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发信人: GyeaonWoo (柏林恋人), 信区: Linux
标  题: Linus's Linux--fs/block_dev.c
发信站: 荔园晨风BBS站 (Mon Aug 25 20:02:28 2003), 站内信件

#include <errno.h>

#include <linux/fs.h>
#include <linux/kernel.h>
#include <asm/segment.h>

#define NR_BLK_DEV ((sizeof (rd_blk))/(sizeof (rd_blk[0])))

int block_write(int dev, long * pos, char * buf, int count)
{
        int block = *pos / BLOCK_SIZE;
        int offset = *pos % BLOCK_SIZE;
        int chars;
        int written = 0;
        struct buffer_head * bh;
        register char * p;

        while (count>0) {
                bh = bread(dev,block);
                if (!bh)
                        return written?written:-EIO;
                chars = (count<BLOCK_SIZE) ? count : BLOCK_SIZE;
                p = offset + bh->b_data;
                offset = 0;
                block++;
                *pos += chars;
                written += chars;
                count -= chars;
                while (chars-->0)
                        *(p++) = get_fs_byte(buf++);
                bh->b_dirt = 1;
                brelse(bh);
        }
        return written;
}

int block_read(int dev, unsigned long * pos, char * buf, int count)
{
        int block = *pos / BLOCK_SIZE;
        int offset = *pos % BLOCK_SIZE;
        int chars;
        int read = 0;
        struct buffer_head * bh;
        register char * p;

        while (count>0) {
                bh = bread(dev,block);
                if (!bh)
                        return read?read:-EIO;
                chars = (count<BLOCK_SIZE) ? count : BLOCK_SIZE;
                p = offset + bh->b_data;
                offset = 0;
                block++;
                *pos += chars;
                read += chars;
                count -= chars;
                while (chars-->0)
                        put_fs_byte(*(p++),buf++);
                bh->b_dirt = 1;
                brelse(bh);
        }
        return read;
}

extern void rw_hd(int rw, struct buffer_head * bh);

typedef void (*blk_fn)(int rw, struct buffer_head * bh);

static blk_fn rd_blk[]={
        NULL,           /* nodev */
        NULL,           /* dev mem */
        NULL,           /* dev fd */
        rw_hd,          /* dev hd */
        NULL,           /* dev ttyx */
        NULL,           /* dev tty */
        NULL};          /* dev lp */

void ll_rw_block(int rw, struct buffer_head * bh)
{
        blk_fn blk_addr;
        unsigned int major;

        if ((major=MAJOR(bh->b_dev)) >= NR_BLK_DEV ||
!(blk_addr=rd_blk[major]))
                panic("Trying to read nonexistent block-device");
        blk_addr(rw, bh);
}

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