linux-blk.h

#ifndef _BLK_H #define _BLK_H #define NR_BLK_DEV    7                        //－－块设备类型数量 /* * NR_REQUEST is the number of entries in the request-queue. * NOTE that writes may use only the low 2/3 of these: reads * take precedence. * * 32 seems to be a reasonable number: enough to get some benefit * from the elevator-mechanism, but not so much as to lock a lot of * buffers when they are in the queue. 64 seems to be too many (easily * long pauses in reading when heavy writing/syncing is going on) */ #define NR_REQUEST    32                        //－－ /* * Ok, this is an expanded form so that we can use the same * request for paging requests when that is implemented. In * paging, 'bh' is NULL, and 'waiting' is used to wait for * read/write completion. */ struct request { int dev;        /* -1 if no request */ int cmd;        /* READ or WRITE */ int errors; unsigned long sector;                //－－起始扇区 unsigned long nr_sectors;            //－－读写扇区数 char * buffer;                        //－－数据缓冲区 struct task_struct * waiting;        //－－任务等待请求完成操作的地方 struct buffer_head * bh;            //－－缓冲区头指针 struct request * next;                //－－下一项 }; /* * This is used in the elevator algorithm: Note that * reads always go before writes. This is natural: reads * are much more time-critical than writes. */ #define IN_ORDER(s1,s2) /                //－－电梯算法宏(读操作总在写操作之前)，s1,s2为request指针 ((s1)->cmd<(s2)->cmd || (s1)->cmd==(s2)->cmd && /        //－－判断两个请求的执行顺序 ((s1)->dev < (s2)->dev || ((s1)->dev == (s2)->dev && /    //－－目的:提高读写磁盘的效率，减小磁头移动距离 (s1)->sector < (s2)->sector))) struct blk_dev_struct { void (*request_fn)(void); struct request * current_request; }; extern struct blk_dev_struct blk_dev[NR_BLK_DEV]; extern struct request request[NR_REQUEST]; extern struct task_struct * wait_for_request; extern int * blk_size[NR_BLK_DEV]; #ifdef MAJOR_NR                            //－－主设备号 /* * Add entries as needed. Currently the only block devices * supported are hard-disks and floppies. */ #if (MAJOR_NR == 1) /* ram disk */ #define DEVICE_NAME "ramdisk" #define DEVICE_REQUEST do_rd_request #define DEVICE_NR(device) ((device) & 7) #define DEVICE_ON(device) #define DEVICE_OFF(device) #elif (MAJOR_NR == 2) /* floppy */ #define DEVICE_NAME "floppy" #define DEVICE_INTR do_floppy #define DEVICE_REQUEST do_fd_request #define DEVICE_NR(device) ((device) & 3) #define DEVICE_ON(device) floppy_on(DEVICE_NR(device)) #define DEVICE_OFF(device) floppy_off(DEVICE_NR(device)) #elif (MAJOR_NR == 3) /* harddisk */ #define DEVICE_NAME "harddisk" #define DEVICE_INTR do_hd #define DEVICE_TIMEOUT hd_timeout #define DEVICE_REQUEST do_hd_request #define DEVICE_NR(device) (MINOR(device)/5) #define DEVICE_ON(device) #define DEVICE_OFF(device) #elif /* unknown blk device */ #error "unknown blk device" #endif #define CURRENT (blk_dev[MAJOR_NR].current_request) #define CURRENT_DEV DEVICE_NR(CURRENT->dev) #ifdef DEVICE_INTR                        //－－设备中断处理符号函数 void (*DEVICE_INTR)(void) = NULL; #endif #ifdef DEVICE_TIMEOUT                    //－－设备超时符号函数 int DEVICE_TIMEOUT = 0; #define SET_INTR(x) (DEVICE_INTR = (x),DEVICE_TIMEOUT = 200) #else #define SET_INTR(x) (DEVICE_INTR = (x)) #endif static void (DEVICE_REQUEST)(void); extern inline void unlock_buffer(struct buffer_head * bh)    //－－解锁指定的缓冲块，并唤醒等待该缓冲块的进程 { if (!bh->b_lock) printk(DEVICE_NAME ": free buffer being unlocked/n"); bh->b_lock=0; wake_up(&bh->b_wait); } extern inline void end_request(int uptodate)                //－－结束请求处理 { DEVICE_OFF(CURRENT->dev); if (CURRENT->bh) { CURRENT->bh->b_uptodate = uptodate; unlock_buffer(CURRENT->bh); } if (!uptodate) { printk(DEVICE_NAME " I/O error/n/r"); printk("dev %04x, block %d/n/r",CURRENT->dev, CURRENT->bh->b_blocknr); } wake_up(&CURRENT->waiting); wake_up(&wait_for_request); CURRENT->dev = -1; CURRENT = CURRENT->next; } #ifdef DEVICE_TIMEOUT #define CLEAR_DEVICE_TIMEOUT DEVICE_TIMEOUT = 0; #else #define CLEAR_DEVICE_TIMEOUT #endif #ifdef DEVICE_INTR #define CLEAR_DEVICE_INTR DEVICE_INTR = 0; #else #define CLEAR_DEVICE_INTR #endif #define INIT_REQUEST /                        //－－定义初始化请求宏，用语对当前请求项进行一些有效性判断 repeat: / if (!CURRENT) {/ CLEAR_DEVICE_INTR / CLEAR_DEVICE_TIMEOUT / return; / } / if (MAJOR(CURRENT->dev) != MAJOR_NR) / panic(DEVICE_NAME ": request list destroyed"); / if (CURRENT->bh) { / if (!CURRENT->bh->b_lock) / panic(DEVICE_NAME ": block not locked"); / } #endif #endif |xGv00|fcc8d4de8197f69fde70263fb4d52380

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