[PATCH 4/5] dma-buf: Stop using SLAB_TYPESAFE_BY_RCU in selftests (v2)

[Jason Ekstrand]

The only real-world user of SLAB_TYPESAFE_BY_RCU was i915 and it doesn't
use that anymore so there's no need to be testing it in selftests.

v2 (Jason Ekstrand):
 - Add an rcu_dereference and NULL check when replacing
   dma_fence_get_rcu_safe

Signed-off-by: Jason Ekstrand <jason at jlekstrand.net>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: Christian König <christian.koenig at amd.com>
Cc: Matthew Auld <matthew.auld at intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
---
 drivers/dma-buf/st-dma-fence-chain.c | 24 ++++-------------------
 drivers/dma-buf/st-dma-fence.c       | 29 +++++++---------------------
 2 files changed, 11 insertions(+), 42 deletions(-)

diff --git a/drivers/dma-buf/st-dma-fence-chain.c b/drivers/dma-buf/st-dma-fence-chain.c
index 9525f7f561194..73010184559fe 100644
--- a/drivers/dma-buf/st-dma-fence-chain.c
+++ b/drivers/dma-buf/st-dma-fence-chain.c
@@ -19,36 +19,27 @@
 
 #define CHAIN_SZ (4 << 10)
 
-static struct kmem_cache *slab_fences;
-
-static inline struct mock_fence {
+struct mock_fence {
 	struct dma_fence base;
 	spinlock_t lock;
-} *to_mock_fence(struct dma_fence *f) {
-	return container_of(f, struct mock_fence, base);
-}
+};
 
 static const char *mock_name(struct dma_fence *f)
 {
 	return "mock";
 }
 
-static void mock_fence_release(struct dma_fence *f)
-{
-	kmem_cache_free(slab_fences, to_mock_fence(f));
-}
-
 static const struct dma_fence_ops mock_ops = {
 	.get_driver_name = mock_name,
 	.get_timeline_name = mock_name,
-	.release = mock_fence_release,
+	.release = dma_fence_free,
 };
 
 static struct dma_fence *mock_fence(void)
 {
 	struct mock_fence *f;
 
-	f = kmem_cache_alloc(slab_fences, GFP_KERNEL);
+	f = kmalloc(sizeof(*f), GFP_KERNEL);
 	if (!f)
 		return NULL;
 
@@ -701,14 +692,7 @@ int dma_fence_chain(void)
 	pr_info("sizeof(dma_fence_chain)=%zu\n",
 		sizeof(struct dma_fence_chain));
 
-	slab_fences = KMEM_CACHE(mock_fence,
-				 SLAB_TYPESAFE_BY_RCU |
-				 SLAB_HWCACHE_ALIGN);
-	if (!slab_fences)
-		return -ENOMEM;
-
 	ret = subtests(tests, NULL);
 
-	kmem_cache_destroy(slab_fences);
 	return ret;
 }
diff --git a/drivers/dma-buf/st-dma-fence.c b/drivers/dma-buf/st-dma-fence.c
index c8a12d7ad71ab..f1b90314a07e4 100644
--- a/drivers/dma-buf/st-dma-fence.c
+++ b/drivers/dma-buf/st-dma-fence.c
@@ -14,25 +14,16 @@
 
 #include "selftest.h"
 
-static struct kmem_cache *slab_fences;
-
-static struct mock_fence {
+struct mock_fence {
 	struct dma_fence base;
 	struct spinlock lock;
-} *to_mock_fence(struct dma_fence *f) {
-	return container_of(f, struct mock_fence, base);
-}
+};
 
 static const char *mock_name(struct dma_fence *f)
 {
 	return "mock";
 }
 
-static void mock_fence_release(struct dma_fence *f)
-{
-	kmem_cache_free(slab_fences, to_mock_fence(f));
-}
-
 struct wait_cb {
 	struct dma_fence_cb cb;
 	struct task_struct *task;
@@ -77,14 +68,14 @@ static const struct dma_fence_ops mock_ops = {
 	.get_driver_name = mock_name,
 	.get_timeline_name = mock_name,
 	.wait = mock_wait,
-	.release = mock_fence_release,
+	.release = dma_fence_free,
 };
 
 static struct dma_fence *mock_fence(void)
 {
 	struct mock_fence *f;
 
-	f = kmem_cache_alloc(slab_fences, GFP_KERNEL);
+	f = kmalloc(sizeof(*f), GFP_KERNEL);
 	if (!f)
 		return NULL;
 
@@ -463,7 +454,9 @@ static int thread_signal_callback(void *arg)
 
 		rcu_read_lock();
 		do {
-			f2 = dma_fence_get_rcu_safe(&t->fences[!t->id]);
+			f2 = rcu_dereference(t->fences[!t->id]);
+			if (f2)
+				f2 = dma_fence_get_rcu(f2);
 		} while (!f2 && !kthread_should_stop());
 		rcu_read_unlock();
 
@@ -563,15 +556,7 @@ int dma_fence(void)
 
 	pr_info("sizeof(dma_fence)=%zu\n", sizeof(struct dma_fence));
 
-	slab_fences = KMEM_CACHE(mock_fence,
-				 SLAB_TYPESAFE_BY_RCU |
-				 SLAB_HWCACHE_ALIGN);
-	if (!slab_fences)
-		return -ENOMEM;
-
 	ret = subtests(tests, NULL);
 
-	kmem_cache_destroy(slab_fences);
-
 	return ret;
 }
-- 
2.31.1