Re: [PATCH] netfs: Miscellaneous fixes

[Matthew Wilcox]

On Mon, Apr 26, 2021 at 10:06:24PM +0100, David Howells wrote:
> @@ -968,7 +968,7 @@ int netfs_readpage(struct file *file,
>  		return -ENOMEM;
>  	}
>  	rreq->mapping	= page_file_mapping(page);
> -	rreq->start	= page_index(page) * PAGE_SIZE;
> +	rreq->start	= page_offset(page);

This one needs to use page_file_offset() because swap-over-NFS.

> @@ -1105,8 +1105,8 @@ int netfs_write_begin(struct file *file, struct address_space *mapping,
>  	rreq = netfs_alloc_read_request(ops, netfs_priv, file);
>  	if (!rreq)
>  		goto error;
> -	rreq->mapping		= page->mapping;
> -	rreq->start		= page->index * PAGE_SIZE;
> +	rreq->mapping		= page_file_mapping(page);

There's nothing wrong with using page->mapping here.  The swap-over-NFS
path doesn't use write_begin, it uses O_DIRECT writes.