struct block_operations{int (*open) (struct inode *,struct file *);int (*release) (struct inode *,struct file*);　　//open()和release()都是同步的int (*ioctl) (struct node *,struct file *,unsigned, unsigned long);int (*media_changed) (struct gendisk *);int (*revalidate_disk) (struct gendisk *);struct module *owner;
};

struct request_queue
{struct list_head queue_head;　　//指向请求队列对首的指针struct request  *last_merge;　　//加到请求队列的最后一个请求elevator_t  elevator;　　　　　　//这个不懂，求大神指教struct request_list rq;　　　　　//由两个wait_queue组成，分别用于块设备读请求队列和写请求队列
...request_fn_proc *request_fn;merge_request_fn *back_merge_fn;merge_request_fn *front_merge_fn;merge_requests_fn *merge_requests_fn;make_request_fn *make_request_fn;prep_rq_fn *prep_rq_fn;unplug_fn *unplug_fn;merge_bvec_fn *merge_bvec_fn;activity_fn *activity_fn;　　　　　　//定义调度程序相关函数来控制如何管理块设备的请求
...struct time_list unplug_timer;int unplug_thresh;unsigned long  unplug_delay;struct work_struct unplug_work;struct backing_dev_info backing_dev_info;　　　　//用于去掉设备的IO调度函数...void *queuedata;void *activity_data;　　//这些是对设备和设备驱动程序相关的队列进行管理...unsigned long  bounce_pfn;int  bounce_gfp;　　　　//是指内核将高端内存缓存冲区的IO请求copy到低端内存缓冲区去unsigned long queue_flags;//变量queue_flags存储一个或者多个队列标志，参见下表格。

spinlock_t *queue_lock;
struct kobject kobj;
unsigned long nr_requests;　　
unsigned int nr_congestion_on;
unsigned int nr_congestion_off;
unsigned short max_sectors;
unsigned short max_phys_segments;
unsigned short max_hw_segments;
unsigned short hardsect_size;
unsigned int max_segment_size;
unsigned long seg_boundary_mask;
unsigned long dma_alignment;
struct blk_queue_tag *queue_tags;
atomic_t refcnt;
unsigned int in_flight;
unsigned int sg_timeout;
unsigned int sg_reserved_size;　　//前面这些变量定义了请求队列中可管理的资源
};

request_queue_t *blk_init_queue(request_fn_proc *rfn,spinlock_t *lock)
{request_queue_t *q;static int printed;q = blk_alloc_queue(GFP_KERNEL);　　//从内核的内存中分配空间队列，内容为0if(!q)return NULL;if(blk_init_free_list(q))　　//初始化请求清单goto out_init;　　　　//表示一直怕goto,懂但不会用if(!printed){printed = 1;printk("Using %s io schedulern",chosen_elevator->elevator_name);}if(elevator_init(q,chosen_elevator))　　//这是个初始化的函数goto out_elv;q->request_fn = rfn;q->back_merge_fn = 11_back_merge_fn;q->front_merge_fn = 11_front_merge_fn;q->merge_requests_fn = 11_merge_requests_fn;q->prep_rq_fn = NULL;q->unplug_fn = generic_unplug_device;q->queue_flags = (1<<QUEUE_FLAG_CLUSTER);q->queue_lock = lock;　　　　//上述赋值是将电梯调度程序相关的函数与该队列关联blk_queue_segment_boundary(q,0xffffffff);　　//检查是否满足最小尺寸blk_queue_make_request(q,__make_request)　　//设置驱动从队列删除blk_queue_max_segment_size(q,MAX_SEGMENT_SIZE);　　//初始化归并段的上限blk_queue_max_hw_segments(q,MAX_HW_SEGMENTS);　　//初始化物理设备可以处理的最大段数blk_queue_max_phys_segments(q,MAX_PHYS_SEGMENTS);　　初始化每一请求的最大物理数目段return q0;　　//返回已经初始化的队列out_elv:blk_cleanup_queue(q);out_init:kmem_cache_free(requestq_cachep,q);return NULL;　　//错误事件中清除内存的一个例程
}

struct request *elv_next_request(request_queue_t *q)

void end_request(struct request *req,int uptodate)　　//在请求队列中传递elev_next_request()获得的参数
{if(!end_that_request_first(req,uptpdate,req->hrad_cur_sectors))　　//传输适合的扇区数{add_disk_randomness(req->rq_disk);　　//加入系统熵池，表示不懂，求大神指教，blkdev_dequeue_request(req);　　//删除请求结构end_that_request_last(req);　　//收集统计信息并且释放可用的数据结构}
}