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authorKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>2009-06-16 15:32:53 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-16 19:47:42 -0700
commit355cfa73ddff2fb8fa14e93bd94a057cc022512e (patch)
tree7ff70cd56d533070d50b06db6ba0086e8aab0d71 /mm/swap_state.c
parentcb4b86ba47bb0937b71fb825b3ed88adf7a190f0 (diff)
downloadvexpress-lsk-355cfa73ddff2fb8fa14e93bd94a057cc022512e.tar.gz
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 'mm/swap_state.c')
-rw-r--r--mm/swap_state.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 19bdf3017a9..b9ca029673a 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -292,7 +292,10 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
/*
* Swap entry may have been freed since our caller observed it.
*/
- if (!swapcache_prepare(entry))
+ err = swapcache_prepare(entry);
+ if (err == -EEXIST) /* seems racy */
+ continue;
+ if (err) /* swp entry is obsolete ? */
break;
/*