From 9f457179244a1c0316546b1760f8993d0d718861 Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Thu, 13 Aug 2020 10:40:54 -0400 Subject: mm: memcontrol: fix warning when allocating the root cgroup Commit 3e38e0aaca9e ("mm: memcg: charge memcg percpu memory to the parent cgroup") adds memory tracking to the memcg kernel structures themselves to make cgroups liable for the memory they are consuming through the allocation of child groups (which can be significant). This code is a bit awkward as it's spread out through several functions: The outermost function does memalloc_use_memcg(parent) to set up current->active_memcg, which designates which cgroup to charge, and the inner functions pass GFP_ACCOUNT to request charging for specific allocations. To make sure this dependency is satisfied at all times - to make sure we don't randomly charge whoever is calling the functions - the inner functions warn on !current->active_memcg. However, this triggers a false warning when the root memcg itself is allocated. No parent exists in this case, and so current->active_memcg is rightfully NULL. It's a false positive, not indicative of a bug. Delete the warnings for now, we can revisit this later. Fixes: 3e38e0aaca9e ("mm: memcg: charge memcg percpu memory to the parent cgroup") Signed-off-by: Johannes Weiner Reported-by: Stephen Rothwell Acked-by: Roman Gushchin Cc: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memcontrol.c | 6 ------ 1 file changed, 6 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index d59fd9af6e6333..9d87082e64aa30 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5137,9 +5137,6 @@ static int alloc_mem_cgroup_per_node_info(struct mem_cgroup *memcg, int node) if (!pn) return 1; - /* We charge the parent cgroup, never the current task */ - WARN_ON_ONCE(!current->active_memcg); - pn->lruvec_stat_local = alloc_percpu_gfp(struct lruvec_stat, GFP_KERNEL_ACCOUNT); if (!pn->lruvec_stat_local) { @@ -5222,9 +5219,6 @@ static struct mem_cgroup *mem_cgroup_alloc(void) goto fail; } - /* We charge the parent cgroup, never the current task */ - WARN_ON_ONCE(!current->active_memcg); - memcg->vmstats_local = alloc_percpu_gfp(struct memcg_vmstats_percpu, GFP_KERNEL_ACCOUNT); if (!memcg->vmstats_local) -- cgit 1.2.3-korg