>From ae12af515da0d557c25f86e89b0251d2da2ad8dc Mon Sep 17 00:00:00 2001 From: Shakeel Butt Date: Fri, 5 Nov 2021 13:37:44 -0700 Subject: [PATCH] memcg, kmem: further deprecate kmem.limit_in_bytes update for debugging by Fengwei The deprecation process of kmem.limit_in_bytes started with the commit 0158115f702 ("memcg, kmem: deprecate kmem.limit_in_bytes") which also explains in detail the motivation behind the deprecation. To summarize, it is the unexpected behavior on hitting the kmem limit. This patch moves the deprecation process to the next stage by disallowing to set the kmem limit. In future we might just remove the kmem.limit_in_bytes file completely. [akpm@linux-foundation.org: s/ENOTSUPP/EOPNOTSUPP/] [arnd@arndb.de: mark cancel_charge() inline] Link: https://lkml.kernel.org/r/20211022070542.679839-1-arnd@kernel.org Link: https://lkml.kernel.org/r/20211019153408.2916808-1-shakeelb@google.com Signed-off-by: Shakeel Butt Signed-off-by: Arnd Bergmann Acked-by: Roman Gushchin Acked-by: Michal Hocko Reviewed-by: Muchun Song Cc: Vasily Averin Cc: Johannes Weiner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- .../admin-guide/cgroup-v1/memory.rst | 11 ++-------- mm/memcontrol.c | 21 +++---------------- 2 files changed, 5 insertions(+), 27 deletions(-) diff --git a/Documentation/admin-guide/cgroup-v1/memory.rst b/Documentation/admin-guide/cgroup-v1/memory.rst index 41191b5fb69d9..faac50149a222 100644 --- a/Documentation/admin-guide/cgroup-v1/memory.rst +++ b/Documentation/admin-guide/cgroup-v1/memory.rst @@ -87,10 +87,8 @@ 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 set/show hard limit for kernel memory - This knob is deprecated and shouldn't be - used. It is planned that this be removed in - the foreseeable future. + 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 @@ -518,11 +516,6 @@ will be charged as a new owner of it. charged file caches. Some out-of-use page caches may keep charged until memory pressure happens. If you want to avoid that, force_empty will be useful. - Also, note that when memory.kmem.limit_in_bytes is set the charges due to - kernel pages will still be seen. This is not considered a failure and the - write will still return success. In this case, it is expected that - memory.kmem.usage_in_bytes == memory.usage_in_bytes. - 5.2 stat file ------------- diff --git a/mm/memcontrol.c b/mm/memcontrol.c index e092cce3c96e7..22c2f97773eeb 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2771,8 +2771,7 @@ static inline int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask, return try_charge_memcg(memcg, gfp_mask, nr_pages); } -#if defined(CONFIG_MEMCG_KMEM) || defined(CONFIG_MMU) -static void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages) +static inline void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages) { if (mem_cgroup_is_root(memcg)) return; @@ -2781,7 +2780,6 @@ static void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages) if (do_memsw_account()) page_counter_uncharge(&memcg->memsw, nr_pages); } -#endif static void commit_charge(struct page *page, struct mem_cgroup *memcg) { @@ -3714,17 +3712,6 @@ static void memcg_offline_kmem(struct mem_cgroup *memcg) } #endif /* CONFIG_MEMCG_KMEM */ -static int memcg_update_kmem_max(struct mem_cgroup *memcg, - unsigned long max) -{ - int ret; - - mutex_lock(&memcg_max_mutex); - ret = page_counter_set_max(&memcg->kmem, max); - mutex_unlock(&memcg_max_mutex); - return ret; -} - static int memcg_update_tcp_max(struct mem_cgroup *memcg, unsigned long max) { int ret; @@ -3790,10 +3777,8 @@ static ssize_t mem_cgroup_write(struct kernfs_open_file *of, 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. " - "Please report your usecase to linux-mm@kvack.org if you " - "depend on this functionality.\n"); - ret = memcg_update_kmem_max(memcg, nr_pages); + /* kmem.limit_in_bytes is deprecated. */ + ret = -EOPNOTSUPP; break; case _TCP: ret = memcg_update_tcp_max(memcg, nr_pages); -- 2.30.2