Commit 9f457179 authored by Johannes Weiner's avatar Johannes Weiner Committed by Linus Torvalds

mm: memcontrol: fix warning when allocating the root cgroup

Commit 3e38e0aa ("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: 3e38e0aa ("mm: memcg: charge memcg percpu memory to the parent cgroup")
Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Reported-by: default avatarStephen Rothwell <sfr@canb.auug.org.au>
Acked-by: default avatarRoman Gushchin <guro@fb.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent dc06fe51
...@@ -5137,9 +5137,6 @@ static int alloc_mem_cgroup_per_node_info(struct mem_cgroup *memcg, int node) ...@@ -5137,9 +5137,6 @@ static int alloc_mem_cgroup_per_node_info(struct mem_cgroup *memcg, int node)
if (!pn) if (!pn)
return 1; 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, pn->lruvec_stat_local = alloc_percpu_gfp(struct lruvec_stat,
GFP_KERNEL_ACCOUNT); GFP_KERNEL_ACCOUNT);
if (!pn->lruvec_stat_local) { if (!pn->lruvec_stat_local) {
...@@ -5222,9 +5219,6 @@ static struct mem_cgroup *mem_cgroup_alloc(void) ...@@ -5222,9 +5219,6 @@ static struct mem_cgroup *mem_cgroup_alloc(void)
goto fail; 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, memcg->vmstats_local = alloc_percpu_gfp(struct memcg_vmstats_percpu,
GFP_KERNEL_ACCOUNT); GFP_KERNEL_ACCOUNT);
if (!memcg->vmstats_local) if (!memcg->vmstats_local)
......
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