Re: [PATCH v8 4/8] btrfs: use the page-cache for super block reading

[David Sterba <dsterba@xxxxxxx>]

On Fri, Feb 14, 2020 at 12:24:32AM +0900, Johannes Thumshirn wrote:
> -	bh = __bread(bdev, bytenr / BTRFS_BDEV_BLOCKSIZE, BTRFS_SUPER_INFO_SIZE);
> -	/*
> -	 * If we fail to read from the underlying devices, as of now
> -	 * the best option we have is to mark it EIO.
> -	 */
> -	if (!bh)
> -		return -EIO;
> +	page = read_cache_page_gfp(mapping, bytenr >> PAGE_SHIFT, GFP_NOFS);
> +	if (IS_ERR(page))
> +		return ERR_PTR(-ENOMEM);

This should be 'return page', read_cache_page_gfp can return more
errors than just ENOMEM.