>>> On 08.08.11 at 22:45, Dan Magenheimer <dan.magenheimer@xxxxxxxxxx> wrote:
> From: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
> Subject: [PATCH V6 1/4] mm: frontswap: swap data structure changes
>
> This first patch of four in the frontswap series makes available core
> swap data structures (swap_lock, swap_list and swap_info) that are
> needed by frontswap.c but we don't need to expose them to the dozens
> of files that include swap.h so we create a new swapfile.h just to
> extern-ify these.
>
> Also add frontswap-related elements to swap_info_struct. Frontswap_map
> points to vzalloc'ed one-bit-per-swap-page metadata that indicates
> whether the swap page is in frontswap or in the device and frontswap_pages
> counts how many pages are in frontswap. We don't tie these to
> CONFIG_FRONTSWAP to avoid unnecessary clutter around various frontswap
> hooks.
>
> [v6: rebase to 3.0-rc1]
> [v5: no change from v4]
> [v4: rebase to 2.6.39]
> Signed-off-by: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
> Reviewed-by: Konrad Wilk <konrad.wilk@xxxxxxxxxx>
> Acked-by: Seth Jennings <sjenning@xxxxxxxxxxxxxxxxxx>
> Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
> Cc: Hugh Dickins <hughd@xxxxxxxxxx>
> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> Cc: Nitin Gupta <ngupta@xxxxxxxxxx>
> Cc: Matthew Wilcox <matthew@xxxxxx>
> Cc: Chris Mason <chris.mason@xxxxxxxxxx>
> Cc: Jan Beulich <JBeulich@xxxxxxxxxx>
> Cc: Rik Riel <riel@xxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>
> --- linux/include/linux/swapfile.h 1969-12-31 17:00:00.000000000 -0700
> +++ frontswap/include/linux/swapfile.h 2011-08-08 08:59:03.951694506 -0600
> @@ -0,0 +1,13 @@
> +#ifndef _LINUX_SWAPFILE_H
> +#define _LINUX_SWAPFILE_H
> +
> +/*
> + * these were static in swapfile.c but frontswap.c needs them and we don't
> + * want to expose them to the dozens of source files that include swap.h
> + */
> +extern spinlock_t swap_lock;
> +extern struct swap_list_t swap_list;
> +extern struct swap_info_struct *swap_info[];
> +extern int try_to_unuse(unsigned int, bool, unsigned long);
> +
> +#endif /* _LINUX_SWAPFILE_H */
> --- linux/include/linux/swap.h 2011-08-08 08:19:25.880690134 -0600
> +++ frontswap/include/linux/swap.h 2011-08-08 08:59:03.952691415 -0600
> @@ -194,6 +194,8 @@ struct swap_info_struct {
> struct block_device *bdev; /* swap device or bdev of swap file */
> struct file *swap_file; /* seldom referenced */
> unsigned int old_block_size; /* seldom referenced */
#ifdef CONFIG_FRONTSWAP
> + unsigned long *frontswap_map; /* frontswap in-use, one bit per page */
> + unsigned int frontswap_pages; /* frontswap pages in-use counter */
#endif
(to eliminate any overhead with that config option unset)
Jan
> };
>
> struct swap_list_t {
--
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