[RFC 5/5] dma-buf/sync_file: rework fence storage in struct file

[Gustavo Padovan <gustavo@padovan.org>]

From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>

Create sync_file->fence to abstract the type of fence we are using for
each sync_file. If only one fence is present we use a normal struct fence
but if there is more fences to be added to the sync_file a fence_array
is created.

This behaviour is transparent all sync_file functions, but
sync_file_set_fence() which sets the fence in the sync_file_merge(). It
is this functions that decides to use a fence or fence_array based on
num_fences.

This change cleans up sync_file a bit. We don't need to have sync_file_cb
array anymore. Instead, as we always have  one fence, only one fence
callback is registered per sync_file.

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
---
 drivers/dma-buf/sync_file.c          | 129 +++++++++++++++++++++++++----------
 drivers/staging/android/sync_debug.c |   5 +-
 include/linux/sync_file.h            |  12 ++--
 3 files changed, 100 insertions(+), 46 deletions(-)

diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c
index 9aaa608..5044ef2 100644
--- a/drivers/dma-buf/sync_file.c
+++ b/drivers/dma-buf/sync_file.c
@@ -25,14 +25,15 @@
 #include <linux/anon_inodes.h>
 #include <linux/sync_file.h>
 #include <uapi/linux/sync_file.h>
+#include <linux/fence-array.h>
 
 static const struct file_operations sync_file_fops;
 
-static struct sync_file *sync_file_alloc(int size)
+static struct sync_file *sync_file_alloc(void)
 {
 	struct sync_file *sync_file;
 
-	sync_file = kzalloc(size, GFP_KERNEL);
+	sync_file = kzalloc(sizeof(*sync_file), GFP_KERNEL);
 	if (!sync_file)
 		return NULL;
 
@@ -45,6 +46,8 @@ static struct sync_file *sync_file_alloc(int size)
 
 	init_waitqueue_head(&sync_file->wq);
 
+	INIT_LIST_HEAD(&sync_file->cb.node);
+
 	return sync_file;
 
 err:
@@ -54,11 +57,9 @@ err:
 
 static void fence_check_cb_func(struct fence *f, struct fence_cb *cb)
 {
-	struct sync_file_cb *check;
 	struct sync_file *sync_file;
 
-	check = container_of(cb, struct sync_file_cb, cb);
-	sync_file = check->sync_file;
+	sync_file = container_of(cb, struct sync_file, cb);
 
 	if (atomic_dec_and_test(&sync_file->status))
 		wake_up_all(&sync_file->wq);
@@ -76,21 +77,20 @@ struct sync_file *sync_file_create(struct fence *fence)
 {
 	struct sync_file *sync_file;
 
-	sync_file = sync_file_alloc(offsetof(struct sync_file, cbs[1]));
+	sync_file = sync_file_alloc();
 	if (!sync_file)
 		return NULL;
 
+	sync_file->fence = fence;
 	sync_file->num_fences = 1;
+
 	atomic_set(&sync_file->status, 1);
 	snprintf(sync_file->name, sizeof(sync_file->name), "%s-%s%llu-%d",
 		 fence->ops->get_driver_name(fence),
 		 fence->ops->get_timeline_name(fence), fence->context,
 		 fence->seqno);
 
-	sync_file->cbs[0].fence = fence;
-	sync_file->cbs[0].sync_file = sync_file;
-	if (fence_add_callback(fence, &sync_file->cbs[0].cb,
-			       fence_check_cb_func))
+	if (fence_add_callback(fence, &sync_file->cb, fence_check_cb_func))
 		atomic_dec(&sync_file->status);
 
 	return sync_file;
@@ -121,14 +121,31 @@ err:
 	return NULL;
 }
 
-static void sync_file_add_pt(struct sync_file *sync_file, int *i,
+static int sync_file_set_fence(struct sync_file *sync_file,
+			       struct fence **fences)
+{
+	struct fence_array *array;
+
+	if (sync_file->num_fences == 1) {
+		sync_file->fence = fences[0];
+	} else {
+		array = fence_array_create(sync_file->num_fences, fences,
+					   fence_context_alloc(1), 1, false);
+		if (!array)
+			return -ENOMEM;
+
+		sync_file->fence = &array->base;
+	}
+
+	return 0;
+}
+
+static void fences_add_fence(struct fence **fences, int *i,
 			     struct fence *fence)
 {
-	sync_file->cbs[*i].fence = fence;
-	sync_file->cbs[*i].sync_file = sync_file;
+	fences[*i] = fence;
 
-	if (!fence_add_callback(fence, &sync_file->cbs[*i].cb,
-				fence_check_cb_func)) {
+	if (!fence_is_signaled(fence)) {
 		fence_get(fence);
 		(*i)++;
 	}
@@ -149,14 +166,31 @@ static struct sync_file *sync_file_merge(const char *name, struct sync_file *a,
 {
 	int num_fences = a->num_fences + b->num_fences;
 	struct sync_file *sync_file;
+	struct fence **fences, **a_fences, **b_fences;
 	int i, i_a, i_b;
-	unsigned long size = offsetof(struct sync_file, cbs[num_fences]);
 
-	sync_file = sync_file_alloc(size);
+	sync_file = sync_file_alloc();
 	if (!sync_file)
 		return NULL;
 
-	atomic_set(&sync_file->status, num_fences);
+	fences = kcalloc(num_fences, sizeof(**fences), GFP_KERNEL);
+	if (!fences)
+		goto err;
+
+	atomic_set(&sync_file->status, 1);
+
+	a_fences = fence_get_fences(a->fence);
+	if (!a_fences) {
+		kfree(fences);
+		goto err;
+	}
+
+	b_fences = fence_get_fences(b->fence);
+	if (!b_fences) {
+		kfree(a_fences);
+		kfree(fences);
+		goto err;
+	}
 
 	/*
 	 * Assume sync_file a and b are both ordered and have no
@@ -166,22 +200,22 @@ static struct sync_file *sync_file_merge(const char *name, struct sync_file *a,
 	 * and sync_file_create, this is a reasonable assumption.
 	 */
 	for (i = i_a = i_b = 0; i_a < a->num_fences && i_b < b->num_fences; ) {
-		struct fence *pt_a = a->cbs[i_a].fence;
-		struct fence *pt_b = b->cbs[i_b].fence;
+		struct fence *pt_a = a_fences[i_a];
+		struct fence *pt_b = b_fences[i_b];
 
 		if (pt_a->context < pt_b->context) {
-			sync_file_add_pt(sync_file, &i, pt_a);
+			fences_add_fence(fences, &i, pt_a);
 
 			i_a++;
 		} else if (pt_a->context > pt_b->context) {
-			sync_file_add_pt(sync_file, &i, pt_b);
+			fences_add_fence(fences, &i, pt_b);
 
 			i_b++;
 		} else {
 			if (pt_a->seqno - pt_b->seqno <= INT_MAX)
-				sync_file_add_pt(sync_file, &i, pt_a);
+				fences_add_fence(fences, &i, pt_a);
 			else
-				sync_file_add_pt(sync_file, &i, pt_b);
+				fences_add_fence(fences, &i, pt_b);
 
 			i_a++;
 			i_b++;
@@ -189,31 +223,49 @@ static struct sync_file *sync_file_merge(const char *name, struct sync_file *a,
 	}
 
 	for (; i_a < a->num_fences; i_a++)
-		sync_file_add_pt(sync_file, &i, a->cbs[i_a].fence);
+		fences_add_fence(fences, &i, a_fences[i_a]);
 
 	for (; i_b < b->num_fences; i_b++)
-		sync_file_add_pt(sync_file, &i, b->cbs[i_b].fence);
+		fences_add_fence(fences, &i, b_fences[i_b]);
 
-	if (num_fences > i)
-		atomic_sub(num_fences - i, &sync_file->status);
+	if (num_fences > i) {
+		fences = krealloc(fences, i * sizeof(**fences),
+				  GFP_KERNEL);
+		if (!fences)
+			goto ab_err;
+	}
 	sync_file->num_fences = i;
 
