diff options
| author | Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> | 2009-01-29 14:25:11 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-01-29 18:04:43 -0800 |
| commit | 7bcc1bb1232de6efc0b85e0c7fe38e90b2436318 (patch) | |
| tree | 3952a706885f4c57217f4196f055a7c16d0af80b /mm/memcontrol.c | |
| parent | baef99a08a2e23d9386b47e53fa5f0d44fc98f66 (diff) | |
| download | linux-7bcc1bb1232de6efc0b85e0c7fe38e90b2436318.tar.bz2 | |
memcg: get/put parents at create/free
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@mxp.nes.nec.co.jp>
Reviewed-by; KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/memcontrol.c')
| -rw-r--r-- | mm/memcontrol.c | 23 |
1 files changed, 22 insertions, 1 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 4d0ea3ceba6d..76feccd26dc3 100644 --- a/mm/memcontrol.c +++ b/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_cgroup *mem) 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 *ss, struct cgroup *cont) 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); |