struct page*

struct 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 */

        };

        union {

                pgoff_t index;          /* Our offset within mapping. */

                void *freelist;         /* SLUB: freelist req. slab lock */

        };

        struct list_head lru;           /* Pageout list, eg. active_list

                                         * protected by zone->lru_lock !

                                         */

        /*

         * On machines where all RAM is mapped into kernel address space,

         * we can simply calculate the virtual address. On machines with

         * highmem some memory is mapped into kernel virtual memory

         * dynamically, so we need a place to store that address.

         * Note that this field could be 16 bits on x86 ... ;)

         *

         * Architectures with slow multiplication can define

         * WANT_PAGE_VIRTUAL in asm/page.h

         */

#if defined(WANT_PAGE_VIRTUAL)

        void *virtual;                  /* Kernel virtual address (NULL if

                                           not kmapped, ie. highmem) */

#endif /* WANT_PAGE_VIRTUAL */

#ifdef CONFIG_WANT_PAGE_DEBUG_FLAGS

        unsigned long debug_flags;      /* Use atomic bitops on this */

#endif



#ifdef CONFIG_KMEMCHECK

        /*

         * kmemcheck wants to track the status of each byte in a page; this

         * is a pointer to such a status block. NULL if not tracked.

         */

        void *shadow;

#endif

};



/*

 * A region containing a mapping of a non-memory backed file under NOMMU

 * conditions.  These are held in a global tree and are pinned by the VMAs that

 * map parts of them.

 */

struct vm_region {

        struct rb_node  vm_rb;          /* link in global region tree */

        unsigned long   vm_flags;       /* VMA vm_flags */

        unsigned long   vm_start;       /* start address of region */

        unsigned long   vm_end;         /* region initialised to here */

        unsigned long   vm_top;         /* region allocated to here */

        unsigned long   vm_pgoff;       /* the offset in vm_file corresponding to vm_start */

        struct file     *vm_file;       /* the backing file or NULL */



        int             vm_usage;       /* region usage count (access under nommu_region_sem) */

        bool            vm_icache_flushed : 1; /* true if the icache has been flushed for

                                                * this region */

};

　　1 unsigned long flags

unsigned long flags

//flags在page-flags.h文件夹中枚举

//paging_init()可设置PG_reserved做flags

//mem_init()可设置含PG_reserved的flags清除

//#define PG_reserved 11;表示页保留，无法被__free_page()回收

 

　　2 atomic_t _count和atumic_t _mapcount 

atomic_t _count;          //页引用计数器

atomic_t _mapcount;    //页映射计数器

//paging_init()可以将它们初始化为-1

//mem_init()可以将所有位码为0的页的_count设置为0

//page_count和page_mapcount可以统计其实用者个数

//_count+1为页使用者个数，_mapcount+1为页共享者个数

// _count为-1时不可被__free_page()释放

//_mapcount为0表示该页未被共享

　　3 unsigned long private

unsigned long private;        //私有数据指针

//设置为PG_private，则private字段指向struct buffer_head

//设置为PG_compound，则指向struct page

//设置为PG_swapcache，则private为swp_entry_t的成员变量val

 

　　4 struct address_space *mapping

struct address_space *mapping；  //该页所在地址空间描述结构指针

/*page->mapping == 0 属于交换高速缓存页

*page->mapping != 0 且第0位为1，为匿名页，指向struct anon_vma

*page->mapping != 0 且第0位为0，指向struct address_space地址空间结构变量

*/

　　5 pgoff_t index

pgoff_t index; 

//该页描述结构在地址空间radix树page_tree中的对象索引号即页号

//表示该页在vm_file中的便宜页数

//#define unsigned long pgoff_t

　　6 struct list_head lru

struct list_head lru; //最近、最久未使用struct slab结构指针变量

//设置PG_slab，则该页由slab分配器来管理，lru.next指向kmem_cache_t结构变量，lru.prev则指向struct slab结构

 

　　7 struct pagevec

struct pagevec {                //页向量描述结构

        unsigned long nr;       //该页向量中的内存页数

        unsigned long cold;    //冷区标志，0表示热区，非0表示冷区

        struct page *pages[PAGEVEC_SIZE];

        //该也想两种的页描述结构指针数组（PAGEVEC_SIZE=14）

};

　　8 struct page_address_map

struct page_address_map {        //页地址映射

        struct page *page;            //页的描述结构

        void *virtual;                //页的虚拟地址

        struct list_head list;           //通过list字段链接到页表池全局链表page_address_pool中或page_address_htable[hash_ptr(page,PA_HASH_ORDER)].lh

};    

　　9 struct page_address_slot

static struct page_address_slot {

        struct list_head lh;                    /* List of page_address_maps */

        spinlock_t lock;                        /* Protect this bucket's list */

} ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];