Merge tag 'slab-for-6.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab

Pull slab fixes from Vlastimil Babka:
 "Fixes for issues introduced in this merge window: kobject memory leak,
  unsupressed warning and possible lockup in new slub_kunit tests,
  misleading code in kvfree_rcu_queue_batch()"

* tag 'slab-for-6.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab:
  slub/kunit: skip test_kfree_rcu when the slub kunit test is built-in
  mm, slab: suppress warnings in test_leak_destroy kunit test
  rcu/kvfree: Refactor kvfree_rcu_queue_batch()
  mm, slab: fix use of SLAB_SUPPORTS_SYSFS in kmem_cache_release()

kernel/rcu/tree.c

@@ -3607,11 +3607,12 @@ kvfree_rcu_queue_batch(struct kfree_rcu_cpu *krcp)
 			}
 
 			// One work is per one batch, so there are three
-			// "free channels", the batch can handle. It can
-			// be that the work is in the pending state when
-			// channels have been detached following by each
-			// other.
+			// "free channels", the batch can handle. Break
+			// the loop since it is done with this CPU thus
+			// queuing an RCU work is _always_ success here.
 			queued = queue_rcu_work(system_unbound_wq, &krwp->rcu_work);
+			WARN_ON_ONCE(!queued);
+			break;
 		}
 	}
 

lib/slub_kunit.c

@@ -164,10 +164,16 @@ struct test_kfree_rcu_struct {
 
 static void test_kfree_rcu(struct kunit *test)
 {
-	struct kmem_cache *s = test_kmem_cache_create("TestSlub_kfree_rcu",
+	struct kmem_cache *s;
+	struct test_kfree_rcu_struct *p;
+
+	if (IS_BUILTIN(CONFIG_SLUB_KUNIT_TEST))
+		kunit_skip(test, "can't do kfree_rcu() when test is built-in");
+
+	s = test_kmem_cache_create("TestSlub_kfree_rcu",
 				   sizeof(struct test_kfree_rcu_struct),
 				   SLAB_NO_MERGE);
-	struct test_kfree_rcu_struct *p = kmem_cache_alloc(s, GFP_KERNEL);
+	p = kmem_cache_alloc(s, GFP_KERNEL);
 
 	kfree_rcu(p, rcu);
 	kmem_cache_destroy(s);
@@ -177,13 +183,13 @@ static void test_kfree_rcu(struct kunit *test)
 
 static void test_leak_destroy(struct kunit *test)
 {
-	struct kmem_cache *s = test_kmem_cache_create("TestSlub_kfree_rcu",
+	struct kmem_cache *s = test_kmem_cache_create("TestSlub_leak_destroy",
 							64, SLAB_NO_MERGE);
 	kmem_cache_alloc(s, GFP_KERNEL);
 
 	kmem_cache_destroy(s);
 
-	KUNIT_EXPECT_EQ(test, 1, slab_errors);
+	KUNIT_EXPECT_EQ(test, 2, slab_errors);
 }
 
 static int test_init(struct kunit *test)

mm/slab.h

@@ -310,7 +310,7 @@ struct kmem_cache {
 };
 
 #if defined(CONFIG_SYSFS) && !defined(CONFIG_SLUB_TINY)
-#define SLAB_SUPPORTS_SYSFS
+#define SLAB_SUPPORTS_SYSFS 1
 void sysfs_slab_unlink(struct kmem_cache *s);
 void sysfs_slab_release(struct kmem_cache *s);
 #else
@@ -546,6 +546,12 @@ static inline bool kmem_cache_debug_flags(struct kmem_cache *s, slab_flags_t fla
 	return false;
 }
 
+#if IS_ENABLED(CONFIG_SLUB_DEBUG) && IS_ENABLED(CONFIG_KUNIT)
+bool slab_in_kunit_test(void);
+#else
+static inline bool slab_in_kunit_test(void) { return false; }
+#endif
+
 #ifdef CONFIG_SLAB_OBJ_EXT
 
 /*

mm/slab_common.c

@@ -508,6 +508,7 @@ void kmem_cache_destroy(struct kmem_cache *s)
 	kasan_cache_shutdown(s);
 
 	err = __kmem_cache_shutdown(s);
+	if (!slab_in_kunit_test())
 		WARN(err, "%s %s: Slab cache still has objects when called from %pS",
 		     __func__, s->name, (void *)_RET_IP_);
 

mm/slub.c

@@ -827,7 +827,7 @@ static bool slab_add_kunit_errors(void)
 	return true;
 }
 
-static bool slab_in_kunit_test(void)
+bool slab_in_kunit_test(void)
 {
 	struct kunit_resource *resource;
 
@@ -843,7 +843,6 @@ static bool slab_in_kunit_test(void)
 }
 #else
 static inline bool slab_add_kunit_errors(void) { return false; }
-static inline bool slab_in_kunit_test(void) { return false; }
 #endif
 
 static inline unsigned int size_from_object(struct kmem_cache *s)
@@ -5436,6 +5435,8 @@ static void list_slab_objects(struct kmem_cache *s, struct slab *slab,
 	for_each_object(p, s, addr, slab->objects) {
 
 		if (!test_bit(__obj_to_index(s, addr, p), object_map)) {
+			if (slab_add_kunit_errors())
+				continue;
 			pr_err("Object 0x%p @offset=%tu\n", p, p - addr);
 			print_tracking(s, p);
 		}