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 11870ae0f7b6083816d7532b8b39e86985a0b3de
Author: Vladimir Davydov <vdavy...@virtuozzo.com>
Date: Wed Jul 5 14:39:47 2023 +0800
ms/mm: memcontrol: fix memcg id ref counter on swap charge move
Since commit 73f576c04b94 ("mm: memcontrol: fix cgroup creation failure
after many small jobs") swap entries do not pin memcg->css.refcnt
directly. Instead, they pin memcg->id.ref. So we should adjust the
reference counters accordingly when moving swap charges between cgroups.
Fixes: 73f576c04b941 ("mm: memcontrol: fix cgroup creation failure after
many small jobs")
Link:
http://lkml.kernel.org/r/9ce297c64954a42dc90b543bc76106c4a94f07e8.1470219853.git.vdavy...@virtuozzo.com
Signed-off-by: Vladimir Davydov <vdavy...@virtuozzo.com>
Acked-by: Michal Hocko <mho...@suse.com>
Acked-by: Johannes Weiner <han...@cmpxchg.org>
Cc: <sta...@vger.kernel.org> [3.19+]
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Changes:
original patch also did:
- css_put_many(&mc.from->css, mc.moved_swap);
+ css_put_many(&mc.to->css, mc.moved_swap);
but this change seems strange and unrelated to me, let's skip it.
https://jira.vzint.dev/browse/PSBM-147036
(cherry picked from commit 615d66c37c755c49ce022c9e5ac0875d27d2603d)
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 | 24 +++++++++++++++++++-----
1 file changed, 19 insertions(+), 5 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index d106e8f64997..f86c395fe8ee 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6671,9 +6671,9 @@ unsigned short mem_cgroup_id(struct mem_cgroup *memcg)
return memcg->id.id;
}
-static void mem_cgroup_id_get(struct mem_cgroup *memcg)
+static void mem_cgroup_id_get_many(struct mem_cgroup *memcg, unsigned int n)
{
- atomic_inc(&memcg->id.ref);
+ atomic_add(n, &memcg->id.ref);
}
static struct mem_cgroup *mem_cgroup_id_get_online(struct mem_cgroup *memcg)
@@ -6694,9 +6694,9 @@ static struct mem_cgroup *mem_cgroup_id_get_online(struct
mem_cgroup *memcg)
return memcg;
}
-static void mem_cgroup_id_put(struct mem_cgroup *memcg)
+static void mem_cgroup_id_put_many(struct mem_cgroup *memcg, unsigned int n)
{
- if (atomic_dec_and_test(&memcg->id.ref)) {
+ if (atomic_sub_and_test(n, &memcg->id.ref)) {
idr_remove(&mem_cgroup_idr, memcg->id.id);
memcg->id.id = 0;
@@ -6705,6 +6705,16 @@ static void mem_cgroup_id_put(struct mem_cgroup *memcg)
}
}
+static inline void mem_cgroup_id_get(struct mem_cgroup *memcg)
+{
+ mem_cgroup_id_get_many(memcg, 1);
+}
+
+static inline void mem_cgroup_id_put(struct mem_cgroup *memcg)
+{
+ mem_cgroup_id_put_many(memcg, 1);
+}
+
/**
* mem_cgroup_from_id - look up a memcg from a memcg id
* @id: the memcg id to look up
@@ -7439,6 +7449,8 @@ static void __mem_cgroup_clear_mc(void)
if (!mem_cgroup_is_root(mc.from))
page_counter_uncharge(&mc.from->memsw, mc.moved_swap);
+ mem_cgroup_id_put_many(mc.from, mc.moved_swap);
+
for (i = 0; i < mc.moved_swap; i++)
css_put(&mc.from->css);
@@ -7449,7 +7461,9 @@ static void __mem_cgroup_clear_mc(void)
*/
page_counter_uncharge(&mc.to->memory, mc.moved_swap);
}
- /* we've already done css_get(mc.to) */
+
+ mem_cgroup_id_get_many(mc.to, mc.moved_swap);
+
mc.moved_swap = 0;
}
if (do_swap_account) {
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