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Commit ec9f0238 authored by Roman Gushchin's avatar Roman Gushchin Committed by Linus Torvalds
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mm: workingset: fix vmstat counters for shadow nodes 

Memcg counters for shadow nodes are broken because the memcg pointer is
obtained in a wrong way. The following approach is used:
        virt_to_page(xa_node)->mem_cgroup

Since commit 4d96ba35 ("mm: memcg/slab: stop setting
page->mem_cgroup pointer for slab pages") page->mem_cgroup pointer isn't
set for slab pages, so memcg_from_slab_page() should be used instead.

Also I doubt that it ever worked correctly: virt_to_head_page() should
be used instead of virt_to_page().  Otherwise objects residing on tail
pages are not accounted, because only the head page contains a valid
mem_cgroup pointer.  That was a case since the introduction of these
counters by the commit 68d48e6a ("mm: workingset: add vmstat counter
for shadow nodes").

Link: http://lkml.kernel.org/r/20190801233532.138743-1-guro@fb.com


Fixes: 4d96ba35 ("mm: memcg/slab: stop setting page->mem_cgroup pointer for slab pages")
Signed-off-by: default avatarRoman Gushchin <guro@fb.com>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 95153169

include/linux/memcontrol.h

+19 −0
Original line number Diff line number Diff line
@@ -668,6 +668,7 @@ 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);



static inline void mod_lruvec_state(struct lruvec *lruvec,

				    enum node_stat_item idx, int val)
@@ -1072,6 +1073,14 @@ static inline void mod_lruvec_page_state(struct page *page, 
	mod_node_page_state(page_pgdat(page), idx, val);

}



static inline void __mod_lruvec_slab_state(void *p, enum node_stat_item idx,

					   int val)

{

	struct page *page = virt_to_head_page(p);



	__mod_node_page_state(page_pgdat(page), idx, val);

}



static inline

unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,

					    gfp_t gfp_mask,
@@ -1159,6 +1168,16 @@ static inline void __dec_lruvec_page_state(struct page *page, 
	__mod_lruvec_page_state(page, idx, -1);

}



static inline void __inc_lruvec_slab_state(void *p, enum node_stat_item idx)

{

	__mod_lruvec_slab_state(p, idx, 1);

}



static inline void __dec_lruvec_slab_state(void *p, enum node_stat_item idx)

{

	__mod_lruvec_slab_state(p, idx, -1);

}



/* idx can be of type enum memcg_stat_item or node_stat_item */

static inline void inc_memcg_state(struct mem_cgroup *memcg,

				   int idx)

mm/memcontrol.c

+20 −0
Original line number Diff line number Diff line
@@ -768,6 +768,26 @@ void __mod_lruvec_state(struct lruvec *lruvec, enum node_stat_item idx, 
	__this_cpu_write(pn->lruvec_stat_cpu->count[idx], x);

}



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

{

	struct page *page = virt_to_head_page(p);

	pg_data_t *pgdat = page_pgdat(page);

	struct mem_cgroup *memcg;

	struct lruvec *lruvec;



	rcu_read_lock();

	memcg = memcg_from_slab_page(page);



	/* Untracked pages have no memcg, no lruvec. Update only the node */

	if (!memcg || memcg == root_mem_cgroup) {

		__mod_node_page_state(pgdat, idx, val);

	} else {

		lruvec = mem_cgroup_lruvec(pgdat, memcg);

		__mod_lruvec_state(lruvec, idx, val);

	}

	rcu_read_unlock();

}



/**

 * __count_memcg_events - account VM events in a cgroup

 * @memcg: the memory cgroup

mm/workingset.c

+4 −6
Original line number Diff line number Diff line
@@ -380,14 +380,12 @@ void workingset_update_node(struct xa_node *node) 
	if (node->count && node->count == node->nr_values) {

		if (list_empty(&node->private_list)) {

			list_lru_add(&shadow_nodes, &node->private_list);

			__inc_lruvec_page_state(virt_to_page(node),

						WORKINGSET_NODES);

			__inc_lruvec_slab_state(node, WORKINGSET_NODES);

		}

	} else {

		if (!list_empty(&node->private_list)) {

			list_lru_del(&shadow_nodes, &node->private_list);

			__dec_lruvec_page_state(virt_to_page(node),

						WORKINGSET_NODES);

			__dec_lruvec_slab_state(node, WORKINGSET_NODES);

		}

	}

}
@@ -480,7 +478,7 @@ static enum lru_status shadow_lru_isolate(struct list_head *item, 
	}



	list_lru_isolate(lru, item);

	__dec_lruvec_page_state(virt_to_page(node), WORKINGSET_NODES);

	__dec_lruvec_slab_state(node, WORKINGSET_NODES);



	spin_unlock(lru_lock);
@@ -503,7 +501,7 @@ static enum lru_status shadow_lru_isolate(struct list_head *item, 
	 * shadow entries we were tracking ...

	 */

	xas_store(&xas, NULL);

	__inc_lruvec_page_state(virt_to_page(node), WORKINGSET_NODERECLAIM);

	__inc_lruvec_slab_state(node, WORKINGSET_NODERECLAIM);



out_invalid:

	xa_unlock_irq(&mapping->i_pages);