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

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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: Sahitya Tummala <stummala@codeaurora.org>
Acked-by: Vladimir 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Sahitya Tummala 2017-07-10 15:49:57 -07:00 committed by Linus Torvalds
parent 32e4e6d5cb
commit 2c80cd57c7
2 changed files with 7 additions and 8 deletions
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1
include/linux/list_lru.h
View File

@ -44,6 +44,7 @@ struct list_lru_node {
/* for cgroup aware lrus points to per cgroup lists, otherwise NULL */
struct list_lru_memcg *memcg_lrus;
#endif
long nr_items;
} ____cacheline_aligned_in_smp;
struct list_lru {

14
mm/list_lru.c
View File

@ -117,6 +117,7 @@ bool list_lru_add(struct list_lru *lru, struct list_head *item)
l = list_lru_from_kmem(nlru, item);
list_add_tail(item, &l->list);
l->nr_items++;
nlru->nr_items++;
spin_unlock(&nlru->lock);
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);
list_del_init(item);
l->nr_items--;
nlru->nr_items--;
spin_unlock(&nlru->lock);
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)
{
long count = 0;
int memcg_idx;
struct list_lru_node *nlru;
count += __list_lru_count_one(lru, nid, -1);
if (list_lru_memcg_aware(lru)) {
for_each_memcg_cache_index(memcg_idx)
count += __list_lru_count_one(lru, nid, memcg_idx);
}
return count;
nlru = &lru->node[nid];
return nlru->nr_items;
}
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);
case LRU_REMOVED:
isolated++;
nlru->nr_items--;
/*
* If the lru lock has been dropped, our list
* traversal is now invalid and so we have to