linux-kernel - [PATCH] mm, slab: memcg_link the SLAB's kmem

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Message-Id: <20180319210020.60289-1-shakeelb@google.com>
Date:   Mon, 19 Mar 2018 14:00:20 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Tejun Heo <tj@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Greg Thelen <gthelen@...gle.com>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Shakeel Butt <shakeelb@...gle.com>
Subject: [PATCH] mm, slab: memcg_link the SLAB's kmem_cache

All the root caches are linked into slab_root_caches which was
introduced by the commit 510ded33e075 ("slab: implement slab_root_caches
list") but it missed to add the SLAB's kmem_cache.

While experimenting with opt-in/opt-out kmem accounting, I noticed
system crashes due to NULL dereference inside cache_from_memcg_idx()
while deferencing kmem_cache.memcg_params.memcg_caches. The upstream
clean kernel will not see these crashes but SLAB should be consistent
with SLUB which does linked its boot caches (kmem_cache_node and
kmem_cache) into slab_root_caches.

Fixes: 510ded33e075c ("slab: implement slab_root_caches list")
Signed-off-by: Shakeel Butt <shakeelb@...gle.com>
---
 mm/slab.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/slab.c b/mm/slab.c
index 324446621b3e..9095c3945425 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1283,6 +1283,7 @@ void __init kmem_cache_init(void)
 				  nr_node_ids * sizeof(struct kmem_cache_node *),
 				  SLAB_HWCACHE_ALIGN, 0, 0);
 	list_add(&kmem_cache->list, &slab_caches);
+	memcg_link_cache(kmem_cache);
 	slab_state = PARTIAL;

 	/*
-- 
2.16.2.804.g6dcf76e118-goog