Commit 8380ce47 authored by Roman Gushchin's avatar Roman Gushchin Committed by Linus Torvalds
Browse files

mm: fork: fix kernel_stack memcg stats for various stack implementations 

Depending on CONFIG_VMAP_STACK and the THREAD_SIZE / PAGE_SIZE ratio the
space for task stacks can be allocated using __vmalloc_node_range(),
alloc_pages_node() and kmem_cache_alloc_node().

In the first and the second cases page->mem_cgroup pointer is set, but
in the third it's not: memcg membership of a slab page should be
determined using the memcg_from_slab_page() function, which looks at
page->slab_cache->memcg_params.memcg .  In this case, using
mod_memcg_page_state() (as in account_kernel_stack()) is incorrect:
page->mem_cgroup pointer is NULL even for pages charged to a non-root
memory cgroup.

It can lead to kernel_stack per-memcg counters permanently showing 0 on
some architectures (depending on the configuration).

In order to fix it, let's introduce a mod_memcg_obj_state() helper,
which takes a pointer to a kernel object as a first argument, uses
mem_cgroup_from_obj() to get a RCU-protected memcg pointer and calls
mod_memcg_state().  It allows to handle all possible configurations
(CONFIG_VMAP_STACK and various THREAD_SIZE/PAGE_SIZE values) without
spilling any memcg/kmem specifics into fork.c .

Note: This is a special version of the patch created for stable
backports.  It contains code from the following two patches:
  - mm: memcg/slab: introduce mem_cgroup_from_obj()
  - mm: fork: fix kernel_stack memcg stats for various stack implementations

[guro@fb.com: introduce mem_cgroup_from_obj()]
  Link: http://lkml.kernel.org/r/20200324004221.GA36662@carbon.dhcp.thefacebook.com


Fixes: 4d96ba35 ("mm: memcg/slab: stop setting page->mem_cgroup pointer for slab pages")
Signed-off-by: default avatarRoman Gushchin <guro@fb.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: default avatarShakeel Butt <shakeelb@google.com>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Bharata B Rao <bharata@linux.ibm.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/20200303233550.251375-1-guro@fb.com


Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 726b7bbe

include/linux/memcontrol.h

+12 −0
Original line number Diff line number Diff line
@@ -695,6 +695,7 @@ static inline unsigned long lruvec_page_state_local(struct lruvec *lruvec, 
void __mod_lruvec_state(struct lruvec *lruvec, enum node_stat_item idx,

			int val);

void __mod_lruvec_slab_state(void *p, enum node_stat_item idx, int val);

void mod_memcg_obj_state(void *p, int idx, int val);



static inline void mod_lruvec_state(struct lruvec *lruvec,

				    enum node_stat_item idx, int val)
@@ -1123,6 +1124,10 @@ static inline void __mod_lruvec_slab_state(void *p, enum node_stat_item idx, 
	__mod_node_page_state(page_pgdat(page), idx, val);

}



static inline void mod_memcg_obj_state(void *p, int idx, int val)

{

}



static inline

unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,

					    gfp_t gfp_mask,
@@ -1427,6 +1432,8 @@ static inline int memcg_cache_id(struct mem_cgroup *memcg) 
	return memcg ? memcg->kmemcg_id : -1;

}



struct mem_cgroup *mem_cgroup_from_obj(void *p);



#else



static inline int memcg_kmem_charge(struct page *page, gfp_t gfp, int order)
@@ -1468,6 +1475,11 @@ static inline void memcg_put_cache_ids(void) 
{

}



static inline struct mem_cgroup *mem_cgroup_from_obj(void *p)

{

       return NULL;

}



#endif /* CONFIG_MEMCG_KMEM */



#endif /* _LINUX_MEMCONTROL_H */

kernel/fork.c

+2 −2
Original line number Diff line number Diff line
@@ -397,7 +397,7 @@ static void account_kernel_stack(struct task_struct *tsk, int account) 
		mod_zone_page_state(page_zone(first_page), NR_KERNEL_STACK_KB,

				    THREAD_SIZE / 1024 * account);



		mod_memcg_page_state(first_page, MEMCG_KERNEL_STACK_KB,

		mod_memcg_obj_state(stack, MEMCG_KERNEL_STACK_KB,

				    account * (THREAD_SIZE / 1024));

	}

}

mm/memcontrol.c

+38 −0
Original line number Diff line number Diff line
@@ -777,6 +777,17 @@ void __mod_lruvec_slab_state(void *p, enum node_stat_item idx, int val) 
	rcu_read_unlock();

}



void mod_memcg_obj_state(void *p, int idx, int val)

{

	struct mem_cgroup *memcg;



	rcu_read_lock();

	memcg = mem_cgroup_from_obj(p);

	if (memcg)

		mod_memcg_state(memcg, idx, val);

	rcu_read_unlock();

}



/**

 * __count_memcg_events - account VM events in a cgroup

 * @memcg: the memory cgroup
@@ -2661,6 +2672,33 @@ static void commit_charge(struct page *page, struct mem_cgroup *memcg, 
}



#ifdef CONFIG_MEMCG_KMEM

/*

 * Returns a pointer to the memory cgroup to which the kernel object is charged.

 *

 * The caller must ensure the memcg lifetime, e.g. by taking rcu_read_lock(),

 * cgroup_mutex, etc.

 */

struct mem_cgroup *mem_cgroup_from_obj(void *p)

{

	struct page *page;



	if (mem_cgroup_disabled())

		return NULL;



	page = virt_to_head_page(p);



	/*

	 * Slab pages don't have page->mem_cgroup set because corresponding

	 * kmem caches can be reparented during the lifetime. That's why

	 * memcg_from_slab_page() should be used instead.

	 */

	if (PageSlab(page))

		return memcg_from_slab_page(page);



	/* All other pages use page->mem_cgroup */

	return page->mem_cgroup;

}



static int memcg_alloc_cache_id(void)

{

	int id, size;

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