slub: use sysfs'es release mechanism for kmem_cache

debugobjects warning during netfilter exit:

    ------------[ cut here ]------------
    WARNING: CPU: 6 PID: 4178 at lib/debugobjects.c:260 debug_print_object+0x8d/0xb0()
    ODEBUG: free active (active state 0) object type: timer_list hint: delayed_work_timer_fn+0x0/0x20
    Modules linked in:
    CPU: 6 PID: 4178 Comm: kworker/u16:2 Tainted: G        W 3.11.0-next-20130906-sasha #3984
    Workqueue: netns cleanup_net
    Call Trace:
      dump_stack+0x52/0x87
      warn_slowpath_common+0x8c/0xc0
      warn_slowpath_fmt+0x46/0x50
      debug_print_object+0x8d/0xb0
      __debug_check_no_obj_freed+0xa5/0x220
      debug_check_no_obj_freed+0x15/0x20
      kmem_cache_free+0x197/0x340
      kmem_cache_destroy+0x86/0xe0
      nf_conntrack_cleanup_net_list+0x131/0x170
      nf_conntrack_pernet_exit+0x5d/0x70
      ops_exit_list+0x5e/0x70
      cleanup_net+0xfb/0x1c0
      process_one_work+0x338/0x550
      worker_thread+0x215/0x350
      kthread+0xe7/0xf0
      ret_from_fork+0x7c/0xb0

Also during dcookie cleanup:

    WARNING: CPU: 12 PID: 9725 at lib/debugobjects.c:260 debug_print_object+0x8c/0xb0()
    ODEBUG: free active (active state 0) object type: timer_list hint: delayed_work_timer_fn+0x0/0x20
    Modules linked in:
    CPU: 12 PID: 9725 Comm: trinity-c141 Not tainted 3.15.0-rc2-next-20140423-sasha-00018-gc4ff6c4 #408
    Call Trace:
      dump_stack (lib/dump_stack.c:52)
      warn_slowpath_common (kernel/panic.c:430)
      warn_slowpath_fmt (kernel/panic.c:445)
      debug_print_object (lib/debugobjects.c:262)
      __debug_check_no_obj_freed (lib/debugobjects.c:697)
      debug_check_no_obj_freed (lib/debugobjects.c:726)
      kmem_cache_free (mm/slub.c:2689 mm/slub.c:2717)
      kmem_cache_destroy (mm/slab_common.c:363)
      dcookie_unregister (fs/dcookies.c:302 fs/dcookies.c:343)
      event_buffer_release (arch/x86/oprofile/../../../drivers/oprofile/event_buffer.c:153)
      __fput (fs/file_table.c:217)
      ____fput (fs/file_table.c:253)
      task_work_run (kernel/task_work.c:125 (discriminator 1))
      do_notify_resume (include/linux/tracehook.h:196 arch/x86/kernel/signal.c:751)
      int_signal (arch/x86/kernel/entry_64.S:807)

Sysfs has a release mechanism.  Use that to release the kmem_cache
structure if CONFIG_SYSFS is enabled.

Only slub is changed - slab currently only supports /proc/slabinfo and
not /sys/kernel/slab/*.  We talked about adding that and someone was
working on it.

[[email protected]: fix CONFIG_SYSFS=n build]
[[email protected]: fix CONFIG_SYSFS=n build even more]
Signed-off-by: Christoph Lameter <[email protected]>
Reported-by: Sasha Levin <[email protected]>
Tested-by: Sasha Levin <[email protected]>
Acked-by: Greg KH <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: Russell King <[email protected]>
Cc: Bart Van Assche <[email protected]>
Cc: Al Viro <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: Christoph Lameter

include/linux/slub_def.h

@@ -101,4 +101,13 @@ struct kmem_cache {
 	struct kmem_cache_node *node[MAX_NUMNODES];
 };
 
