dma-buf: Move dma_buf_mmap_internal() to dynamic locking specification

All dma-buf functions has been moved to dynamic locking specification
The dma_buf_mmap_internal() was missed out by accident. Take reservation
lock around file mapping operation to adhere the common locking convention.

Reported-by: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221110201349.351294-2-dmitry.osipenko@collabora.com

drivers/dma-buf/dma-buf.c

@@ -129,6 +129,7 @@ static struct file_system_type dma_buf_fs_type = {
 static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
 {
 	struct dma_buf *dmabuf;
+	int ret;
 
 	if (!is_dma_buf_file(file))
 		return -EINVAL;
@@ -144,7 +145,11 @@ static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
 	    dmabuf->size >> PAGE_SHIFT)
 		return -EINVAL;
 
-	return dmabuf->ops->mmap(dmabuf, vma);
+	dma_resv_lock(dmabuf->resv, NULL);
+	ret = dmabuf->ops->mmap(dmabuf, vma);
+	dma_resv_unlock(dmabuf->resv);
+
+	return ret;
 }
 
 static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence)