The commit is pushed to "branch-rh7-3.10.0-1160.90.1.vz7.200.x-ovz" and will
appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-1160.90.1.vz7.200.4
------>
commit f6ed14e332eb3286cfe15aedcaa7fe333de20f6b
Author: Kirill Tkhai <ktk...@virtuozzo.com>
Date: Wed Jul 5 14:39:49 2023 +0800
ms/memcg: remove memcg_cgroup::id from IDR on mem_cgroup_css_alloc() failure
In case of memcg_online_kmem() failure, memcg_cgroup::id remains hashed
in mem_cgroup_idr even after memcg memory is freed. This leads to leak
of ID in mem_cgroup_idr.
This patch adds removal into mem_cgroup_css_alloc(), which fixes the
problem. For better readability, it adds a generic helper which is used
in mem_cgroup_alloc() and mem_cgroup_id_put_many() as well.
Link:
http://lkml.kernel.org/r/152354470916.22460.14397070748001974638.stgit@localhost.localdomain
Fixes 73f576c04b94 ("mm: memcontrol: fix cgroup creation failure after many
small jobs")
Signed-off-by: Kirill Tkhai <ktk...@virtuozzo.com>
Acked-by: Johannes Weiner <han...@cmpxchg.org>
Acked-by: Vladimir Davydov <vdavydov....@gmail.com>
Cc: Michal Hocko <mho...@kernel.org>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Changes:
- skip hunk in mem_cgroup_css_alloc as there is no such error path yet,
patch is not strictly required but better have it as a small cleanup
https://jira.vzint.dev/browse/PSBM-147036
(cherry picked from commit 7e97de0b033bcac4fa9a35cef72e0c06e6a22c67)
Signed-off-by: Pavel Tikhomirov <ptikhomi...@virtuozzo.com>
=================
Patchset description:
memcg: release id when offlinging cgroup
We see that container user can deplete memory cgroup ids on the system
(64k) and prevent further memory cgroup creation. In crash collected by
our customer in such a situation we see that mem_cgroup_idr is full of
cgroups from one container with same exact path (cgroup of docker
service), cgroups are not released because they have kmem charges, this
kmem charge is for a tmpfs dentry allocated from this cgroup. (And on
vz7 kernel it seems that such a dentry is only released after umounting
tmpfs or removing the corresponding file from tmpfs.)
So there is a valid way to hold kmem cgroup for a long time. Similar
thing was mentioned in mainstream with page cache holding kmem cgroup
for a long time. And they proposed a way to deal with it - just release
cgroup id early so that one can allocate new cgroups immediately.
Reproduce:
https://git.vzint.dev/users/ptikhomirov/repos/helpers/browse/memcg-related/test-mycg-tmpfs.sh
After this fix the number of memory cgroups in /proc/cgroups can now
show > 64k as we allow to leave memory cgroups hanging while releasing
their ids.
Note: Maybe it's a bad idea to allow container to eat kernel
memory with such a hanging cgroups, but yet I don't have better ideas.
https://jira.vzint.dev/browse/PSBM-147473
https://jira.vzint.dev/browse/PSBM-147036
---
mm/memcontrol.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0ff99bf5abdb..5c0a7dc32908 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6671,6 +6671,14 @@ unsigned short mem_cgroup_id(struct mem_cgroup *memcg)
return memcg->id.id;
}
+static void mem_cgroup_id_remove(struct mem_cgroup *memcg)
+{
+ if (memcg->id.id > 0) {
+ idr_remove(&mem_cgroup_idr, memcg->id.id);
+ memcg->id.id = 0;
+ }
+}
+
static void mem_cgroup_id_get_many(struct mem_cgroup *memcg, unsigned int n)
{
atomic_add(n, &memcg->id.ref);
@@ -6697,8 +6705,7 @@ static struct mem_cgroup *mem_cgroup_id_get_online(struct
mem_cgroup *memcg)
static void mem_cgroup_id_put_many(struct mem_cgroup *memcg, unsigned int n)
{
if (atomic_sub_and_test(n, &memcg->id.ref)) {
- idr_remove(&mem_cgroup_idr, memcg->id.id);
- memcg->id.id = 0;
+ mem_cgroup_id_remove(memcg);
/* Memcg ID pins CSS */
css_put(&memcg->css);
@@ -6808,8 +6815,7 @@ static struct mem_cgroup *mem_cgroup_alloc(void)
for_each_node(node)
free_mem_cgroup_per_zone_info(memcg, node);
- if (memcg->id.id > 0)
- idr_remove(&mem_cgroup_idr, memcg->id.id);
+ mem_cgroup_id_remove(memcg);
fail:
kfree(memcg);
return NULL;
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