/* *  linux/fs/file_dev.c * *  (C) 1991  Linus Torvalds */#include <errno.h>#include <fcntl.h>#include <linux/sched.h>#include <linux/kernel.h>#include <asm/segment.h>#define MIN(a,b) (((a)<(b))?(a):(b))#define MAX(a,b) (((a)>(b))?(a):(b))int file_read(struct m_inode * inode, struct file * filp, char * buf, int count){	int left,chars,nr;	struct buffer_head * bh;	if ((left=count)<=0)		return 0;	while (left) {		if ((nr = bmap(inode,(filp->f_pos)/BLOCK_SIZE))) {			if (!(bh=bread(inode->i_dev,nr)))				break;		} else			bh = NULL;		nr = filp->f_pos % BLOCK_SIZE;		chars = MIN( BLOCK_SIZE-nr , left );		filp->f_pos += chars;		left -= chars;		if (bh) {			char * p = nr + bh->b_data;			while (chars-->0)				put_fs_byte(*(p++),buf++);			brelse(bh);		} else {			while (chars-->0)				put_fs_byte(0,buf++);		}	}	inode->i_atime = CURRENT_TIME;	return (count-left)?(count-left):-ERROR;}int file_write(struct m_inode * inode, struct file * filp, char * buf, int count){	off_t pos;	int block,c;	struct buffer_head * bh;	char * p;	int i=0;/* * ok, append may not work when many processes are writing at the same time * but so what. That way leads to madness anyway. */	if (filp->f_flags & O_APPEND)		pos = inode->i_size;	else		pos = filp->f_pos;	while (i<count) {		if (!(block = create_block(inode,pos/BLOCK_SIZE)))			break;		if (!(bh=bread(inode->i_dev,block)))			break;		c = pos % BLOCK_SIZE;		p = c + bh->b_data;		bh->b_dirt = 1;		c = BLOCK_SIZE-c;		if (c > count-i) c = count-i;		pos += c;		if (pos > inode->i_size) {			inode->i_size = pos;			inode->i_dirt = 1;		}		i += c;		while (c-->0)			*(p++) = get_fs_byte(buf++);		brelse(bh);	}	inode->i_mtime = CURRENT_TIME;	if (!(filp->f_flags & O_APPEND)) {		filp->f_pos = pos;		inode->i_ctime = CURRENT_TIME;	}	return (i?i:-1);}