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authorVladimir Davydov <vdavydov@parallels.com>2014-04-07 15:39:28 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-04-07 16:36:13 -0700
commitb8529907ba35d625fa4b85d3e4dc8021be97c1f3 (patch)
tree88ba9609669e3f82b475f7a8bcaa927d5e5928b5 /mm/memcontrol.c
parent051dd46050f2a9bdfff8cc067f8987069eae1743 (diff)
memcg, slab: do not destroy children caches if parent has aliases
Currently we destroy children caches at the very beginning of kmem_cache_destroy(). This is wrong, because the root cache will not necessarily be destroyed in the end - if it has aliases (refcount > 0), kmem_cache_destroy() will simply decrement its refcount and return. In this case, at best we will get a bunch of warnings in dmesg, like this one: kmem_cache_destroy kmalloc-32:0: Slab cache still has objects CPU: 1 PID: 7139 Comm: modprobe Tainted: G B W 3.13.0+ #117 Call Trace: dump_stack+0x49/0x5b kmem_cache_destroy+0xdf/0xf0 kmem_cache_destroy_memcg_children+0x97/0xc0 kmem_cache_destroy+0xf/0xf0 xfs_mru_cache_uninit+0x21/0x30 [xfs] exit_xfs_fs+0x2e/0xc44 [xfs] SyS_delete_module+0x198/0x1f0 system_call_fastpath+0x16/0x1b At worst - if kmem_cache_destroy() will race with an allocation from a memcg cache - the kernel will panic. This patch fixes this by moving children caches destruction after the check if the cache has aliases. Plus, it forbids destroying a root cache if it still has children caches, because each children cache keeps a reference to its parent. Signed-off-by: Vladimir Davydov <vdavydov@parallels.com> Cc: Michal Hocko <mhocko@suse.cz> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: David Rientjes <rientjes@google.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: Glauber Costa <glommer@gmail.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.c13
1 files changed, 6 insertions, 7 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c22d8bf42d9a..29501f040568 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3321,15 +3321,10 @@ void mem_cgroup_destroy_cache(struct kmem_cache *cachep)
schedule_work(&cachep->memcg_params->destroy);
}
-void kmem_cache_destroy_memcg_children(struct kmem_cache *s)
+int __kmem_cache_destroy_memcg_children(struct kmem_cache *s)
{
struct kmem_cache *c;
- int i;
-
- if (!s->memcg_params)
- return;
- if (!s->memcg_params->is_root_cache)
- return;
+ int i, failed = 0;
/*
* If the cache is being destroyed, we trust that there is no one else
@@ -3363,8 +3358,12 @@ void kmem_cache_destroy_memcg_children(struct kmem_cache *s)
c->memcg_params->dead = false;
cancel_work_sync(&c->memcg_params->destroy);
kmem_cache_destroy(c);
+
+ if (cache_from_memcg_idx(s, i))
+ failed++;
}
mutex_unlock(&activate_kmem_mutex);
+ return failed;
}
static void mem_cgroup_destroy_all_caches(struct mem_cgroup *memcg)