[Sorry for a late reply - was offline for few days]
On Thu 21-05-20 17:58:55, Johannes Weiner wrote:
On Thu, May 21, 2020 at 01:06:28PM -0700, Hugh Dickins wrote:
[...]
From d9e7ed15d1c9248a3fd99e35e82437549154dac7 Mon Sep 17 00:00:00 2001
From: Johannes Weiner hannes@cmpxchg.org Date: Thu, 21 May 2020 17:44:25 -0400 Subject: [PATCH] mm: memcontrol: prepare swap controller setup for integration fix
Fix crash with cgroup_disable=memory:
- mkfs -t ext4 /dev/disk/by-id/ata-TOSHIBA_MG04ACA100N_Y8NRK0BPF6XF
mke2fs 1.43.8 (1-Jan-2018) Creating filesystem with 244190646 4k blocks and 61054976 inodes Filesystem UUID: 3bb1a285-2cb4-44b4-b6e8-62548f3ac620 Superblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968, 102400000, 214990848 Allocating group tables: 0/7453 done Writing inode tables: 0/7453 done Creating journal (262144 blocks): [ 35.502102] BUG: kernel NULL pointer dereference, address: 000000c8 [ 35.508372] #PF: supervisor read access in kernel mode [ 35.513506] #PF: error_code(0x0000) - not-present page [ 35.518638] *pde = 00000000 [ 35.521514] Oops: 0000 [#1] SMP [ 35.524652] CPU: 0 PID: 145 Comm: kswapd0 Not tainted 5.7.0-rc6-next-20200519+ #1 [ 35.532121] Hardware name: Supermicro SYS-5019S-ML/X11SSH-F, BIOS 2.2 05/23/2018 [ 35.539507] EIP: mem_cgroup_get_nr_swap_pages+0x28/0x60
Swap accounting used to be implied-disabled when the cgroup controller was disabled. Restore that for the new cgroup_memory_noswap, so that we bail out of this function instead of dereferencing a NULL memcg.
Reported-by: Naresh Kamboju naresh.kamboju@linaro.org Debugged-by: Hugh Dickins hughd@google.com Debugged-by: Michal Hocko mhocko@kernel.org Signed-off-by: Johannes Weiner hannes@cmpxchg.org
Yes this looks better. I hope to get to your series soon to have the full picture finally.
mm/memcontrol.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 3e000a316b59..e3b785d6e771 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -7075,7 +7075,11 @@ static struct cftype memsw_files[] = { static int __init mem_cgroup_swap_init(void) {
- if (mem_cgroup_disabled() || cgroup_memory_noswap)
- /* No memory control -> no swap control */
- if (mem_cgroup_disabled())
cgroup_memory_noswap = true;- if (cgroup_memory_noswap) return 0;
WARN_ON(cgroup_add_dfl_cftypes(&memory_cgrp_subsys, swap_files)); -- 2.26.2