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相關(guān)文件
	/drivers/md/raid1.c

(1)
struct raid1_private_data {
	mddev_t			*mddev;
	struct mirror_info	mirrors[MD_SB_DISKS];
	int			nr_disks;		//系統(tǒng)中一共有多少個磁盤
	int			raid_disks;
	int			working_disks;		//工作的盤的數(shù)目
	int			last_used;
	unsigned long		next_sect;
	int			sect_count;
	mdk_thread_t		*thread, *resync_thread;
	int			resync_mirrors;
	struct mirror_info	*spare;
	md_spinlock_t		device_lock;

	/*
	 * 所有的raid1的操作所使用的bh都是預(yù)先分配好的，以棧的形式進行組織。
	 * 其實就是單向鏈表，使用的時候從頭開始摘取。
	 * 這樣做主要是為了避免內(nèi)存緊張時候的死鎖。
	 */
	struct buffer_head	*freebh;
	int			freebh_cnt;	/* how many are on the list */
	int			freebh_blocked;

	/* 
	 * 同上，這不過這里是raid1_bh的結(jié)構(gòu)
	 */
	struct raid1_bh		*freer1;
	int			freer1_blocked;
	int			freer1_cnt;

	struct raid1_bh		*freebuf; 	/* each bh_req has a page allocated */
	md_wait_queue_head_t	wait_buffer;

	/* 同步鏡象盤的時候使用 */
	unsigned long	start_active, start_ready,
		start_pending, start_future;
	int	cnt_done, cnt_active, cnt_ready,
		cnt_pending, cnt_future;
	int	phase;
	int	window;
	md_wait_queue_head_t	wait_done;
	md_wait_queue_head_t	wait_ready;
	md_spinlock_t		segment_lock;
};



(2)
struct raid1_bh {
	atomic_t		remaining; 	//用來計數(shù)要完成多少個I/O操作。在回調(diào)中遞減
	
	int			cmd;		//命令類型，READ還是WRITE
	unsigned long		state;
	mddev_t			*mddev;
	struct buffer_head	*master_bh;	//用來存儲文件系統(tǒng)傳下來的那個buffer_head
	struct buffer_head	*mirror_bh_list;//對鏡象盤進行的寫操作的bh都連接到這個指針后面
	struct buffer_head	bh_req;
	struct raid1_bh		*next_r1;	/* next for retry or in free list */
};