Linux Filesystem, Storage, and Memory Management Summit, Day 1

The struct page_cgroup page backpointer is already gone as of .39-rc1. It did not need the LRU rework. Nodes or sparsemem sections hold the struct page_cgroup arrays, so the node or section id is encoded in pc->flags to get from the struct page_cgroup pointer to the array it points into, and then it's trivial to calculate the pfn.