Re: [PATCH v4 2/9] dax: use READ_ONCE() in dax_holder()

[Gregory Price <gourry@gourry.net>]

On Thu, Oct 08, 2026 at 01:19:53PM +0200, Miklos Szeredi wrote:
> A future fuse patch will utilize dax_holder() in RCU context to make sure
> that the holder can't be freed by a racing fs_put_dax.
> 
> This patch just makes sure that dax_holder() works properly in such a
> context by adding READ_ONCE() (equivalent to rcu_dereference minus sanity
> checks).
> 
> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Reviewed-by: Gregory Price (Meta) <gourry@gourry.net>

> ---
>  drivers/dax/super.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/dax/super.c b/drivers/dax/super.c
> index 25836f389bde..76e8d3654629 100644
> --- a/drivers/dax/super.c
> +++ b/drivers/dax/super.c
> @@ -642,7 +642,7 @@ EXPORT_SYMBOL_GPL(put_dax);
>   */
>  void *dax_holder(struct dax_device *dax_dev)
>  {
> -	return dax_dev->holder_data;
> +	return READ_ONCE(dax_dev->holder_data);
>  }
>  EXPORT_SYMBOL_GPL(dax_holder);
>  
> -- 
> 2.54.0
>