mm: reuse_swap_page replaces can_share_swap_page

A good place to free up old swap is where do_wp_page(), or do_swap_page(),
is about to redirty the page: the data on disk is then stale and won't be
read again; and if we do decide to write the page out later, using the
previous swap location makes an unnecessary disk seek very likely.

So give can_share_swap_page() the side-effect of delete_from_swap_cache()
when it safely can.  And can_share_swap_page() was always a misleading
name, the more so if it has a side-effect: rename it reuse_swap_page().

Irrelevant cleanup nearby: remove swap_token_default_timeout definition
from swap.h: it's used nowhere.

Signed-off-by: Hugh Dickins <[email protected]>
Cc: Lee Schermerhorn <[email protected]>
Acked-by: Rik van Riel <[email protected]>
Cc: Nick Piggin <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: Robin Holt <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Hugh Dickins 2009-01-06 14:39:34 -08:00 • committed by Linus Torvalds
commit 7b1fe59793
3 changed files with 15 additions and 10 deletions

View file

@ -304,7 +304,7 @@ extern unsigned int count_swap_pages(int, int);
extern sector_t map_swap_page(struct swap_info_struct *, pgoff_t);
extern sector_t swapdev_block(int, pgoff_t);
extern struct swap_info_struct *get_swap_info_struct(unsigned);
extern int can_share_swap_page(struct page *);
extern int reuse_swap_page(struct page *);
extern int remove_exclusive_swap_page(struct page *);
extern int remove_exclusive_swap_page_ref(struct page *);
struct backing_dev_info;
@ -372,8 +372,6 @@ static inline struct page *lookup_swap_cache(swp_entry_t swp)
return NULL;
}
#define can_share_swap_page(p) (page_mapcount(p) == 1)
static inline int add_to_swap_cache(struct page *page, swp_entry_t entry,
gfp_t gfp_mask)
{
@ -388,7 +386,7 @@ static inline void delete_from_swap_cache(struct page *page)
{
}
#define swap_token_default_timeout 0
#define reuse_swap_page(page) (page_mapcount(page) == 1)
static inline int remove_exclusive_swap_page(struct page *p)
{