linux-kernel - [PATCH] mm: do not call mem_cgroup_free() from within mem_cgroup

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Message-Id: <20170304025356.12265-1-tahsin@google.com>
Date:   Fri,  3 Mar 2017 18:53:56 -0800
From:   Tahsin Erdogan <tahsin@...gle.com>
To:     Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        cgroups@...r.kernel.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Tahsin Erdogan <tahsin@...gle.com>
Subject: [PATCH] mm: do not call mem_cgroup_free() from within mem_cgroup_alloc()

mem_cgroup_free() indirectly calls wb_domain_exit() which is not
prepared to deal with a struct wb_domain object that hasn't executed
wb_domain_init(). For instance, the following warning message is
printed by lockdep if alloc_percpu() fails in mem_cgroup_alloc():

  INFO: trying to register non-static key.
  the code is fine but needs lockdep annotation.
  turning off the locking correctness validator.
  CPU: 1 PID: 1950 Comm: mkdir Not tainted 4.10.0+ #151
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
  Call Trace:
   dump_stack+0x67/0x99
   register_lock_class+0x36d/0x540
   __lock_acquire+0x7f/0x1a30
   ? irq_work_queue+0x73/0x90
   ? wake_up_klogd+0x36/0x40
   ? console_unlock+0x45d/0x540
   ? vprintk_emit+0x211/0x2e0
   lock_acquire+0xcc/0x200
   ? try_to_del_timer_sync+0x60/0x60
   del_timer_sync+0x3c/0xc0
   ? try_to_del_timer_sync+0x60/0x60
   wb_domain_exit+0x14/0x20
   mem_cgroup_free+0x14/0x40
   mem_cgroup_css_alloc+0x3f9/0x620
   cgroup_apply_control_enable+0x190/0x390
   cgroup_mkdir+0x290/0x3d0
   kernfs_iop_mkdir+0x58/0x80
   vfs_mkdir+0x10e/0x1a0
   SyS_mkdirat+0xa8/0xd0
   SyS_mkdir+0x14/0x20
   entry_SYSCALL_64_fastpath+0x18/0xad

Fix mem_cgroup_alloc() by doing more granular clean up in case of
failures.

Fixes: 0b8f73e104285 ("mm: memcontrol: clean up alloc, online, offline, free functions")
Signed-off-by: Tahsin Erdogan <tahsin@...gle.com>
---
 mm/memcontrol.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c52ec893e241..9a9d5630df91 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4194,9 +4194,12 @@ static struct mem_cgroup *mem_cgroup_alloc(void)
 	idr_replace(&mem_cgroup_idr, memcg, memcg->id.id);
 	return memcg;
 fail:
+	for_each_node(node)
+		free_mem_cgroup_per_node_info(memcg, node);
+	free_percpu(memcg->stat);
 	if (memcg->id.id > 0)
 		idr_remove(&mem_cgroup_idr, memcg->id.id);
-	mem_cgroup_free(memcg);
+	kfree(memcg);
 	return NULL;
 }

-- 
2.12.0.rc1.440.g5b76565f74-goog