Messages in this thread | | | Date | Thu, 24 Sep 2020 16:05:42 -0400 | From | Johannes Weiner <> | Subject | Re: [PATCH v1 3/4] mm: introduce page memcg flags |
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On Tue, Sep 22, 2020 at 01:36:59PM -0700, Roman Gushchin wrote: > @@ -422,7 +421,13 @@ static inline void clear_page_mem_cgroup(struct page *page) > */ > static inline struct obj_cgroup **page_obj_cgroups(struct page *page) > { > - return (struct obj_cgroup **)(page->memcg_data & ~0x1UL); > + unsigned long memcg_data = page->memcg_data; > + > + VM_BUG_ON_PAGE(memcg_data && !test_bit(PG_MEMCG_OBJ_CGROUPS, > + &memcg_data), page); > + __clear_bit(PG_MEMCG_OBJ_CGROUPS, &memcg_data); > + > + return (struct obj_cgroup **)memcg_data;
Slab allocations set up page->memcg_data locklessly, right? AFAICS, the page_objcg lookup functions all need READ_ONCE() loads.
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