Commit 58056f77 authored by Shakeel Butt's avatar Shakeel Butt Committed by Linus Torvalds
Browse files

memcg, kmem: further deprecate kmem.limit_in_bytes 

The deprecation process of kmem.limit_in_bytes started with the commit
0158115f ("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: default avatarShakeel Butt <shakeelb@google.com>
Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
Acked-by: default avatarRoman Gushchin <guro@fb.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Reviewed-by: default avatarMuchun Song <songmuchun@bytedance.com>
Cc: Vasily Averin <vvs@virtuozzo.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 16f6bf26

Documentation/admin-guide/cgroup-v1/memory.rst

+2 −9
Original line number Diff line number Diff line
@@ -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

-------------

mm/memcontrol.c

+5 −34
Original line number Diff line number Diff line
@@ -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)

{
@@ -3000,7 +2998,6 @@ static void obj_cgroup_uncharge_pages(struct obj_cgroup *objcg, 
static int obj_cgroup_charge_pages(struct obj_cgroup *objcg, gfp_t gfp,

				   unsigned int nr_pages)

{

	struct page_counter *counter;

	struct mem_cgroup *memcg;

	int ret;
@@ -3010,21 +3007,8 @@ static int obj_cgroup_charge_pages(struct obj_cgroup *objcg, gfp_t gfp, 
	if (ret)

		goto out;



	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) &&

	    !page_counter_try_charge(&memcg->kmem, nr_pages, &counter)) {



		/*

		 * Enforce __GFP_NOFAIL allocation because callers are not

		 * prepared to see failures and likely do not have any failure

		 * handling code.

		 */

		if (gfp & __GFP_NOFAIL) {

	if (!cgroup_subsys_on_dfl(memory_cgrp_subsys))

		page_counter_charge(&memcg->kmem, nr_pages);

			goto out;

		}

		cancel_charge(memcg, nr_pages);

		ret = -ENOMEM;

	}

out:

	css_put(&memcg->css);
@@ -3714,17 +3698,6 @@ 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 +3763,8 @@ 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);