backref_cache_entry
static_assert(offsetof(struct backref_cache_entry, entry) == 0);
struct backref_cache_entry *entry;
entry = container_of(raw_entry, struct backref_cache_entry, entry);
struct backref_cache_entry *new_entry;
new_entry = kmalloc_obj(struct backref_cache_entry, GFP_NOFS);