本章列出了Linux实用的主要数据结构。
　　
　　block_dev_struct
　　
　　　　此结构用于向核心登记块设备，它还被buffer cache实用。所有此类结构都位于blk_dev数组中。
　　
　　struct blk_dev_struct {
　　void (*request_fn)(void);
　　struct request * current_request;
　　struct request plug;
　　struct tq_struct plug_tq;
　　};
　　buffer_head
　　
　　　　此结构包含关于buffer cache中一块缓存的信息。
　　
　　/* bh state bits */
　　#define BH_Uptodate 0 /* 1 if the buffer contains valid data */
　　#define BH_Dirty 1 /* 1 if the buffer is dirty */
　　#define BH_Lock 2 /* 1 if the buffer is locked */
　　#define BH_Req 3 /* 0 if the buffer has been invalidated */
　　#define BH_Touched 4 /* 1 if the buffer has been touched (aging) */
　　#define BH_Has_aged 5 /* 1 if the buffer has been aged (aging) */
　　#define BH_Protected 6 /* 1 if the buffer is protected */
　　#define BH_FreeOnIO 7 /* 1 to discard the buffer_head after IO */
　　struct buffer_head {
　　/* First cache line: */
　　unsigned long b_blocknr; /* block number */
　　kdev_t b_dev; /* device (B_FREE = free) */
　　kdev_t b_rdev; /* Real device */
　　unsigned long b_rsector; /* Real buffer location on disk */
　　struct buffer_head *b_next; /* Hash queue list */
　　struct buffer_head *b_this_page; /* circular list of buffers in one
　　page */
　　/* Second cache line: */
　　unsigned long b_state; /* buffer state bitmap (above) */
　　struct buffer_head *b_next_free;
　　unsigned int b_count; /* users using this block */
　　unsigned long b_size; /* block size */
　　/* Non-performance-critical data follows. */
　　char *b_data; /* pointer to data block */
　　unsigned int b_list; /* List that this buffer appears */
　　unsigned long b_flushtime; /* Time when this (dirty) buffer
　　* should be written */
　　unsigned long b_lru_time; /* Time when this buffer was
　　* last used. */
　　struct wait_queue *b_wait;
　　struct buffer_head *b_prev; /* doubly linked hash list */
　　struct buffer_head *b_prev_free; /* doubly linked list of buffers */
　　struct buffer_head *b_reqnext; /* request queue */
　　};
　　device
　　
　　　　系统中每个网络设备都用一个设备数据结构来表示。
　　
　　struct device
　　{
　　/*
　　* This is the first field of the visible part of this structure
　　* (i.e. as seen by users in the Space.c file). It is the name
　　* the interface.
　　*/
　　char *name;
　　/* I/O specific fields */
　　unsigned long rmem_end; /* shmem recv end */
　　unsigned long rmem_start; /* shmem recv start */
　　unsigned long mem_end; /* shared mem end */
　　unsigned long mem_start; /* shared mem start */
　　unsigned long base_addr; /* device I/O address */
　　unsigned char irq; /* device IRQ number */
　　/* Low-level status flags. */
　　volatile unsigned char start, /* start an operation */
　　interrupt; /* interrupt arrived */
　　unsigned long tbusy; /* transmitter busy */
　　struct device *next;
　　/* The device initialization function. Called only once. */
　　int (*init)(struct device *dev);
　　/* Some hardware also needs these fields, but they are not part of
　　the usual set specified in Space.c. */
　　unsigned char if_port; /* Selectable AUI,TP, */