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;
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