The patch titled
Subject: memcg: drop kmem.limit_in_bytes
has been added to the -mm mm-unstable branch. Its filename is
memcg-drop-kmemlimit_in_bytes.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/memcg-drop-kmemlimit_in_bytes.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Michal Hocko <mhocko@xxxxxxxx>
Subject: memcg: drop kmem.limit_in_bytes
Date: Tue, 4 Jul 2023 13:52:40 +0200
kmem.limit_in_bytes (v1 way to limit kernel memory usage) has been
deprecated since 58056f77502f ("memcg, kmem: further deprecate
kmem.limit_in_bytes") merged in 5.16. We haven't heard about any serious
users since then but it seems that the mere presence of the file is
causing more harm than good. We (SUSE) have had several bug reports from
customers where Docker based containers started to fail because a write to
kmem.limit_in_bytes has failed.
This was unexpected because runc code only expects ENOENT (kmem disabled)
or EBUSY (tasks already running within cgroup). So a new error code was
unexpected and the whole container startup failed. This has been later
addressed by
https://github.com/opencontainers/runc/commit/52390d68040637dfc77f9fda6bbe70952423d380
so current Docker runtimes do not suffer from the problem anymore. There
are still older version of Docker in use and likely hard to get rid of
completely.
Address this by wiping out the file completely and effectively get back to
pre 4.5 era and CONFIG_MEMCG_KMEM=n configuration.
I would recommend backporting to stable trees which have picked up
58056f77502f ("memcg, kmem: further deprecate kmem.limit_in_bytes").
Link: https://lkml.kernel.org/r/20230704115240.14672-1-mhocko@xxxxxxxxxx
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/admin-guide/cgroup-v1/memory.rst | 2 --
mm/memcontrol.c | 13 -------------
2 files changed, 15 deletions(-)
--- a/Documentation/admin-guide/cgroup-v1/memory.rst~memcg-drop-kmemlimit_in_bytes
+++ a/Documentation/admin-guide/cgroup-v1/memory.rst
@@ -92,8 +92,6 @@ Brief summary of control files.
memory.oom_control set/show oom controls.
memory.numa_stat show the number of memory usage per numa
node
- memory.kmem.limit_in_bytes This knob is deprecated and writing to
- it will return -ENOTSUPP.
memory.kmem.usage_in_bytes show current kernel memory allocation
memory.kmem.failcnt show the number of kernel memory usage
hits limits
--- a/mm/memcontrol.c~memcg-drop-kmemlimit_in_bytes
+++ a/mm/memcontrol.c
@@ -3708,9 +3708,6 @@ static u64 mem_cgroup_read_u64(struct cg
case _MEMSWAP:
counter = &memcg->memsw;
break;
- case _KMEM:
- counter = &memcg->kmem;
- break;
case _TCP:
counter = &memcg->tcpmem;
break;
@@ -3871,10 +3868,6 @@ static ssize_t mem_cgroup_write(struct k
case _MEMSWAP:
ret = mem_cgroup_resize_max(memcg, nr_pages, true);
break;
- case _KMEM:
- /* kmem.limit_in_bytes is deprecated. */
- ret = -EOPNOTSUPP;
- break;
case _TCP:
ret = memcg_update_tcp_max(memcg, nr_pages);
break;
@@ -5086,12 +5079,6 @@ static struct cftype mem_cgroup_legacy_f
},
#endif
{
- .name = "kmem.limit_in_bytes",
- .private = MEMFILE_PRIVATE(_KMEM, RES_LIMIT),
- .write = mem_cgroup_write,
- .read_u64 = mem_cgroup_read_u64,
- },
- {
.name = "kmem.usage_in_bytes",
.private = MEMFILE_PRIVATE(_KMEM, RES_USAGE),
.read_u64 = mem_cgroup_read_u64,
_
Patches currently in -mm which might be from mhocko@xxxxxxxx are
memcg-drop-kmemlimit_in_bytes.patch
