drm/shmem-helpers: vunmap: Don't put pages for dma-buf

dma-buf importing was reworked in commit 7d2cd72a
("drm/shmem-helpers: Simplify dma-buf importing"). Before that commit
drm_gem_shmem_prime_import_sg_table() did set ->pages_use_count=1 and
drm_gem_shmem_vunmap_locked() could call drm_gem_shmem_put_pages()
unconditionally. Now without the use count set, put pages is called also
on dma-bufs. Fix this by only putting pages if it's not imported.
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Fixes: 7d2cd72a ("drm/shmem-helpers: Simplify dma-buf importing")
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Tested-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20210219122203.51130-1-noralf@tronnes.org

drivers/gpu/drm/drm_gem_shmem_helper.c

@@ -357,13 +357,14 @@ static void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem,
 	if (--shmem->vmap_use_count > 0)
 		return;
 
-	if (obj->import_attach)
+	if (obj->import_attach) {
 		dma_buf_vunmap(obj->import_attach->dmabuf, map);
-	else
+	} else {
 		vunmap(shmem->vaddr);
+		drm_gem_shmem_put_pages(shmem);
+	}
 
 	shmem->vaddr = NULL;
-	drm_gem_shmem_put_pages(shmem);
 }
 
 /*