From: Hao Ge This is because OBJEXTS_ALLOC_FAIL and OBJEXTS_ALLOC_FAIL currently share the same bit position. Therefore, we cannot simply determine whether memcg_data still points to the slabobj_ext vector by checking folio->memcg_data & MEMCG_DATA_OBJEXTS. We can distinguish between these two cases by checking whether the upper bits set: 1) MEMCG_DATA_OBJEXTS is set, but upper bits are not set, so it should mean obj_exts allocation failed (OBJEXTS_ALLOC_FAIL), thus do not report error, or 2) MEMCG_DATA_OBJEXTS is set, and upper bits are also set, so someone did not clear a valid folio->memcg_data before freeing the folio (report error). So let's add check for memcg_data's upper bits in folio_memcg_kmem. Fixes: 7612833192d5 ("slab: Reuse first bit for OBJEXTS_ALLOC_FAIL") Signed-off-by: Hao Ge --- v2: Per Vlastimil and Harry's suggestion, instead of introducing a new bit, implement this by checking if the highest bit is set. Many thanks to Vlastimil and Harry. --- include/linux/memcontrol.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 873e510d6f8d..f9f7ba14be04 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -534,7 +534,9 @@ static inline struct mem_cgroup *get_mem_cgroup_from_objcg(struct obj_cgroup *ob static inline bool folio_memcg_kmem(struct folio *folio) { VM_BUG_ON_PGFLAGS(PageTail(&folio->page), &folio->page); - VM_BUG_ON_FOLIO(folio->memcg_data & MEMCG_DATA_OBJEXTS, folio); + VM_BUG_ON_FOLIO((folio->memcg_data & MEMCG_DATA_OBJEXTS) && + (folio->memcg_data & ~(ULONG_MAX >> 1)), + folio); return folio->memcg_data & MEMCG_DATA_KMEM; } -- 2.25.1