+#ifdef CONFIG_SYSFS
+#define SLAB_SUPPORTS_SYSFS
+void sysfs_slab_remove(struct kmem_cache *);
+#else
+static inline void sysfs_slab_remove(struct kmem_cache *s)
+{
+}
+#endif
+
 #endif /* _LINUX_SLUB_DEF_H */

mm/slab.h

@@ -91,6 +91,7 @@ __kmem_cache_alias(const char *name, size_t size, size_t align,
 #define CACHE_CREATE_MASK (SLAB_CORE_FLAGS | SLAB_DEBUG_FLAGS | SLAB_CACHE_FLAGS)
 
 int __kmem_cache_shutdown(struct kmem_cache *);
+void slab_kmem_cache_release(struct kmem_cache *);
 
 struct seq_file;
 struct file;

mm/slab_common.c

@@ -323,6 +323,12 @@ static int kmem_cache_destroy_memcg_children(struct kmem_cache *s)
 }
 #endif /* CONFIG_MEMCG_KMEM */
 
+void slab_kmem_cache_release(struct kmem_cache *s)
+{
+	kfree(s->name);
+	kmem_cache_free(kmem_cache, s);
+}
+
 void kmem_cache_destroy(struct kmem_cache *s)
 {
 	get_online_cpus();
@@ -352,8 +358,11 @@ void kmem_cache_destroy(struct kmem_cache *s)
 		rcu_barrier();
 
 	memcg_free_cache_params(s);
-	kfree(s->name);
-	kmem_cache_free(kmem_cache, s);
+#ifdef SLAB_SUPPORTS_SYSFS
+	sysfs_slab_remove(s);
+#else
+	slab_kmem_cache_release(s);
+#endif
 	goto out_put_cpus;
 
 out_unlock:

mm/slub.c

@@ -210,14 +210,11 @@ enum track_item { TRACK_ALLOC, TRACK_FREE };
 #ifdef CONFIG_SYSFS
 static int sysfs_slab_add(struct kmem_cache *);
 static int sysfs_slab_alias(struct kmem_cache *, const char *);
-static void sysfs_slab_remove(struct kmem_cache *);
 static void memcg_propagate_slab_attrs(struct kmem_cache *s);
 #else
 static inline int sysfs_slab_add(struct kmem_cache *s) { return 0; }
 static inline int sysfs_slab_alias(struct kmem_cache *s, const char *p)
 							{ return 0; }
-static inline void sysfs_slab_remove(struct kmem_cache *s) { }
-
 static inline void memcg_propagate_slab_attrs(struct kmem_cache *s) { }
 #endif
 
@@ -3238,24 +3235,7 @@ static inline int kmem_cache_close(struct kmem_cache *s)
 
 int __kmem_cache_shutdown(struct kmem_cache *s)
 {
-	int rc = kmem_cache_close(s);
-
-	if (!rc) {
-		/*
-		 * Since slab_attr_store may take the slab_mutex, we should
-		 * release the lock while removing the sysfs entry in order to
-		 * avoid a deadlock. Because this is pretty much the last
-		 * operation we do and the lock will be released shortly after
-		 * that in slab_common.c, we could just move sysfs_slab_remove
-		 * to a later point in common code. We should do that when we
-		 * have a common sysfs framework for all allocators.
-		 */
-		mutex_unlock(&slab_mutex);
-		sysfs_slab_remove(s);
-		mutex_lock(&slab_mutex);
-	}
-
-	return rc;
+	return kmem_cache_close(s);
 }
 
 /********************************************************************
@@ -5122,13 +5102,19 @@ static void memcg_propagate_slab_attrs(struct kmem_cache *s)
 #endif
 }
 
+static void kmem_cache_release(struct kobject *k)
+{
+	slab_kmem_cache_release(to_slab(k));
+}
+
 static const struct sysfs_ops slab_sysfs_ops = {
 	.show = slab_attr_show,
 	.store = slab_attr_store,
 };
 
 static struct kobj_type slab_ktype = {
 	.sysfs_ops = &slab_sysfs_ops,
+	.release = kmem_cache_release,
 };
 
 static int uevent_filter(struct kset *kset, struct kobject *kobj)
@@ -5255,7 +5241,7 @@ static int sysfs_slab_add(struct kmem_cache *s)
 	goto out;
 }
 
-static void sysfs_slab_remove(struct kmem_cache *s)
+void sysfs_slab_remove(struct kmem_cache *s)
 {
 	if (slab_state < FULL)
 		/*