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authorKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>2010-03-15 00:34:57 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2010-03-17 18:43:47 -0700
commite9e58a4ec3b1086d1ed8c915311aef1ae55454fd (patch)
treea500ec01cce13fa17f2400ac57f4ad36f4d37bca /mm
parenta3d3203e4bb40f253b1541e310dc0f9305be7c84 (diff)
downloadconfigs-e9e58a4ec3b1086d1ed8c915311aef1ae55454fd.tar.gz
memcg: avoid use cmpxchg in swap cgroup maintainance
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>
Diffstat (limited to 'mm')
-rw-r--r--mm/page_cgroup.c20
1 files changed, 16 insertions, 4 deletions
diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
index 3dd88539a0e..6c0081441a3 100644
--- a/mm/page_cgroup.c
+++ b/mm/page_cgroup.c
@@ -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;