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| author | KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> | 2009-06-16 22:32:53 (GMT) |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-06-17 02:47:42 (GMT) |
| commit | 355cfa73ddff2fb8fa14e93bd94a057cc022512e (patch) | |
| tree | 7ff70cd56d533070d50b06db6ba0086e8aab0d71 /mm/swap_state.c | |
| parent | cb4b86ba47bb0937b71fb825b3ed88adf7a190f0 (diff) | |
| download | linux-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 'mm/swap_state.c')
| -rw-r--r-- | mm/swap_state.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/mm/swap_state.c b/mm/swap_state.c index 19bdf30..b9ca029 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+ err = swapcache_prepare(entry); + if (err == -EEXIST) /* seems racy */ + continue; + if (err) /* swp entry is obsolete ?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; /* |