The patch titled
memcg: get/put parents at create/free
has been removed from the -mm tree. Its filename was
memcg-get-put-parents-at-create-free.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: memcg: get/put parents at create/free
From: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
The lifetime of struct cgroup and struct mem_cgroup is different and
mem_cgroup has its own reference count for handling references from
swap_cgroup.
This causes strange problem that the parent mem_cgroup dies while child
mem_cgroup alive, and this problem causes a bug in case of
use_hierarchy==1 because res_counter_uncharge climbs up the tree.
This patch is for avoiding it by getting the parent at create, and putting
it at freeing.
Signed-off-by: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
Reviewed-by; KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxx>
Cc: Li Zefan <lizf@xxxxxxxxxxxxxx>
Cc: Paul Menage <menage@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 23 ++++++++++++++++++++++-
1 file changed, 22 insertions(+), 1 deletion(-)
diff -puN mm/memcontrol.c~memcg-get-put-parents-at-create-free mm/memcontrol.c
--- a/mm/memcontrol.c~memcg-get-put-parents-at-create-free
+++ a/mm/memcontrol.c
@@ -202,6 +202,7 @@ pcg_default_flags[NR_CHARGE_TYPE] = {
static void mem_cgroup_get(struct mem_cgroup *mem);
static void mem_cgroup_put(struct mem_cgroup *mem);
+static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem);
static void mem_cgroup_charge_statistics(struct mem_cgroup *mem,
struct page_cgroup *pc,
@@ -2193,10 +2194,23 @@ static void mem_cgroup_get(struct mem_cg
static void mem_cgroup_put(struct mem_cgroup *mem)
{
- if (atomic_dec_and_test(&mem->refcnt))
+ if (atomic_dec_and_test(&mem->refcnt)) {
+ struct mem_cgroup *parent = parent_mem_cgroup(mem);
__mem_cgroup_free(mem);
+ if (parent)
+ mem_cgroup_put(parent);
+ }
}
+/*
+ * Returns the parent mem_cgroup in memcgroup hierarchy with hierarchy enabled.
+ */
+static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem)
+{
+ if (!mem->res.parent)
+ return NULL;
+ return mem_cgroup_from_res_counter(mem->res.parent, res);
+}
#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
static void __init enable_swap_cgroup(void)
@@ -2235,6 +2249,13 @@ mem_cgroup_create(struct cgroup_subsys *
if (parent && parent->use_hierarchy) {
res_counter_init(&mem->res, &parent->res);
res_counter_init(&mem->memsw, &parent->memsw);
+ /*
+ * We increment refcnt of the parent to ensure that we can
+ * safely access it on res_counter_charge/uncharge.
+ * This refcnt will be decremented when freeing this
+ * mem_cgroup(see mem_cgroup_put).
+ */
+ mem_cgroup_get(parent);
} else {
res_counter_init(&mem->res, NULL);
res_counter_init(&mem->memsw, NULL);
_
Patches currently in -mm which might be from nishimura@xxxxxxxxxxxxxxxxx are
origin.patch
migration-migrate_vmas-should-check-vma.patch
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