The patch titled
Subject: mm: memcg/slab: fix memory leak at non-root kmem_cache destroy
has been added to the -mm tree. Its filename is
mm-memcg-slab-fix-memory-leak-at-non-root-kmem_cache-destroy.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-memcg-slab-fix-memory-leak-at-non-root-kmem_cache-destroy.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-memcg-slab-fix-memory-leak-at-non-root-kmem_cache-destroy.patch
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------------------------------------------------------
From: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Subject: mm: memcg/slab: fix memory leak at non-root kmem_cache destroy
If the kmem_cache refcount is greater than one, we should not mark the
root kmem_cache as dying. If we mark the root kmem_cache dying
incorrectly, the non-root kmem_cache can never be destroyed. It resulted
in memory leak when memcg was destroyed. We can use the following steps
to reproduce.
1) Use kmem_cache_create() to create a new kmem_cache named A.
2) Coincidentally, the kmem_cache A is an alias for kmem_cache B,
so the refcount of B is just increased.
3) Use kmem_cache_destroy() to destroy the kmem_cache A, just
decrease the B's refcount but mark the B as dying.
4) Create a new memory cgroup and alloc memory from the kmem_cache
B. It leads to create a non-root kmem_cache for allocating memory.
5) When destroy the memory cgroup created in the step 4), the
non-root kmem_cache can never be destroyed.
If we repeat steps 4) and 5), this will cause a lot of memory leak. So
only when refcount reach zero, we mark the root kmem_cache as dying.
Link: http://lkml.kernel.org/r/20200716165103.83462-1-songmuchun@xxxxxxxxxxxxx
Fixes: 92ee383f6daa ("mm: fix race between kmem_cache destroy, create and deactivate")
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
Acked-by: Roman Gushchin <guro@xxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/slab_common.c | 35 ++++++++++++++++++++++++++++-------
1 file changed, 28 insertions(+), 7 deletions(-)
--- a/mm/slab_common.c~mm-memcg-slab-fix-memory-leak-at-non-root-kmem_cache-destroy
+++ a/mm/slab_common.c
@@ -326,6 +326,14 @@ int slab_unmergeable(struct kmem_cache *
if (s->refcount < 0)
return 1;
+#ifdef CONFIG_MEMCG_KMEM
+ /*
+ * Skip the dying kmem_cache.
+ */
+ if (s->memcg_params.dying)
+ return 1;
+#endif
+
return 0;
}
@@ -886,12 +894,15 @@ static int shutdown_memcg_caches(struct
return 0;
}
-static void flush_memcg_workqueue(struct kmem_cache *s)
+static void memcg_set_kmem_cache_dying(struct kmem_cache *s)
{
spin_lock_irq(&memcg_kmem_wq_lock);
s->memcg_params.dying = true;
spin_unlock_irq(&memcg_kmem_wq_lock);
+}
+static void flush_memcg_workqueue(struct kmem_cache *s)
+{
/*
* SLAB and SLUB deactivate the kmem_caches through call_rcu. Make
* sure all registered rcu callbacks have been invoked.
@@ -923,10 +934,6 @@ static inline int shutdown_memcg_caches(
{
return 0;
}
-
-static inline void flush_memcg_workqueue(struct kmem_cache *s)
-{
-}
#endif /* CONFIG_MEMCG_KMEM */
void slab_kmem_cache_release(struct kmem_cache *s)
@@ -944,8 +951,6 @@ void kmem_cache_destroy(struct kmem_cach
if (unlikely(!s))
return;
- flush_memcg_workqueue(s);
-
get_online_cpus();
get_online_mems();
@@ -955,6 +960,22 @@ void kmem_cache_destroy(struct kmem_cach
if (s->refcount)
goto out_unlock;
+#ifdef CONFIG_MEMCG_KMEM
+ memcg_set_kmem_cache_dying(s);
+
+ mutex_unlock(&slab_mutex);
+
+ put_online_mems();
+ put_online_cpus();
+
+ flush_memcg_workqueue(s);
+
+ get_online_cpus();
+ get_online_mems();
+
+ mutex_lock(&slab_mutex);
+#endif
+
err = shutdown_memcg_caches(s);
if (!err)
err = shutdown_cache(s);
_
Patches currently in -mm which might be from songmuchun@xxxxxxxxxxxxx are
mm-memcg-slab-fix-memory-leak-at-non-root-kmem_cache-destroy.patch
mm-page_alloc-skip-setting-nodemask-when-we-are-in-interrupt.patch
