to virt_addr (which is __va of ranges[0]),
> but for multi-range devices with physical gaps between ranges, this
> linear arithmetic crosses the gap and produces a wrong kernel virtual
> address. Using __va(phys) where phys comes from dax_pgoff_to_phys()
> is correct for any range layout because the direct map translates
> each physical address independently.
> 
> Fixes: 759455848df0b ("dax: Save the kva from memremap")
> Signed-off-by: John Groves <john@groves.net>

Reviewed-by: Dave Jiang <dave.jiang@intel.com>

one comment below

> ---
>  drivers/dax/fsdev.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/dax/fsdev.c b/drivers/dax/fsdev.c
> index 42aac7e952516..a2d2eb20fb4d0 100644
> --- a/drivers/dax/fsdev.c
> +++ b/drivers/dax/fsdev.c
> @@ -51,9 +51,7 @@ static long __fsdev_dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
>  	struct dev_dax *dev_dax = dax_get_private(dax_dev);
>  	size_t size = nr_pages << PAGE_SHIFT;
>  	size_t offset = pgoff << PAGE_SHIFT;
> -	void *virt_addr = dev_dax->virt_addr + offset;

With this change, there's no more dev_dax->virt_addr usage? Should that be removed?

DJ

>  	phys_addr_t phys;
> -	unsigned long local_pfn;
>  
>  	phys = dax_pgoff_to_phys(dev_dax, pgoff, size);
>  	if (phys == -1) {
> @@ -63,11 +61,10 @@ static long __fsdev_dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
>  	}
>  
>  	if (kaddr)
> -		*kaddr = virt_addr;
> +		*kaddr = __va(phys);
>  
> -	local_pfn = PHYS_PFN(phys);
>  	if (pfn)
> -		*pfn = local_pfn;
> +		*pfn = PHYS_PFN(phys);
>  
>  	/*
>  	 * Use cached_size which was computed at probe time. The size cannot