Messages in this thread | | | Date | Thu, 18 Jun 2020 18:08:37 -0700 | From | Roman Gushchin <> | Subject | Re: [PATCH v6 05/19] mm: memcontrol: decouple reference counting from page accounting |
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On Thu, Jun 18, 2020 at 07:55:35AM -0700, Shakeel Butt wrote: > Not sure if my email went through, so, re-sending. > > On Mon, Jun 8, 2020 at 4:07 PM Roman Gushchin <guro@fb.com> wrote: > > > > From: Johannes Weiner <hannes@cmpxchg.org> > > > [...] > > @@ -3003,13 +3004,16 @@ void __memcg_kmem_uncharge_page(struct page *page, int order) > > */ > > void mem_cgroup_split_huge_fixup(struct page *head) > > { > > + struct mem_cgroup *memcg = head->mem_cgroup; > > int i; > > > > if (mem_cgroup_disabled()) > > return; > > > > A memcg NULL check is needed here.
Hm, it seems like the only way how it can be NULL is if mem_cgroup_disabled() is true:
int mem_cgroup_charge(struct page *page, struct mm_struct *mm, gfp_t gfp_mask) { unsigned int nr_pages = hpage_nr_pages(page); struct mem_cgroup *memcg = NULL; int ret = 0;
if (mem_cgroup_disabled()) goto out;
<...>
if (!memcg) memcg = get_mem_cgroup_from_mm(mm);
ret = try_charge(memcg, gfp_mask, nr_pages); if (ret) goto out_put;
css_get(&memcg->css); commit_charge(page, memcg);
Did you hit this issue in reality? The only possible scenario I can imagine is if the page was allocated before enabling memory cgroups.
Are you about this case?
Otherwise we put root_mem_cgroup there.
Thanks!
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