From: Vladimir Davydov <vdavydov@parallels.com>
To: <akpm@linux-foundation.org>
Cc: <iamjoonsoo.kim@lge.com>, <cl@linux.com>, <rientjes@google.com>,
<penberg@kernel.org>, <hannes@cmpxchg.org>, <mhocko@suse.cz>,
<linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>
Subject: [PATCH -mm] slub: kmem_cache_shrink: check if partial list is empty under list_lock
Date: Tue, 24 Jun 2014 13:42:42 +0400 [thread overview]
Message-ID: <1403602962-18946-1-git-send-email-vdavydov@parallels.com> (raw)
In-Reply-To: <20140624075011.GD4836@js1304-P5Q-DELUXE>
SLUB's implementation of kmem_cache_shrink skips nodes that have
nr_partial=0, because they surely don't have any empty slabs to free.
This check is done w/o holding any locks, therefore it can race with
concurrent kfree adding an empty slab to a partial list. As a result, a
just shrinked cache can have empty slabs.
This is unacceptable for kmemcg, which needs to be sure that there will
be no empty slabs on dead memcg caches after kmem_cache_shrink was
called, because otherwise we may leak a dead cache.
Let's fix this race by checking if node partial list is empty under
node->list_lock. Since the nr_partial!=0 branch of kmem_cache_shrink
does nothing if the list is empty, we can simply remove the nr_partial=0
check.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Reported-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
---
mm/slub.c | 3 ---
1 file changed, 3 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c
index 67da14d9ec70..891ac6cd78cc 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3397,9 +3397,6 @@ int __kmem_cache_shrink(struct kmem_cache *s)
flush_all(s);
for_each_kmem_cache_node(s, node, n) {
- if (!n->nr_partial)
- continue;
-
for (i = 0; i < objects; i++)
INIT_LIST_HEAD(slabs_by_inuse + i);
--
1.7.10.4
next prev parent reply other threads:[~2014-06-24 9:43 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-12 20:38 [PATCH -mm v3 0/8] memcg/slab: reintroduce dead cache self-destruction Vladimir Davydov
2014-06-12 20:38 ` [PATCH -mm v3 1/8] memcg: cleanup memcg_cache_params refcnt usage Vladimir Davydov
2014-06-12 20:38 ` [PATCH -mm v3 2/8] memcg: destroy kmem caches when last slab is freed Vladimir Davydov
2014-06-12 20:38 ` [PATCH -mm v3 3/8] memcg: mark caches that belong to offline memcgs as dead Vladimir Davydov
2014-06-12 20:38 ` [PATCH -mm v3 4/8] slub: don't fail kmem_cache_shrink if slab placement optimization fails Vladimir Davydov
2014-06-12 20:38 ` [PATCH -mm v3 5/8] slub: make slab_free non-preemptable Vladimir Davydov
2014-06-12 20:38 ` [PATCH -mm v3 6/8] memcg: wait for kfree's to finish before destroying cache Vladimir Davydov
2014-06-12 20:38 ` [PATCH -mm v3 7/8] slub: make dead memcg caches discard free slabs immediately Vladimir Davydov
2014-06-13 16:54 ` Christoph Lameter
2014-06-24 7:50 ` Joonsoo Kim
2014-06-24 8:25 ` Vladimir Davydov
2014-06-24 9:42 ` Vladimir Davydov [this message]
2014-06-12 20:38 ` [PATCH -mm v3 8/8] slab: do not keep free objects/slabs on dead memcg caches Vladimir Davydov
2014-06-12 20:41 ` Vladimir Davydov
2014-06-24 7:25 ` Joonsoo Kim
2014-06-24 7:42 ` Vladimir Davydov
2014-06-24 12:28 ` [PATCH -mm] slab: set free_limit for dead caches to 0 Vladimir Davydov
2014-06-24 7:38 ` [PATCH -mm v3 8/8] slab: do not keep free objects/slabs on dead memcg caches Joonsoo Kim
2014-06-24 7:48 ` Vladimir Davydov
2014-06-25 13:45 ` Vladimir Davydov
2014-06-27 6:05 ` Joonsoo Kim
2014-06-30 15:49 ` Christoph Lameter
2014-07-01 7:46 ` Vladimir Davydov
2014-06-25 14:39 ` [PATCH] slab: document why cache can have no per cpu array on kfree Vladimir Davydov
2014-06-25 16:19 ` Christoph Lameter
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