From 00a22cdd58bd9cadee0f171f23bfcd735e4ce638 Mon Sep 17 00:00:00 2001 From: Thadeu Lima de Souza Cascardo Date: Thu, 11 Mar 2021 11:41:17 -0300 Subject: [PATCH] UBUNTU: SAUCE: Revert "mm: memcg/slab: optimize objcg stock draining" BugLink: https://bugs.launchpad.net/bugs/1918668 This reverts commit 482b2134fda0a74aff66147e777233caede3a0bc, which is commit 3de7d4f25a7438f09fef4e71ef111f1805cd8e7c upstream. It is supposed to fix f2fe7b09a52b ("mm: memcg/slab: charge individual slab objects instead of pages"), which is not present in groovy kernel at all. It leads to NULL pointer derefences like: [ 10.012503] BUG: kernel NULL pointer dereference, address: 0000000000000518 [ 10.030761] #PF: supervisor read access in kernel mode [ 10.042518] #PF: error_code(0x0000) - not-present page [ 10.050165] PGD 0 P4D 0 [ 10.077050] Oops: 0000 [#1] SMP PTI [ 10.081927] CPU: 0 PID: 516 Comm: kexec-load Tainted: G W 5.8.0-45-generic #51 [ 10.092486] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-1 04/01/2014 [ 10.103510] RIP: 0010:__mod_memcg_state.part.0+0xc/0x90 This is possibly caused by a refcount going past 0: [ 5.792689] percpu ref (css_release) <= 0 (-81) after switching to atomic [ 5.792747] WARNING: CPU: 2 PID: 24 at lib/percpu-refcount.c:161 percpu_ref_switch_to_atomic_rcu+0x147/0x160 Signed-off-by: Thadeu Lima de Souza Cascardo Acked-by: Kleber Sacilotto de Souza Acked-by: Tim Gardner Signed-off-by: Kelsey Skunberg --- mm/memcontrol.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index fdfae074ac917..bf0fc20ae20b3 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2936,7 +2936,9 @@ void __memcg_kmem_uncharge(struct mem_cgroup *memcg, unsigned int nr_pages) if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) page_counter_uncharge(&memcg->kmem, nr_pages); - refill_stock(memcg, nr_pages); + page_counter_uncharge(&memcg->memory, nr_pages); + if (do_memsw_account()) + page_counter_uncharge(&memcg->memsw, nr_pages); } /**