How to refer to the unamed structure in page struct

[Jimmy Pan]

truct page {
        unsigned long flags;            /* Atomic flags, some possibly
                                         * updated asynchronously */
        atomic_t _count;                /* Usage count, see below. */
        union {
                atomic_t _mapcount;     /* Count of ptes mapped in mms,
                                         * to show when page is mapped
                                         * & limit reverse map searches.
                                         */
                struct {                /* SLUB */
                        u16 inuse;
                        u16 objects;
                };
        };
        union {
            struct {
                unsigned long private;          /* Mapping-private opaque data:
                                                 * usually used for buffer_heads
                                                 * if PagePrivate set; used for
                                                 * swp_entry_t if PageSwapCache;
                                                 * indicates order in the buddy
                                                 * system if PG_buddy is set.
                                                 */
                struct address_space *mapping;  /* If low bit clear, points to
                                                 * inode address_space, or NULL.
                                                 * If page mapped as anonymous
                                                 * memory, low bit is set, and
                                                 * it points to anon_vma object:
                                                 * see PAGE_MAPPING_ANON below.
                                                 */
            };
#if USE_SPLIT_PTLOCKS
            spinlock_t ptl;
#endif
            struct kmem_cache *slab;    /* SLUB: Pointer to slab */
            struct page *first_page;    /* Compound tail pages */
        };



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As you can see in the code， the union in the page structure doesn't
have a name, so does
the structure in the union, how to refer to those two?

Thanks in advance,
Jimmy