--- /dev/null
+From 86327e8eb94c52eca4f93cfece2e29d1bf52acbf Mon Sep 17 00:00:00 2001
+From: Michal Hocko <mhocko@suse.com>
+Date: Tue, 4 Jul 2023 13:52:40 +0200
+Subject: memcg: drop kmem.limit_in_bytes
+
+From: Michal Hocko <mhocko@suse.com>
+
+commit 86327e8eb94c52eca4f93cfece2e29d1bf52acbf upstream.
+
+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 thatn 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").
+
+[mhocko@suse.com: restore _KMEM switch case]
+ Link: https://lkml.kernel.org/r/ZKe5wxdbvPi5Cwd7@dhcp22.suse.cz
+Link: https://lkml.kernel.org/r/20230704115240.14672-1-mhocko@kernel.org
+Signed-off-by: Michal Hocko <mhocko@suse.com>
+Acked-by: Shakeel Butt <shakeelb@google.com>
+Acked-by: Johannes Weiner <hannes@cmpxchg.org>
+Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
+Cc: Muchun Song <muchun.song@linux.dev>
+Cc: Tejun Heo <tj@kernel.org>
+Cc: <stable@vger.kernel.org>
+Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ Documentation/admin-guide/cgroup-v1/memory.rst | 2 --
+ mm/memcontrol.c | 10 ----------
+ 2 files changed, 12 deletions(-)
+
+--- a/Documentation/admin-guide/cgroup-v1/memory.rst
++++ b/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
++++ b/mm/memcontrol.c
+@@ -3871,10 +3871,6 @@ 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 +5082,6 @@ 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,
--- /dev/null
+From 4597648fddeadef5877610d693af11906aa666ac Mon Sep 17 00:00:00 2001
+From: Michal Hocko <mhocko@suse.com>
+Date: Thu, 21 Sep 2023 09:38:29 +0200
+Subject: mm, memcg: reconsider kmem.limit_in_bytes deprecation
+
+From: Michal Hocko <mhocko@suse.com>
+
+commit 4597648fddeadef5877610d693af11906aa666ac upstream.
+
+This reverts commits 86327e8eb94c ("memcg: drop kmem.limit_in_bytes") and
+partially reverts 58056f77502f ("memcg, kmem: further deprecate
+kmem.limit_in_bytes") which have incrementally removed support for the
+kernel memory accounting hard limit. Unfortunately it has turned out that
+there is still userspace depending on the existence of
+memory.kmem.limit_in_bytes [1]. The underlying functionality is not
+really required but the non-existent file just confuses the userspace
+which fails in the result. The patch to fix this on the userspace side
+has been submitted but it is hard to predict how it will propagate through
+the maze of 3rd party consumers of the software.
+
+Now, reverting alone 86327e8eb94c is not an option because there is
+another set of userspace which cannot cope with ENOTSUPP returned when
+writing to the file. Therefore we have to go and revisit 58056f77502f as
+well. There are two ways to go ahead. Either we give up on the
+deprecation and fully revert 58056f77502f as well or we can keep
+kmem.limit_in_bytes but make the write a noop and warn about the fact.
+This should work for both known breaking workloads which depend on the
+existence but do not depend on the hard limit enforcement.
+
+Note to backporters to stable trees. a8c49af3be5f ("memcg: add per-memcg
+total kernel memory stat") introduced in 4.18 has added memcg_account_kmem
+so the accounting is not done by obj_cgroup_charge_pages directly for v1
+anymore. Prior kernels need to add it explicitly (thanks to Johannes for
+pointing this out).
+
+[akpm@linux-foundation.org: fix build - remove unused local]
+Link: http://lkml.kernel.org/r/20230920081101.GA12096@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net [1]
+Link: https://lkml.kernel.org/r/ZRE5VJozPZt9bRPy@dhcp22.suse.cz
+Fixes: 86327e8eb94c ("memcg: drop kmem.limit_in_bytes")
+Fixes: 58056f77502f ("memcg, kmem: further deprecate kmem.limit_in_bytes")
+Signed-off-by: Michal Hocko <mhocko@suse.com>
+Acked-by: Shakeel Butt <shakeelb@google.com>
+Acked-by: Johannes Weiner <hannes@cmpxchg.org>
+Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+Cc: Jeremi Piotrowski <jpiotrowski@linux.microsoft.com>
+Cc: Muchun Song <muchun.song@linux.dev>
+Cc: Roman Gushchin <roman.gushchin@linux.dev>
+Cc: Tejun heo <tj@kernel.org>
+Cc: <stable@vger.kernel.org>
+Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ Documentation/admin-guide/cgroup-v1/memory.rst | 7 +++++++
+ mm/memcontrol.c | 13 +++++++++++++
+ 2 files changed, 20 insertions(+)
+
+--- a/Documentation/admin-guide/cgroup-v1/memory.rst
++++ b/Documentation/admin-guide/cgroup-v1/memory.rst
+@@ -92,6 +92,13 @@ 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 Deprecated knob to set and read the kernel
++ memory hard limit. Kernel hard limit is not
++ supported since 5.16. Writing any value to
++ do file will not have any effect same as if
++ nokmem kernel parameter was specified.
++ Kernel memory is still charged and reported
++ by memory.kmem.usage_in_bytes.
+ 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
++++ b/mm/memcontrol.c
+@@ -3871,6 +3871,13 @@ static ssize_t mem_cgroup_write(struct k
+ case _MEMSWAP:
+ ret = mem_cgroup_resize_max(memcg, nr_pages, true);
+ break;
++ case _KMEM:
++ pr_warn_once("kmem.limit_in_bytes is deprecated and will be removed. "
++ "Writing any value to this file has no effect. "
++ "Please report your usecase to linux-mm@kvack.org if you "
++ "depend on this functionality.\n");
++ ret = 0;
++ break;
+ case _TCP:
+ ret = memcg_update_tcp_max(memcg, nr_pages);
+ break;
+@@ -5082,6 +5089,12 @@ 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,
projects / thirdparty / kernel / stable-queue.git / commitdiff
