[RFC PATCH 5/9] mm/zbud: encode zbud handle using struct page

As a preparation for further patches, this patch changes the way of encoding zbud handle. Currently, zbud handle is actually just a virtual address that is casted to unsigned long before return back. Exporting the address to clients would be inappropriate if we use highmem pages for zbud pages,

[RFC PATCH 5/9] mm/zbud: encode zbud handle using struct page

As a preparation for further patches, this patch changes the way of encoding zbud handle. Currently, zbud handle is actually just a virtual address that is casted to unsigned long before return back. Exporting the address to clients would be inappropriate if we use highmem pages for zbud pages,