From dccd5ee2625d50239510bcd73ed78559005e00a3 Mon Sep 17 00:00:00 2001 From: Hao Li Date: Thu, 26 Feb 2026 19:51:37 +0800 Subject: [PATCH] memcg: fix slab accounting in refill_obj_stock() trylock path In the trylock path of refill_obj_stock(), mod_objcg_mlstate() should use the real alloc/free bytes (i.e., nr_acct) for accounting, rather than nr_bytes. The user-visible impact is that the NR_SLAB_RECLAIMABLE_B and NR_SLAB_UNRECLAIMABLE_B stats can end up being incorrect. For example, if a user allocates a 6144-byte object, then before this fix efill_obj_stock() calls mod_objcg_mlstate(..., nr_bytes=2048), even though it should account for 6144 bytes (i.e., nr_acct). When the user later frees the same object with kfree(), refill_obj_stock() calls mod_objcg_mlstate(..., nr_bytes=6144). This ends up adding 6144 to the stats, but it should be applying -6144 (i.e., nr_acct) since the object is being freed. Link: https://lkml.kernel.org/r/20260226115145.62903-1-hao.li@linux.dev Fixes: 200577f69f29 ("memcg: objcg stock trylock without irq disabling") Signed-off-by: Hao Li Acked-by: Shakeel Butt Acked-by: Johannes Weiner Cc: Michal Hocko Cc: Muchun Song Cc: Roman Gushchin Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton --- mm/memcontrol.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index a52da3a5e4fd..772bac21d155 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3086,7 +3086,7 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes, if (!local_trylock(&obj_stock.lock)) { if (pgdat) - mod_objcg_mlstate(objcg, pgdat, idx, nr_bytes); + mod_objcg_mlstate(objcg, pgdat, idx, nr_acct); nr_pages = nr_bytes >> PAGE_SHIFT; nr_bytes = nr_bytes & (PAGE_SIZE - 1); atomic_add(nr_bytes, &objcg->nr_charged_bytes);