Re: [PATCH 05/11] mm: swap: Implement generic handler for swap_activate

[Andrew Morton <akpm@linux-foundation.org>]

On Mon, 16 Apr 2012 13:17:49 +0100
Mel Gorman <mgorman@suse.de> wrote:

> The version of swap_activate introduced is sufficient for swap-over-NFS
> but would not provide enough information to implement a generic handler.
> This patch shuffles things slightly to ensure the same information is
> available for aops->swap_activate() as is available to the core.
> 
> No functionality change.
> 
> ...
>
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -587,6 +587,8 @@ typedef struct {
>  typedef int (*read_actor_t)(read_descriptor_t *, struct page *,
>  		unsigned long, unsigned long);
>  
> +struct swap_info_struct;

Please put forward declarations at top-of-file.  To prevent accidental
duplication later on.

>  struct address_space_operations {
>  	int (*writepage)(struct page *page, struct writeback_control *wbc);
>  	int (*readpage)(struct file *, struct page *);
>
> ...
>
> --- a/mm/page_io.c
> +++ b/mm/page_io.c

Have you tested all this code with CONFIG_SWAP=n?

Have you sought to minimise additional new code when CONFIG_SWAP=n?