In what scenario does set_page_dirty_lock() need to be called

[xuyizhao]

Look at kernel-open/nvidia-drm/nvidia-drm-linux.c, in my opinion, the purpose of calling set_page_dirty_lock() should be to swap out dirty anonymous pages. But, Linux Kernel function get_user_pages() with FOLL_WRITE will set page dirty or set PTE dirty, and earlier versions of Linux kernel already support it. so, is it necessary to call set_page_dirty_lock() before put anonymous pages?