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Commit 2c80cd57 authored by Sahitya Tummala's avatar Sahitya Tummala Committed by Linus Torvalds
Browse files

mm/list_lru.c: fix list_lru_count_node() to be race free 

list_lru_count_node() iterates over all memcgs to get the total number of
entries on the node but it can race with memcg_drain_all_list_lrus(),
which migrates the entries from a dead cgroup to another.  This can return
incorrect number of entries from list_lru_count_node().

Fix this by keeping track of entries per node and simply return it in
list_lru_count_node().

Link: http://lkml.kernel.org/r/1498707555-30525-1-git-send-email-stummala@codeaurora.org


Signed-off-by: default avatarSahitya Tummala <stummala@codeaurora.org>
Acked-by: default avatarVladimir Davydov <vdavydov.dev@gmail.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Alexander Polakov <apolyakov@beget.ru>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 32e4e6d5

include/linux/list_lru.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -44,6 +44,7 @@ struct list_lru_node { 
	/* for cgroup aware lrus points to per cgroup lists, otherwise NULL */

	/* for cgroup aware lrus points to per cgroup lists, otherwise NULL */

	struct list_lru_memcg	*memcg_lrus;

	struct list_lru_memcg	*memcg_lrus;

#endif

#endif

	long nr_items;

} ____cacheline_aligned_in_smp;

} ____cacheline_aligned_in_smp;





struct list_lru {

struct list_lru {

mm/list_lru.c

+6 −8
Original line number Original line Diff line number Diff line
@@ -117,6 +117,7 @@ bool list_lru_add(struct list_lru *lru, struct list_head *item) 
		l = list_lru_from_kmem(nlru, item);

		l = list_lru_from_kmem(nlru, item);

		list_add_tail(item, &l->list);

		list_add_tail(item, &l->list);

		l->nr_items++;

		l->nr_items++;

		nlru->nr_items++;

		spin_unlock(&nlru->lock);

		spin_unlock(&nlru->lock);

		return true;

		return true;

	}

	}
@@ -136,6 +137,7 @@ bool list_lru_del(struct list_lru *lru, struct list_head *item) 
		l = list_lru_from_kmem(nlru, item);

		l = list_lru_from_kmem(nlru, item);

		list_del_init(item);

		list_del_init(item);

		l->nr_items--;

		l->nr_items--;

		nlru->nr_items--;

		spin_unlock(&nlru->lock);

		spin_unlock(&nlru->lock);

		return true;

		return true;

	}

	}
@@ -183,15 +185,10 @@ EXPORT_SYMBOL_GPL(list_lru_count_one); 




unsigned long list_lru_count_node(struct list_lru *lru, int nid)

unsigned long list_lru_count_node(struct list_lru *lru, int nid)

{

{

	long count = 0;

	struct list_lru_node *nlru;

	int memcg_idx;





	count += __list_lru_count_one(lru, nid, -1);

	nlru = &lru->node[nid];

	if (list_lru_memcg_aware(lru)) {

	return nlru->nr_items;

		for_each_memcg_cache_index(memcg_idx)

			count += __list_lru_count_one(lru, nid, memcg_idx);

	}

	return count;

}

}

EXPORT_SYMBOL_GPL(list_lru_count_node);

EXPORT_SYMBOL_GPL(list_lru_count_node);
@@ -226,6 +223,7 @@ __list_lru_walk_one(struct list_lru *lru, int nid, int memcg_idx, 
			assert_spin_locked(&nlru->lock);

			assert_spin_locked(&nlru->lock);

		case LRU_REMOVED:

		case LRU_REMOVED:

			isolated++;

			isolated++;

			nlru->nr_items--;

			/*

			/*

			 * If the lru lock has been dropped, our list

			 * If the lru lock has been dropped, our list

			 * traversal is now invalid and so we have to

			 * traversal is now invalid and so we have to