1 files changed, 12 insertions, 6 deletions

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 35138f8a375c..b602cd72a120 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -571,12 +571,20 @@ static void drm_gem_shmem_vm_open(struct vm_area_struct *vma)
 {
 	struct drm_gem_object *obj = vma->vm_private_data;
 	struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
-	int ret;
 
 	WARN_ON(shmem->base.import_attach);
 
-	ret = drm_gem_shmem_get_pages(shmem);
-	WARN_ON_ONCE(ret != 0);
+	mutex_lock(&shmem->pages_lock);
+
+	/*
+	 * We should have already pinned the pages when the buffer was first
+	 * mmap'd, vm_open() just grabs an additional reference for the new
+	 * mm the vma is getting copied into (ie. on fork()).
+	 */
+	if (!WARN_ON_ONCE(!shmem->pages_use_count))
+		shmem->pages_use_count++;
+
+	mutex_unlock(&shmem->pages_lock);
 
 	drm_gem_vm_open(vma);
 }
@@ -622,10 +630,8 @@ int drm_gem_shmem_mmap(struct drm_gem_shmem_object *shmem, struct vm_area_struct
 	}
 
 	ret = drm_gem_shmem_get_pages(shmem);
-	if (ret) {
-		drm_gem_vm_close(vma);
+	if (ret)
 		return ret;
-	}
 
 	vma->vm_flags |= VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
 	vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);