staging: android: ion: Remove unused rbtree for ion_buffer

ion_buffer_add() insert ion_buffer into rbtree every time creating
an ion_buffer but never use it after ION reworking.
Also, buffer_lock protects only rbtree operation, remove it together.

Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: YJ Chiang <yj.chiang@mediatek.com>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Acked-by: Laura Abbott <labbott@redhat.com>
Link: https://lore.kernel.org/r/20190712084717.12441-1-lecopzer.chen@mediatek.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/android/ion/ion.c

@@ -29,32 +29,6 @@
 static struct ion_device *internal_dev;
 static int heap_id;
 
-/* this function should only be called while dev->lock is held */
-static void ion_buffer_add(struct ion_device *dev,
-			   struct ion_buffer *buffer)
-{
-	struct rb_node **p = &dev->buffers.rb_node;
-	struct rb_node *parent = NULL;
-	struct ion_buffer *entry;
-
-	while (*p) {
-		parent = *p;
-		entry = rb_entry(parent, struct ion_buffer, node);
-
-		if (buffer < entry) {
-			p = &(*p)->rb_left;
-		} else if (buffer > entry) {
-			p = &(*p)->rb_right;
-		} else {
-			pr_err("%s: buffer already found.", __func__);
-			BUG();
-		}
-	}
-
-	rb_link_node(&buffer->node, parent, p);
-	rb_insert_color(&buffer->node, &dev->buffers);
-}
-
 /* this function should only be called while dev->lock is held */
 static struct ion_buffer *ion_buffer_create(struct ion_heap *heap,
 					    struct ion_device *dev,
@@ -100,9 +74,6 @@ static struct ion_buffer *ion_buffer_create(struct ion_heap *heap,
 
 	INIT_LIST_HEAD(&buffer->attachments);
 	mutex_init(&buffer->lock);
-	mutex_lock(&dev->buffer_lock);
-	ion_buffer_add(dev, buffer);
-	mutex_unlock(&dev->buffer_lock);
 	return buffer;
 
 err1:
@@ -131,11 +102,6 @@ void ion_buffer_destroy(struct ion_buffer *buffer)
 static void _ion_buffer_destroy(struct ion_buffer *buffer)
 {
 	struct ion_heap *heap = buffer->heap;
-	struct ion_device *dev = buffer->dev;
-
-	mutex_lock(&dev->buffer_lock);
-	rb_erase(&buffer->node, &dev->buffers);
-	mutex_unlock(&dev->buffer_lock);
 
 	if (heap->flags & ION_HEAP_FLAG_DEFER_FREE)
 		ion_heap_freelist_add(heap, buffer);
@@ -694,8 +660,6 @@ static int ion_device_create(void)
 	}
 
 	idev->debug_root = debugfs_create_dir("ion", NULL);
-	idev->buffers = RB_ROOT;
-	mutex_init(&idev->buffer_lock);
 	init_rwsem(&idev->lock);
 	plist_head_init(&idev->heaps);
 	internal_dev = idev;

drivers/staging/android/ion/ion.h

@@ -23,7 +23,6 @@
 
 /**
  * struct ion_buffer - metadata for a particular buffer
- * @node:		node in the ion_device buffers tree
  * @list:		element in list of deferred freeable buffers
  * @dev:		back pointer to the ion_device
  * @heap:		back pointer to the heap the buffer came from
@@ -39,10 +38,7 @@
  * @attachments:	list of devices attached to this buffer
  */
 struct ion_buffer {
-	union {
-		struct rb_node node;
-		struct list_head list;
-	};
+	struct list_head list;
 	struct ion_device *dev;
 	struct ion_heap *heap;
 	unsigned long flags;
@@ -61,14 +57,10 @@ void ion_buffer_destroy(struct ion_buffer *buffer);
 /**
  * struct ion_device - the metadata of the ion device node
  * @dev:		the actual misc device
- * @buffers:		an rb tree of all the existing buffers
- * @buffer_lock:	lock protecting the tree of buffers
  * @lock:		rwsem protecting the tree of heaps and clients
  */
 struct ion_device {
 	struct miscdevice dev;
-	struct rb_root buffers;
-	struct mutex buffer_lock;
 	struct rw_semaphore lock;
 	struct plist_head heaps;
 	struct dentry *debug_root;