Re: [PATCH v4 1/3] fs: allow per-device dax status checking for filesystems

[Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>]

>  /**
> - * __bdev_dax_supported() - Check if the device supports dax for filesystem
> + * bdev_dax_supported() - Check if the device supports dax for filesystem
>   * @sb: The superblock of the device
> + * @bdev: block device to check
>   * @blocksize: The block size of the device
>   *
>   * This is a library function for filesystems to check if the block device
> @@ -82,9 +83,9 @@ EXPORT_SYMBOL_GPL(fs_dax_get_by_bdev);
>   *
>   * Return: negative errno if unsupported, 0 if supported.
>   */
> -int __bdev_dax_supported(struct super_block *sb, int blocksize)
> +int bdev_dax_supported(struct super_block *sb, struct block_device *bdev,
> +		       int blocksize)
>  {
> -	struct block_device *bdev = sb->s_bdev;
>  	struct dax_device *dax_dev;
>  	pgoff_t pgoff;
>  	int err, id;

This now only uses sb for sb->s_id.  It might be better to use bdevname
to print the device name and don't bother passing a sb at all.