[PATCHv8] mm: slab: free kmem_cache_node after destroy sysfs file
From: Dmitry Safonov
Date: Mon Feb 08 2016 - 04:32:14 EST
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 and
cpu_cache/cpu_slub 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 __kmem_cache_release from __kmem_cache_shutdown which now
called on slab_kmem_cache_release (after the last reference to sysfs
file object has dropped).
Reintroduced locking in free_partial as sysfs file might access cache's
partial list after shutdowning - partiall revert of the
commit 69cb8e6b7c2982 ("slub: free slabs without holding locks")
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Suggested-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Signed-off-by: Dmitry Safonov <dsafonov@xxxxxxxxxxxxx>
---
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
v7: by Vladimir's suggestion renamed __kmem_cache_{free_nodes,_release}
and put inside per-cpu freeing of cpu_slub, cpu_cache,
renamed kmem_cache_close to __kmem_cache_release as it's inline functon
v8: reintroduce locking in free_partial & nits from Vladimir
mm/slab.c | 12 ++++++------
mm/slab.h | 1 +
mm/slab_common.c | 1 +
mm/slob.c | 4 ++++
mm/slub.c | 26 ++++++++++++++------------
5 files changed, 26 insertions(+), 18 deletions(-)
diff --git a/mm/slab.c b/mm/slab.c
index 6ecc697..621fbcb 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2275,7 +2275,7 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
err = setup_cpu_cache(cachep, gfp);
if (err) {
- __kmem_cache_shutdown(cachep);
+ __kmem_cache_release(cachep);
return err;
}
@@ -2414,12 +2414,13 @@ int __kmem_cache_shrink(struct kmem_cache *cachep, bool deactivate)
int __kmem_cache_shutdown(struct kmem_cache *cachep)
{
+ return __kmem_cache_shrink(cachep, false);
+}
+
+void __kmem_cache_release(struct kmem_cache *cachep)
+{
int i;
struct kmem_cache_node *n;
- int rc = __kmem_cache_shrink(cachep, false);
-
- if (rc)
- return rc;
free_percpu(cachep->cpu_cache);
@@ -2430,7 +2431,6 @@ 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..2eedace 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_release(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..065b7bd 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_release(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..5ec1580 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_release(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..8a47d96 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3184,6 +3184,12 @@ static void free_kmem_cache_nodes(struct kmem_cache *s)
}
}
+void __kmem_cache_release(struct kmem_cache *s)
+{
+ free_percpu(s->cpu_slab);
+ free_kmem_cache_nodes(s);
+}
+
static int init_kmem_cache_nodes(struct kmem_cache *s)
{
int node;
@@ -3443,28 +3449,31 @@ static void list_slab_objects(struct kmem_cache *s, struct page *page,
/*
* Attempt to free all partial slabs on a node.
- * This is called from kmem_cache_close(). We must be the last thread
- * using the cache and therefore we do not need to lock anymore.
+ * This is called from __kmem_cache_shutdown(). We must take list_lock
+ * because sysfs file might still access partial list after the shutdowning.
*/
static void free_partial(struct kmem_cache *s, struct kmem_cache_node *n)
{
+ unsigned long flags;
struct page *page, *h;
+ spin_lock_irqsave(&n->list_lock, flags);
list_for_each_entry_safe(page, h, &n->partial, lru) {
if (!page->inuse) {
__remove_partial(n, page);
discard_slab(s, page);
} else {
list_slab_objects(s, page,
- "Objects remaining in %s on kmem_cache_close()");
+ "Objects remaining in %s on __kmem_cache_shutdown()");
}
}
+ spin_unlock_irqrestore(&n->list_lock, flags);
}
/*
* Release all resources used by a slab cache.
*/
-static inline int kmem_cache_close(struct kmem_cache *s)
+int __kmem_cache_shutdown(struct kmem_cache *s)
{
int node;
struct kmem_cache_node *n;
@@ -3476,16 +3485,9 @@ static inline int kmem_cache_close(struct kmem_cache *s)
if (n->nr_partial || slabs_node(s, node))
return 1;
}
- free_percpu(s->cpu_slab);
- free_kmem_cache_nodes(s);
return 0;
}
-int __kmem_cache_shutdown(struct kmem_cache *s)
-{
- return kmem_cache_close(s);
-}
-
/********************************************************************
* Kmalloc subsystem
*******************************************************************/
@@ -3980,7 +3982,7 @@ int __kmem_cache_create(struct kmem_cache *s, unsigned long flags)
memcg_propagate_slab_attrs(s);
err = sysfs_slab_add(s);
if (err)
- kmem_cache_close(s);
+ __kmem_cache_release(s);
return err;
}
--
2.7.0