+	if (sync_file_set_fence(sync_file, fences) < 0) {
+		kfree(fences);
+		goto ab_err;
+	}
+
+	if (fence_add_callback(sync_file->fence, &sync_file->cb,
+			       fence_check_cb_func))
+		atomic_dec(&sync_file->status);
+
 	strlcpy(sync_file->name, name, sizeof(sync_file->name));
 	return sync_file;
+
+ab_err:
+	kfree(a_fences);
+	kfree(b_fences);
+
+err:
+	fput(sync_file->file);
+	return NULL;
+
 }
 
 static void sync_file_free(struct kref *kref)
 {
 	struct sync_file *sync_file = container_of(kref, struct sync_file,
 						     kref);
-	int i;
-
-	for (i = 0; i < sync_file->num_fences; ++i) {
-		fence_remove_callback(sync_file->cbs[i].fence,
-				      &sync_file->cbs[i].cb);
-		fence_put(sync_file->cbs[i].fence);
-	}
 
+	fence_remove_callback(sync_file->fence, &sync_file->cb);
+	fence_teardown(sync_file->fence);
+	fence_put(sync_file->fence);
 	kfree(sync_file);
 }
 
@@ -315,6 +367,7 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
 {
 	struct sync_file_info info;
 	struct sync_fence_info *fence_info = NULL;
+	struct fence **fences;
 	__u32 size;
 	int ret, i;
 
@@ -341,8 +394,10 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
 	if (!fence_info)
 		return -ENOMEM;
 
-	for (i = 0; i < sync_file->num_fences; ++i)
-		sync_fill_fence_info(sync_file->cbs[i].fence, &fence_info[i]);
+	fences = fence_get_fences(sync_file->fence);
+	for (i = 0; i < sync_file->num_fences; i++)
+		sync_fill_fence_info(fences[i], &fence_info[i]);
+	kfree(fences);
 
 	if (copy_to_user(u64_to_user_ptr(info.sync_fence_info), fence_info,
 			 size)) {
diff --git a/drivers/staging/android/sync_debug.c b/drivers/staging/android/sync_debug.c
index 5f57499..5fb6d3d 100644
--- a/drivers/staging/android/sync_debug.c
+++ b/drivers/staging/android/sync_debug.c
@@ -156,13 +156,16 @@ static void sync_print_obj(struct seq_file *s, struct sync_timeline *obj)
 static void sync_print_sync_file(struct seq_file *s,
 				  struct sync_file *sync_file)
 {
+	struct fence **fences;
 	int i;
 
 	seq_printf(s, "[%p] %s: %s\n", sync_file, sync_file->name,
 		   sync_status_str(atomic_read(&sync_file->status)));
 
+	fences = fence_get_fences(sync_file->fence);
 	for (i = 0; i < sync_file->num_fences; ++i)
-		sync_print_fence(s, sync_file->cbs[i].fence, true);
+		sync_print_fence(s, fences[i], true);
+	kfree(fences);
 }
 
 static int sync_debugfs_show(struct seq_file *s, void *unused)
diff --git a/include/linux/sync_file.h b/include/linux/sync_file.h
index c6ffe8b..d13885f 100644
--- a/include/linux/sync_file.h
+++ b/include/linux/sync_file.h
@@ -20,12 +20,6 @@
 #include <linux/spinlock.h>
 #include <linux/fence.h>
 
-struct sync_file_cb {
-	struct fence_cb cb;
-	struct fence *fence;
-	struct sync_file *sync_file;
-};
-
 /**
  * struct sync_file - sync file to export to the userspace
  * @file:		file representing this fence
@@ -35,7 +29,8 @@ struct sync_file_cb {
  * @num_fences:		number of sync_pts in the fence
  * @wq:			wait queue for fence signaling
  * @status:		0: signaled, >0:active, <0: error
- * @cbs:		sync_pts callback information
+ * @fence:		fence with the fences in the sync_file
+ * @cb:			fence callback information
  */
 struct sync_file {
 	struct file		*file;
@@ -49,7 +44,8 @@ struct sync_file {
 	wait_queue_head_t	wq;
 	atomic_t		status;
 
-	struct sync_file_cb	cbs[];
+	struct fence		*fence;
+	struct fence_cb cb;
 };
 
 struct sync_file *sync_file_create(struct fence *fence);
-- 
2.5.5