6.6-stable review patch. If anyone has any objections, please let me know.
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From: Shakeel Butt shakeel.butt@linux.dev
[ Upstream commit 9f01b4954490d4ccdbcc2b9be34a9921ceee9cbb ]
Currently on cpu hotplug teardown, only memcg stock is drained but we need to drain the obj stock as well otherwise we will miss the stats accumulated on the target cpu as well as the nr_bytes cached. The stats include MEMCG_KMEM, NR_SLAB_RECLAIMABLE_B & NR_SLAB_UNRECLAIMABLE_B. In addition we are leaking reference to struct obj_cgroup object.
Link: https://lkml.kernel.org/r/20250310230934.2913113-1-shakeel.butt@linux.dev Fixes: bf4f059954dc ("mm: memcg/slab: obj_cgroup API") Signed-off-by: Shakeel Butt shakeel.butt@linux.dev Reviewed-by: Roman Gushchin roman.gushchin@linux.dev Acked-by: Johannes Weiner hannes@cmpxchg.org Cc: Michal Hocko mhocko@kernel.org Cc: Muchun Song muchun.song@linux.dev Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- mm/memcontrol.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 9bf5a69e20d87..ab9afcd372a93 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2378,9 +2378,18 @@ static void drain_all_stock(struct mem_cgroup *root_memcg) static int memcg_hotplug_cpu_dead(unsigned int cpu) { struct memcg_stock_pcp *stock; + struct obj_cgroup *old; + unsigned long flags;
stock = &per_cpu(memcg_stock, cpu); + + /* drain_obj_stock requires stock_lock */ + local_lock_irqsave(&memcg_stock.stock_lock, flags); + old = drain_obj_stock(stock); + local_unlock_irqrestore(&memcg_stock.stock_lock, flags); + drain_stock(stock); + obj_cgroup_put(old);
return 0; }