[PATCHv6] mm: slab: free kmem_cache_node after destroy sysfs file

Dmitry Safonov
2016-02-05T15:45:51Z

With enabled slub_debug alloc_calls_show will try to track location and
user of slab object on each online node, kmem_cache_node structure
shouldn't be freed till there is the last reference to sysfs file.

Fixes the following panic:
[43963.463055] BUG: unable to handle kernel
[43963.463090] NULL pointer dereference at 0000000000000020
[43963.463146] IP: [<ffffffff811c6959>] list_locations+0x169/0x4e0
[43963.463185] PGD 257304067 PUD 438456067 PMD 0
[43963.463220] Oops: 0000 [#1] SMP
[43963.463850] CPU: 3 PID: 973074 Comm: cat ve: 0 Not tainted 3.10.0-229.7.2.ovz.9.30-00007-japdoll-dirty #2 9.30
[43963.463913] Hardware name: DEPO Computers To Be Filled By O.E.M./H67DE3, BIOS L1.60c 07/14/2011
[43963.463976] task: ffff88042a5dc5b0 ti: ffff88037f8d8000 task.ti: ffff88037f8d8000
[43963.464036] RIP: 0010:[<ffffffff811c6959>] [<ffffffff811c6959>] list_locations+0x169/0x4e0
[43963.464725] Call Trace:
[43963.464756] [<ffffffff811c6d1d>] alloc_calls_show+0x1d/0x30
[43963.464793] [<ffffffff811c15ab>] slab_attr_show+0x1b/0x30
[43963.464829] [<ffffffff8125d27a>] sysfs_read_file+0x9a/0x1a0
[43963.464865] [<ffffffff811e3c6c>] vfs_read+0x9c/0x170
[43963.464900] [<ffffffff811e4798>] SyS_read+0x58/0xb0
[43963.464936] [<ffffffff81612d49>] system_call_fastpath+0x16/0x1b
[43963.464970] Code: 5e 07 12 00 b9 00 04 00 00 3d 00 04 00 00 0f 4f c1 3d 00 04 00 00 89 45 b0 0f 84 c3 00 00 00 48 63 45 b0 49 8b 9c c4 f8 00 00 00 <48> 8b 43 20 48 85 c0 74 b6 48 89 df e8 46 37 44 00 48 8b 53 10
[43963.465119] RIP [<ffffffff811c6959>] list_locations+0x169/0x4e0
[43963.465155] RSP <ffff88037f8dbe28>
[43963.465185] CR2: 0000000000000020

Separated nodes structures freeing into __kmem_cache_free_nodes and use
it at kmem_cache_release.

Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
---
v2: Down with SLAB_SUPPORTS_SYSFS thing.
v3: Moved sysfs_slab_remove inside shutdown_cache
v4: Reworked all to shutdown & free caches on object->release()
v5: Made separate __kmem_cache_free_nodes function and call it on release.
v6: Fixed silly error: call to __kmem_cache_free_nodes from kmem_cache_close

mm/slab.c | 12 +++++++++---
mm/slab.h | 1 +
mm/slab_common.c | 1 +
mm/slob.c | 4 ++++
mm/slub.c | 7 +++----
5 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index 6ecc697..3ccdf3c 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2276,6 +2276,7 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
err = setup_cpu_cache(cachep, gfp);
if (err) {
__kmem_cache_shutdown(cachep);
+ __kmem_cache_free_nodes(cachep);
return err;
}

@@ -2414,8 +2415,6 @@ int __kmem_cache_shrink(struct kmem_cache *cachep, bool deactivate)

int __kmem_cache_shutdown(struct kmem_cache *cachep)
{
- int i;
- struct kmem_cache_node *n;
int rc = __kmem_cache_shrink(cachep, false);

if (rc)
@@ -2423,6 +2422,14 @@ int __kmem_cache_shutdown(struct kmem_cache *cachep)

free_percpu(cachep->cpu_cache);

+ return 0;
+}
+
+void __kmem_cache_free_nodes(struct kmem_cache *cachep)
+{
+ int i;
+ struct kmem_cache_node *n;
+
/* NUMA: free the node structures */
for_each_kmem_cache_node(cachep, i, n) {
kfree(n->shared);
@@ -2430,7 +2437,6 @@ int __kmem_cache_shutdown(struct kmem_cache *cachep)
kfree(n);
cachep->node[i] = NULL;
}
- return 0;
}

/*
diff --git a/mm/slab.h b/mm/slab.h
index 834ad24..b1a6576 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -140,6 +140,7 @@ static inline unsigned long kmem_cache_flags(unsigned long object_size,
#define CACHE_CREATE_MASK (SLAB_CORE_FLAGS | SLAB_DEBUG_FLAGS | SLAB_CACHE_FLAGS)

int __kmem_cache_shutdown(struct kmem_cache *);
+void __kmem_cache_free_nodes(struct kmem_cache *);
int __kmem_cache_shrink(struct kmem_cache *, bool);
void slab_kmem_cache_release(struct kmem_cache *);

diff --git a/mm/slab_common.c b/mm/slab_common.c
index b50aef0..0bc2da3 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -693,6 +693,7 @@ static inline int shutdown_memcg_caches(struct kmem_cache *s,

void slab_kmem_cache_release(struct kmem_cache *s)
{
+ __kmem_cache_free_nodes(s);
destroy_memcg_params(s);
kfree_const(s->name);
kmem_cache_free(kmem_cache, s);
diff --git a/mm/slob.c b/mm/slob.c
index 17e8f8c..242d77d 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -630,6 +630,10 @@ int __kmem_cache_shutdown(struct kmem_cache *c)
return 0;
}

+void __kmem_cache_free_nodes(struct kmem_cache *c)
+{
+}
+
int __kmem_cache_shrink(struct kmem_cache *d, bool deactivate)
{
return 0;
diff --git a/mm/slub.c b/mm/slub.c
index 2e1355a..b177cdb 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3173,7 +3173,7 @@ static void early_kmem_cache_node_alloc(int node)
__add_partial(n, page, DEACTIVATE_TO_HEAD);
}

-static void free_kmem_cache_nodes(struct kmem_cache *s)
+void __kmem_cache_free_nodes(struct kmem_cache *s)
{
int node;
struct kmem_cache_node *n;
@@ -3199,7 +3199,7 @@ static int init_kmem_cache_nodes(struct kmem_cache *s)
GFP_KERNEL, node);

if (!n) {
- free_kmem_cache_nodes(s);
+ __kmem_cache_free_nodes(s);
return 0;
}

@@ -3405,7 +3405,7 @@ static int kmem_cache_open(struct kmem_cache *s, unsigned long flags)
if (alloc_kmem_cache_cpus(s))
return 0;

- free_kmem_cache_nodes(s);
+ __kmem_cache_free_nodes(s);
error:
if (flags & SLAB_PANIC)
panic("Cannot create slab %s size=%lu realsize=%u "
@@ -3477,7 +3477,6 @@ static inline int kmem_cache_close(struct kmem_cache *s)
return 1;
}
free_percpu(s->cpu_slab);
- free_kmem_cache_nodes(s);
return 0;
}

--
2.7.0