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SubjectRe: [PATCH V2 1/4] Frontswap (was Transcendent Memory): swap data structure changes
On Fri, 28 May 2010 10:40:41 -0700
Dan Magenheimer <dan.magenheimer@oracle.com> wrote:

> [PATCH V2 1/4] Frontswap (was Transcendent Memory): swap data structure changes
>
> Core swap data structures are needed by frontswap.c but we don't
> need to expose them to the dozens of files that include swap.h
> so create a new swapfile.h just to extern-ify these.
>
> Add frontswap-related elements to swap_info_struct. Don't tie
> these to CONFIG_FRONTSWAP to avoid unnecessary clutter around
> various frontswap hooks.
>
> Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
>
> Diffstat:
> swap.h | 2 ++
> swapfile.h | 13 +++++++++++++
> 2 files changed, 15 insertions(+)
>
> --- linux-2.6.34/include/linux/swapfile.h 1969-12-31 17:00:00.000000000 -0700
> +++ linux-2.6.34-frontswap/include/linux/swapfile.h 2010-05-21 16:36:45.000000000 -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-2.6.34/include/linux/swap.h 2010-05-16 15:17:36.000000000 -0600
> +++ linux-2.6.34-frontswap/include/linux/swap.h 2010-05-24 10:13:41.000000000 -0600
> @@ -182,6 +182,8 @@ 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 */
> + unsigned long *frontswap_map; /* frontswap in-use, one bit per page */
> + unsigned int frontswap_pages; /* frontswap pages in-use counter */

Is a 32-bit uint large enough? Maybe there are other things in swap
which restrict us to less than 16TB, dunno.


> };
>
> struct swap_list_t {


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