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memcg: avoid use cmpxchg in swap cgroup maintainance

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swap_cgroup uses 2bytes data and uses cmpxchg in a new operation.  2byte
cmpxchg/xchg is not available on some archs.  This patch replaces
cmpxchg/xchg with operations under lock.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reported-by: Sachin Sant <sachinp@in.ibm.com> wrote:
Acked-by: Balbir Singh <balbir@in.ibm.com>
Acked-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
KAMEZAWA Hiroyuki 2010-03-15 00:34:57 -04:00 committed by Linus Torvalds
parent a3d3203e4b
commit e9e58a4ec3
1 changed files with 16 additions and 4 deletions
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20
mm/page_cgroup.c
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@ -284,6 +284,7 @@ static DEFINE_MUTEX(swap_cgroup_mutex);
struct swap_cgroup_ctrl {
struct page **map;
unsigned long length;
spinlock_t lock;
};
struct swap_cgroup_ctrl swap_cgroup_ctrl[MAX_SWAPFILES];
@ -353,16 +354,22 @@ unsigned short swap_cgroup_cmpxchg(swp_entry_t ent,
struct swap_cgroup_ctrl *ctrl;
struct page *mappage;
struct swap_cgroup *sc;
unsigned long flags;
unsigned short retval;
ctrl = &swap_cgroup_ctrl[type];
mappage = ctrl->map[idx];
sc = page_address(mappage);
sc += pos;
if (cmpxchg(&sc->id, old, new) == old)
return old;
spin_lock_irqsave(&ctrl->lock, flags);
retval = sc->id;
if (retval == old)
sc->id = new;
else
return 0;
retval = 0;
spin_unlock_irqrestore(&ctrl->lock, flags);
return retval;
}
/**
@ -383,13 +390,17 @@ unsigned short swap_cgroup_record(swp_entry_t ent, unsigned short id)
struct page *mappage;
struct swap_cgroup *sc;
unsigned short old;
unsigned long flags;
ctrl = &swap_cgroup_ctrl[type];
mappage = ctrl->map[idx];
sc = page_address(mappage);
sc += pos;
old = xchg(&sc->id, id);
spin_lock_irqsave(&ctrl->lock, flags);
old = sc->id;
sc->id = id;
spin_unlock_irqrestore(&ctrl->lock, flags);
return old;
}
@ -441,6 +452,7 @@ int swap_cgroup_swapon(int type, unsigned long max_pages)
mutex_lock(&swap_cgroup_mutex);
ctrl->length = length;
ctrl->map = array;
spin_lock_init(&ctrl->lock);
if (swap_cgroup_prepare(type)) {
/* memory shortage */
ctrl->map = NULL;