Revert "drm/vgem: Implement mmap as GEM object function"

Commit 375cca1c ("drm/vgem: Implement mmap as GEM object function")
broke several IGT tests in vgem_basic. [1] Attempts to fix the issue
have not worked out so far. [2][3] Revert the change for now.

Note that there is a patch that converts vgem to shmem helpers. [4]
Merging this change would be preferable to modifying vgem's mmap code.

v2:
	* fix spelling error in commit message (Daniel)

[1] https://intel-gfx-ci.01.org/tree/drm-tip/igt@vgem_basic@unload.html
[2] https://lore.kernel.org/intel-gfx/20210709154256.12005-1-tzimmermann@suse.de/
[3] https://lore.kernel.org/intel-gfx/20210712123321.3658-1-tzimmermann@suse.de/
[4] https://patchwork.freedesktop.org/series/90671/Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Fixes: 375cca1c ("drm/vgem: Implement mmap as GEM object function")
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Christian König <christian.koenig@amd.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Melissa Wen <melissa.srw@gmail.com>
Cc: Qinglang Miao <miaoqinglang@huawei.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210713090235.26372-1-tzimmermann@suse.de

drivers/gpu/drm/vgem/vgem_drv.c

@@ -239,7 +239,32 @@ static struct drm_ioctl_desc vgem_ioctls[] = {
 	DRM_IOCTL_DEF_DRV(VGEM_FENCE_SIGNAL, vgem_fence_signal_ioctl, DRM_RENDER_ALLOW),
 };
 
-DEFINE_DRM_GEM_FOPS(vgem_driver_fops);
+static int vgem_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+	unsigned long flags = vma->vm_flags;
+	int ret;
+
+	ret = drm_gem_mmap(filp, vma);
+	if (ret)
+		return ret;
+
+	/* Keep the WC mmaping set by drm_gem_mmap() but our pages
+	 * are ordinary and not special.
+	 */
+	vma->vm_flags = flags | VM_DONTEXPAND | VM_DONTDUMP;
+	return 0;
+}
+
+static const struct file_operations vgem_driver_fops = {
+	.owner		= THIS_MODULE,
+	.open		= drm_open,
+	.mmap		= vgem_mmap,
+	.poll		= drm_poll,
+	.read		= drm_read,
+	.unlocked_ioctl = drm_ioctl,
+	.compat_ioctl	= drm_compat_ioctl,
+	.release	= drm_release,
+};
 
 static struct page **vgem_pin_pages(struct drm_vgem_gem_object *bo)
 {
@@ -362,12 +387,24 @@ static void vgem_prime_vunmap(struct drm_gem_object *obj, struct dma_buf_map *ma
 	vgem_unpin_pages(bo);
 }
 
-static int vgem_prime_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)
+static int vgem_prime_mmap(struct drm_gem_object *obj,
+			   struct vm_area_struct *vma)
 {
+	int ret;
+
+	if (obj->size < vma->vm_end - vma->vm_start)
+		return -EINVAL;
+
+	if (!obj->filp)
+		return -ENODEV;
+
+	ret = call_mmap(obj->filp, vma);
+	if (ret)
+		return ret;
+
 	vma_set_file(vma, obj->filp);
 	vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
 	vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
-	vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);
 
 	return 0;
 }
@@ -379,7 +416,6 @@ static const struct drm_gem_object_funcs vgem_gem_object_funcs = {
 	.get_sg_table = vgem_prime_get_sg_table,
 	.vmap = vgem_prime_vmap,
 	.vunmap = vgem_prime_vunmap,
-	.mmap = vgem_prime_mmap,
 	.vm_ops = &vgem_gem_vm_ops,
 };
 
@@ -397,7 +433,7 @@ static const struct drm_driver vgem_driver = {
 	.prime_fd_to_handle = drm_gem_prime_fd_to_handle,
 	.gem_prime_import = vgem_prime_import,
 	.gem_prime_import_sg_table = vgem_prime_import_sg_table,
-	.gem_prime_mmap = drm_gem_prime_mmap,
+	.gem_prime_mmap = vgem_prime_mmap,
 
 	.name	= DRIVER_NAME,
 	.desc	= DRIVER_DESC,