The patch titled
memcg: avoid use cmpxchg in swap cgroup maintainance
has been added to the -mm tree. Its filename is
memcg-avoid-use-cmpxchg-in-swap-cgroup-maintainance.patch
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------------------------------------------------------
Subject: memcg: avoid use cmpxchg in swap cgroup maintainance
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxx>
Reported-by: Sachin Sant <sachinp@xxxxxxxxxx> wrote:
Cc: Balbir Singh <balbir@xxxxxxxxxx>
Cc: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
Cc: Li Zefan <lizf@xxxxxxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_cgroup.c | 20 ++++++++++++++++----
1 file changed, 16 insertions(+), 4 deletions(-)
diff -puN mm/page_cgroup.c~memcg-avoid-use-cmpxchg-in-swap-cgroup-maintainance mm/page_cgroup.c
--- a/mm/page_cgroup.c~memcg-avoid-use-cmpxchg-in-swap-cgroup-maintainance
+++ a/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_e
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_en
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, unsigne
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;
_
Patches currently in -mm which might be from kamezawa.hiroyu@xxxxxxxxxxxxxx are
nommu-fix-build-breakage.patch
devmem-dont-allow-seek-to-last-page.patch
drivers-char-memc-cleanups.patch
cgroup-introduce-cancel_attach.patch
cgroup-introduce-coalesce-css_get-and-css_put.patch
cgroups-revamp-subsys-array.patch
cgroups-subsystem-module-loading-interface.patch
cgroups-subsystem-module-unloading.patch
cgroups-blkio-subsystem-as-module.patch
cgroups-clean-up-cgroup_pidlist_find-a-bit.patch
memcg-add-interface-to-move-charge-at-task-migration.patch
memcg-move-charges-of-anonymous-page.patch
memcg-improve-performance-in-moving-charge.patch
memcg-avoid-oom-during-moving-charge.patch
memcg-move-charges-of-anonymous-swap.patch
memcg-improve-performance-in-moving-swap-charge.patch
cgroup-implement-eventfd-based-generic-api-for-notifications.patch
memcg-extract-mem_group_usage-from-mem_cgroup_read.patch
memcg-rework-usage-of-stats-by-soft-limit.patch
memcg-implement-memory-thresholds.patch
memcg-typo-in-comment-to-mem_cgroup_print_oom_info.patch
memcg-use-generic-percpu-instead-of-private-implementation.patch
memcg-update-threshold-and-softlimit-at-commit-v2.patch
memcg-share-event-counter-rather-than-duplicate-v2.patch
memcg-update-memcg_testtxt.patch
memcg-handle-panic_on_oom=always-case-v2.patch
cgroups-fix-race-between-userspace-and-kernelspace.patch
cgroups-add-simple-listener-of-cgroup-events-to-documentation.patch
memcg-update-memcg_testtxt-to-describe-memory-thresholds.patch
memcg-fix-oom-kill-behavior-v3.patch
memcg-update-maintainer-list.patch
memcg-avoid-use-cmpxchg-in-swap-cgroup-maintainance.patch
linux-next.patch
memory-hotplug-allow-setting-of-phys_device.patch
memory-hotplug-s390-set-phys_device.patch
cgroups-net_cls-as-module.patch
vfs-introduce-fmode_neg_offset-for-allowing-negative-f_pos.patch
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