file.c

elinux jffs初始版本 具体了解JFFS的文件系统！

/*
 *  linux/fs/affs/file.c
 *
 *  (c) 1996  Hans-Joachim Widmaier - Rewritten
 *
 *  (C) 1993  Ray Burr - Modified for Amiga FFS filesystem.
 *
 *  (C) 1992  Eric Youngdale Modified for ISO9660 filesystem.
 *
 *  (C) 1991  Linus Torvalds - minix filesystem
 *
 *  affs regular file handling primitives
 */

#include <asm/segment.h>
#include <asm/system.h>
#include <linux/sched.h>
#include <linux/affs_fs.h>
#include <linux/fcntl.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/stat.h>
#include <linux/locks.h>
#include <linux/dirent.h>
#include <linux/fs.h>
#include <linux/amigaffs.h>
#include <linux/mm.h>
#include <linux/pagemap.h>

#define MIN(a,b) (((a)<(b))?(a):(b))
#define MAX(a,b) (((a)>(b))?(a):(b))

static int affs_file_read_ofs(struct inode *inode, struct file *filp, char *buf, int count);
static int affs_file_write(struct inode *inode, struct file *filp, const char *buf, int count);
static int affs_file_write_ofs(struct inode *inode, struct file *filp, const char *buf, int count);
static void affs_release_file(struct inode *inode, struct file *filp);

static struct file_operations affs_file_operations = {
	NULL,			/* lseek - default */
	generic_file_read,	/* read */
	affs_file_write,	/* write */
	NULL,			/* readdir - bad */
	NULL,			/* select - default */
	NULL,			/* ioctl - default */
	generic_file_mmap,	/* mmap */
	NULL,			/* no special open is needed */
	affs_release_file,	/* release */
	file_fsync		/* brute force, but works */
};

struct inode_operations affs_file_inode_operations = {
	&affs_file_operations,	/* default file operations */
	NULL,			/* create */
	NULL,			/* lookup */
	NULL,			/* link */
	NULL,			/* unlink */
	NULL,			/* symlink */
	NULL,			/* mkdir */
	NULL,			/* rmdir */
	NULL,			/* mknod */
	NULL,			/* rename */
	NULL,			/* readlink */
	NULL,			/* follow_link */
	generic_readpage,	/* readpage */
	NULL,			/* writepage */
	affs_bmap,		/* bmap */
	affs_truncate,		/* truncate */
	NULL,			/* permission */
	NULL			/* smap */
};

static struct file_operations affs_file_operations_ofs = {
	NULL,			/* lseek - default */
	affs_file_read_ofs,	/* read */
	affs_file_write_ofs,	/* write */
	NULL,			/* readdir - bad */
	NULL,			/* select - default */
	NULL,			/* ioctl - default */
	NULL,			/* mmap */
	NULL,			/* no special open is needed */
	affs_release_file,	/* release */
	file_fsync		/* brute force, but works */
};

struct inode_operations affs_file_inode_operations_ofs = {
	&affs_file_operations_ofs,	/* default file operations */
	NULL,			/* create */
	NULL,			/* lookup */
	NULL,			/* link */
	NULL,			/* unlink */
	NULL,			/* symlink */
	NULL,			/* mkdir */
	NULL,			/* rmdir */
	NULL,			/* mknod */
	NULL,			/* rename */
	NULL,			/* readlink */
	NULL,			/* follow_link */
	NULL,			/* readpage */
	NULL,			/* writepage */
	NULL,			/* bmap */
	affs_truncate,		/* truncate */
	NULL,			/* permission */
	NULL			/* smap */
};

int
affs_bmap(struct inode *inode, int block)
{
	struct buffer_head	*bh;
	int			 ext, key;
	int			 ptype, stype;

	pr_debug("AFFS: bmap(%lu,%d)\n",inode->i_ino,block);

	if (block < 0) {
		printk("affs_bmap: block < 0\n");
		return 0;
	}

	/* If this is a hard link, quietly exchange the inode with the original */

	key = inode->u.affs_i.i_original ? inode->u.affs_i.i_original : inode->i_ino;

	ext = block / AFFS_I2HSIZE(inode);
	if (ext) {
		if (ext > inode->u.affs_i.i_max_ext)
			ext = inode->u.affs_i.i_max_ext;
		if (ext)
			key = inode->u.affs_i.i_ext[ext -  1];
		block -= ext * AFFS_I2HSIZE(inode);
	}

	for (;;) {
		bh = affs_bread(inode->i_dev,key,AFFS_I2BSIZE(inode));
		if (!bh)
			return 0;
		if (affs_checksum_block(AFFS_I2BSIZE(inode),bh->b_data,&ptype,&stype) ||
		    (ptype != T_SHORT && ptype != T_LIST) || stype != ST_FILE) {
			affs_brelse(bh);
			return 0;
		}
		if (block < AFFS_I2HSIZE(inode))
			break;
		block -= AFFS_I2HSIZE(inode);
		key    = htonl(FILE_END(bh->b_data,inode)->extension);
		affs_brelse(bh);
		if (ext < EXT_CACHE_SIZE - 1) {
			inode->u.affs_i.i_ext[ext] = key;
			inode->u.affs_i.i_max_ext  = ++ext;
		}
	}
	key = AFFS_GET_HASHENTRY(bh->b_data,(AFFS_I2HSIZE(inode) - 1) - block);
	affs_brelse(bh);
	return key;
}

