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-rw-r--r--mm/memcontrol.c28
1 files changed, 28 insertions, 0 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2b7cd24d4cda..06a595fd6400 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3637,6 +3637,34 @@ __memcg_kmem_newpage_charge(gfp_t gfp, struct mem_cgroup **_memcg, int order)
int ret;
*_memcg = NULL;
+
+ /*
+ * Disabling accounting is only relevant for some specific memcg
+ * internal allocations. Therefore we would initially not have such
+ * check here, since direct calls to the page allocator that are marked
+ * with GFP_KMEMCG only happen outside memcg core. We are mostly
+ * concerned with cache allocations, and by having this test at
+ * memcg_kmem_get_cache, we are already able to relay the allocation to
+ * the root cache and bypass the memcg cache altogether.
+ *
+ * There is one exception, though: the SLUB allocator does not create
+ * large order caches, but rather service large kmallocs directly from
+ * the page allocator. Therefore, the following sequence when backed by
+ * the SLUB allocator:
+ *
+ * memcg_stop_kmem_account();
+ * kmalloc(<large_number>)
+ * memcg_resume_kmem_account();
+ *
+ * would effectively ignore the fact that we should skip accounting,
+ * since it will drive us directly to this function without passing
+ * through the cache selector memcg_kmem_get_cache. Such large
+ * allocations are extremely rare but can happen, for instance, for the
+ * cache arrays. We bring this test here.
+ */
+ if (!current->mm || current->memcg_kmem_skip_account)
+ return true;
+
memcg = try_get_mem_cgroup_from_mm(current->mm);
/*