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authorKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>2009-06-17 02:32:53 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-17 06:47:42 +0400
commit355cfa73ddff2fb8fa14e93bd94a057cc022512e (patch)
tree7ff70cd56d533070d50b06db6ba0086e8aab0d71 /include/linux/swap.h
parentcb4b86ba47bb0937b71fb825b3ed88adf7a190f0 (diff)
downloadlinux-355cfa73ddff2fb8fa14e93bd94a057cc022512e.tar.xz
mm: modify swap_map and add SWAP_HAS_CACHE flag
This is a part of the patches for fixing memcg's swap accountinf leak. But, IMHO, not a bad patch even if no memcg. There are 2 kinds of references to swap. - reference from swap entry - reference from swap cache Then, - If there is swap cache && swap's refcnt is 1, there is only swap cache. (*) swapcount(entry) == 1 && find_get_page(swapper_space, entry) != NULL This counting logic have worked well for a long time. But considering that we cannot know there is a _real_ reference or not by swap_map[], current usage of counter is not very good. This patch adds a flag SWAP_HAS_CACHE and recored information that a swap entry has a cache or not. This will remove -1 magic used in swapfile.c and be a help to avoid unnecessary find_get_page(). Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Tested-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Cc: Balbir Singh <balbir@in.ibm.com> Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Dhaval Giani <dhaval@linux.vnet.ibm.com> Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/swap.h')
-rw-r--r--include/linux/swap.h14
1 files changed, 9 insertions, 5 deletions
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 259e96c150ef..fed5e8e1104b 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -129,9 +129,10 @@ enum {
#define SWAP_CLUSTER_MAX 32
-#define SWAP_MAP_MAX 0x7fff
-#define SWAP_MAP_BAD 0x8000
-
+#define SWAP_MAP_MAX 0x7ffe
+#define SWAP_MAP_BAD 0x7fff
+#define SWAP_HAS_CACHE 0x8000 /* There is a swap cache of entry. */
+#define SWAP_COUNT_MASK (~SWAP_HAS_CACHE)
/*
* The in-memory structure used to track swap areas.
*/
@@ -281,7 +282,7 @@ extern long total_swap_pages;
extern void si_swapinfo(struct sysinfo *);
extern swp_entry_t get_swap_page(void);
extern swp_entry_t get_swap_page_of_type(int);
-extern int swap_duplicate(swp_entry_t);
+extern void swap_duplicate(swp_entry_t);
extern int swapcache_prepare(swp_entry_t);
extern int valid_swaphandles(swp_entry_t, unsigned long *);
extern void swap_free(swp_entry_t);
@@ -353,9 +354,12 @@ static inline void show_swap_cache_info(void)
}
#define free_swap_and_cache(swp) is_migration_entry(swp)
-#define swap_duplicate(swp) is_migration_entry(swp)
#define swapcache_prepare(swp) is_migration_entry(swp)
+static inline void swap_duplicate(swp_entry_t swp)
+{
+}
+
static inline void swap_free(swp_entry_t swp)
{
}