struct buffer_head *
affs_getblock(struct inode *inode, int block)
{
	struct buffer_head	*bh;
	struct buffer_head	*ebh;
	int			 key;
	int			 ext;
	int			 cnt, j, pt;

	pr_debug("AFFS: getblock(%lu,%d)\n",inode->i_ino,block);

	if (block < 0)
		return NULL;
	key = inode->i_ino;
	pt  = T_SHORT;

	ext = block / AFFS_I2HSIZE(inode);
	if (ext) {
		if (ext > inode->u.affs_i.i_max_ext)
			ext = inode->u.affs_i.i_max_ext;
		if (ext) {
			key    = inode->u.affs_i.i_ext[ext - 1];
			block -= ext * AFFS_I2HSIZE(inode);
			pt     = T_LIST;
		}
	}

	for (;;) {
		bh = affs_bread(inode->i_dev,key,AFFS_I2BSIZE(inode));
		if (!bh)
			return NULL;
		if (affs_checksum_block(AFFS_I2BSIZE(inode),bh->b_data,&cnt,&j) ||
		    cnt != pt || j != ST_FILE) {
		    	printk("AFFS: getblock(): inode %d is not a valid %s\n",key,
			       pt == T_SHORT ? "file header" : "extension block");
			affs_brelse(bh);
			return NULL;
		}
		j = htonl(((struct file_front *)bh->b_data)->block_count);
		while (j < AFFS_I2HSIZE(inode) && j <= block) {
			key = affs_new_data(inode);
			if (!key)
				break;
			lock_super(inode->i_sb);
			if (AFFS_BLOCK(bh->b_data,inode,j)) {
				unlock_super(inode->i_sb);
				printk("AFFS: getblock(): block already allocated\n");
				affs_free_block(inode->i_sb,key);
				j++;
				continue;
			}
			unlock_super(inode->i_sb);
			AFFS_BLOCK(bh->b_data,inode,j) = ntohl(key);
			j++;
		}
		if (pt == T_SHORT)
			((struct file_front *)bh->b_data)->first_data =
								AFFS_BLOCK(bh->b_data,inode,0);
		((struct file_front *)bh->b_data)->block_count = ntohl(j);
		affs_fix_checksum(AFFS_I2BSIZE(inode),bh->b_data,5);
		mark_buffer_dirty(bh,1);

		if (block < j)
			break;
		if (j < AFFS_I2HSIZE(inode)) {
			affs_brelse(bh);
			return NULL;
		}

		block -= AFFS_I2HSIZE(inode);
		key    = htonl(FILE_END(bh->b_data,inode)->extension);
		if (!key) {
			key = affs_new_header(inode);
			if (!key) {
				affs_brelse(bh);
				return NULL;
			}
			ebh = affs_bread(inode->i_dev,key,AFFS_I2BSIZE(inode));
			if (!ebh) {
				affs_free_block(inode->i_sb,key);
				return NULL;
			}
			((struct file_front *)ebh->b_data)->primary_type = ntohl(T_LIST);
			((struct file_front *)ebh->b_data)->own_key      = ntohl(key);
			FILE_END(ebh->b_data,inode)->secondary_type      = ntohl(ST_FILE);
			FILE_END(ebh->b_data,inode)->parent              = ntohl(inode->i_ino);
			affs_fix_checksum(AFFS_I2BSIZE(inode),ebh->b_data,5);
			FILE_END(bh->b_data,inode)->extension = ntohl(key);
			affs_fix_checksum(AFFS_I2BSIZE(inode),bh->b_data,5);
			mark_buffer_dirty(bh,1);
			affs_brelse(bh);
			bh = ebh;
		}
		affs_brelse(bh);
		pt = T_LIST;
		if (ext < EXT_CACHE_SIZE - 1) {
			inode->u.affs_i.i_ext[ext] = key;
			inode->u.affs_i.i_max_ext  = ++ext;
		}
	}
	key = htonl(AFFS_BLOCK(bh->b_data,inode,block));
	affs_brelse(bh);
	if (!key)
		return NULL;
	
	return affs_bread(inode->i_dev,key,AFFS_I2BSIZE(inode));
}

struct buffer_head *
affs_getblock_ofs(struct inode *inode, int block, int *blk_key)
{
	struct buffer_head	*bh;
	struct buffer_head	*pbh;
	struct buffer_head	*ebh;
	int			 key;
	int			 ext;
	int			 cnt, j, pt;

	pr_debug("AFFS: getblock_ofs(%lu,%d)\n",inode->i_ino,block);

