[PATCH 1/2] zsmalloc: use page->private instead of page->first_page

We are going to rework how compound_head() work. It will not use page->first_page as we have it now. The only other user of page->fisrt_page beyond compound pages is zsmalloc. Let's use page->private instead of page->first_page here. It occupies the same storage space. Signed-off-by: Kirill A.

[PATCH 1/2] zsmalloc: use page-private instead of page-first_page

We are going to rework how compound_head() work. It will not use page-first_page as we have it now. The only other user of page-fisrt_page beyond compound pages is zsmalloc. Let's use page-private instead of page-first_page here. It occupies the same storage space. Signed-off-by: Kirill A.