	if (block < 0)
		return NULL;
	key = inode->i_ino;
	pt  = T_SHORT;

	ext = block / AFFS_I2HSIZE(inode);
	if (ext) {
		if (ext > inode->u.affs_i.i_max_ext)
			ext = inode->u.affs_i.i_max_ext;
		if (ext) {
			key    = inode->u.affs_i.i_ext[ext - 1];
			block -= ext * AFFS_I2HSIZE(inode);
			pt     = T_LIST;
		}
	}

	pbh = NULL;
	for (;;) {
		bh = affs_bread(inode->i_dev,key,AFFS_I2BSIZE(inode));
		if (!bh)
			return NULL;
		if (affs_checksum_block(AFFS_I2BSIZE(inode),bh->b_data,&cnt,&j) ||
		    cnt != pt || j != ST_FILE) {
		    	printk("AFFS: getblock(): inode %d is not a valid %s\n",key,
			       pt == T_SHORT ? "file header" : "extension block");
			affs_brelse(bh);
			return NULL;
		}
		j = htonl(((struct file_front *)bh->b_data)->block_count);
		while (j < AFFS_I2HSIZE(inode) && j <= block) {
			if (!pbh && inode->u.affs_i.i_lastblock >= 0) {
				if (j > 0)
					pbh = affs_bread(inode->i_dev,ntohl(AFFS_BLOCK(bh->b_data,inode,j - 1)),
							 AFFS_I2BSIZE(inode));
				else
					pbh = affs_getblock_ofs(inode,inode->u.affs_i.i_lastblock,&key);
				if (!pbh) {
					printk("AFFS: getblock(): cannot get last block in file\n");
					break;
				}
			}
			key = affs_new_data(inode);
			if (!key)
				break;
			lock_super(inode->i_sb);
			if (AFFS_BLOCK(bh->b_data,inode,j)) {
				unlock_super(inode->i_sb);
				printk("AFFS: getblock(): block already allocated\n");
				affs_free_block(inode->i_sb,key);
				j++;
				continue;
			}
			AFFS_BLOCK(bh->b_data,inode,j) = ntohl(key);
			unlock_super(inode->i_sb);
			ebh = affs_bread(inode->i_dev,key,AFFS_I2BSIZE(inode));
			if (!ebh) {
				printk("AFFS: getblock(): cannot get block %d\n",key);
				affs_free_block(inode->i_sb,key);
				AFFS_BLOCK(bh->b_data,inode,j) = 0;
				break;
			}
			inode->u.affs_i.i_lastblock++;
			DATA_FRONT(ebh)->primary_type    = ntohl(T_DATA);
			DATA_FRONT(ebh)->header_key      = ntohl(inode->i_ino);
			DATA_FRONT(ebh)->sequence_number = ntohl(inode->u.affs_i.i_lastblock + 1);
			if (pbh) {
				DATA_FRONT(pbh)->data_size = ntohl(AFFS_I2BSIZE(inode) - 24);
				DATA_FRONT(pbh)->next_data = ntohl(key);
				affs_fix_checksum(AFFS_I2BSIZE(inode),pbh->b_data,5);
				mark_buffer_dirty(pbh,0);
				mark_buffer_dirty(ebh,0);
				affs_brelse(pbh);
			}
			pbh = ebh;
			j++;
		}
		if (pt == T_SHORT)
			((struct file_front *)bh->b_data)->first_data =
								AFFS_BLOCK(bh->b_data,inode,0);
		((struct file_front *)bh->b_data)->block_count = ntohl(j);
		affs_fix_checksum(AFFS_I2BSIZE(inode),bh->b_data,5);
		mark_buffer_dirty(bh,1);

		if (block < j) {
			if (pbh)
				affs_brelse(pbh);
			break;
		}
		if (j < AFFS_I2HSIZE(inode)) {
			affs_brelse(bh);
			return NULL;
		}

		block -= AFFS_I2HSIZE(inode);
		key    = htonl(FILE_END(bh->b_data,inode)->extension);
		if (!key) {
			key = affs_new_header(inode);
			if (!key) {
				affs_brelse(bh);
				return NULL;
			}
			ebh = affs_bread(inode->i_dev,key,AFFS_I2BSIZE(inode));
			if (!ebh) {
				affs_free_block(inode->i_sb,key);
				return NULL;
			}
			((struct file_front *)ebh->b_data)->primary_type = ntohl(T_LIST);
			((struct file_front *)ebh->b_data)->own_key      = ntohl(key);
			FILE_END(ebh->b_data,inode)->secondary_type      = ntohl(ST_FILE);
			FILE_END(ebh->b_data,inode)->parent              = ntohl(inode->i_ino);
			affs_fix_checksum(AFFS_I2BSIZE(inode),ebh->b_data,5);
			FILE_END(bh->b_data,inode)->extension = ntohl(key);
			affs_fix_checksum(AFFS_I2BSIZE(inode),bh->b_data,5);
			mark_buffer_dirty(bh,1);
			affs_brelse(bh);
			bh = ebh;
		}