inode.c

elinux jffs初始版本 具体了解JFFS的文件系统！

		/* next entry */
		offset = ntohl(ri.next) & ROMFH_MASK;
	}

	/* Hard link handling */
	if ((ntohl(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
		offset = ntohl(ri.spec) & ROMFH_MASK;

	res = 0;
	if (!(*result = iget(dir->i_sb, offset)))
		res = -EACCES;

out:
	iput(dir);
	return res;
}

/*
 * Ok, we do readpage, to be able to execute programs.  Unfortunately,
 * we can't use bmap, since we have looser alignments.
 */

static int
romfs_readpage(struct inode * inode, struct page * page)
{
	unsigned long buf;
	unsigned long offset, avail, readlen;
	int result = -EIO;

	page->count++;
	set_bit(PG_locked, &page->flags);

	buf = page_address(page);
	clear_bit(PG_uptodate, &page->flags);
	clear_bit(PG_error, &page->flags);
	offset = page->offset;
	if (offset < inode->i_size) {
		avail = inode->i_size-offset;
		readlen = min(avail, PAGE_SIZE);
		if (romfs_copyfrom(inode, (void *)buf, inode->u.romfs_i.i_dataoffset+offset, readlen) == readlen) {
			if (readlen < PAGE_SIZE) {
				memset((void *)(buf+readlen),0,PAGE_SIZE-readlen);
			}
			set_bit(PG_uptodate, &page->flags);
			result = 0;
		}
	}
	if (result) {
		set_bit(PG_error, &page->flags);
		memset((void *)buf, 0, PAGE_SIZE);
	}

	clear_bit(PG_locked, &page->flags);
	wake_up(&page->wait);
	free_page(buf);

	return result;
}

#ifdef MAGIC_ROM_PTR
static int
romfs_romptr(struct inode * inode, struct file * filp, struct vm_area_struct * vma)
{
	vma->vm_offset += inode->u.romfs_i.i_dataoffset;

	if ((vma->vm_flags & VM_WRITE) || bromptr(inode->i_dev, vma))
		return -ENOSYS;

	return 0;
}
#endif

static int
romfs_readlink(struct inode *inode, char *buffer, int len)
{
	int mylen;
	char buf[ROMFS_MAXFN];		/* XXX dynamic */

	if (!inode || !S_ISLNK(inode->i_mode)) {
		mylen = -EBADF;
		goto out;
	}

	mylen = min(sizeof(buf), inode->i_size);

	if (romfs_copyfrom(inode, buf, inode->u.romfs_i.i_dataoffset, mylen) <= 0) {
		mylen = -EIO;
		goto out;
	}
	memcpy_tofs(buffer, buf, mylen);

out:
	iput(inode);
	return mylen;
}

static int
romfs_follow_link(struct inode *dir, struct inode *inode,
	int flag, int mode, struct inode **res_inode)
{
	int error, len;
	char *buf;

	*res_inode = NULL;
	if (!dir) {
		dir = current->fs->root;
		dir->i_count++;
	}

	if (!inode) {
		iput(dir);
		return -ENOENT;
	}
	if (!S_ISLNK(inode->i_mode)) {
		*res_inode = inode;
		iput(dir);
		return 0;
	}
	if (current->link_count > 5) {
		iput(inode);
		iput(dir);
		return -ELOOP;
	}

	/* Eek. Short enough. */
	len = inode->i_size;
	if (!(buf = kmalloc(len+1, GFP_KERNEL))) {
		iput(inode);
		iput(dir);
		/* correct?  spin? */
		return -EAGAIN;
	}
	error = romfs_copyfrom(inode, buf, inode->u.romfs_i.i_dataoffset, len);
	if (error != len) {
		iput(inode);
		iput(dir);
		error = -EIO;
	} else {
		iput(inode);
		buf[len] = 0;
		current->link_count++;
		error = open_namei(buf, flag, mode, res_inode, dir);
		current->link_count--;
	}

	kfree(buf);
	return error;
}

/* Mapping from our types to the kernel */

static struct file_operations romfs_file_operations = {
	NULL,			/* lseek - default */
        generic_file_read,	/* read */
	NULL,			/* write - bad */
	NULL,			/* readdir */
	NULL,			/* select - default */
	NULL,			/* ioctl */
	generic_file_mmap,	/* mmap */
	NULL,			/* open */
	NULL,			/* release */
	NULL,			/* fsync */
	NULL,			/* fasync */
	NULL,			/* check_media_change */
	NULL,			/* revalidate */
#ifdef MAGIC_ROM_PTR
	romfs_romptr,		/* romptr */
#endif
};

static struct inode_operations romfs_file_inode_operations = {
	&romfs_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 */
	romfs_readpage,		/* readpage */
	NULL,			/* writepage */
	NULL,			/* bmap -- not really */
	NULL,			/* truncate */
	NULL,			/* permission */
	NULL,			/* smap */
};

static struct file_operations romfs_dir_operations = {
	NULL,			/* lseek - default */
        NULL,			/* read */
	NULL,			/* write - bad */
	romfs_readdir,		/* readdir */
	NULL,			/* select - default */
	NULL,			/* ioctl */
	NULL,			/* mmap */
	NULL,			/* open */
	NULL,			/* release */
	NULL,			/* fsync */
	NULL,			/* fasync */
	NULL,			/* check_media_change */
	NULL			/* revalidate */
};

/* Merged dir/symlink op table.  readdir/lookup/readlink/follow_link
 * will protect from type mismatch.
 */

static struct inode_operations romfs_dirlink_inode_operations = {
	&romfs_dir_operations,
	NULL,			/* create */
	romfs_lookup,		/* lookup */
	NULL,			/* link */
	NULL,			/* unlink */
	NULL,			/* symlink */
	NULL,			/* mkdir */
	NULL,			/* rmdir */
	NULL,			/* mknod */
	NULL,			/* rename */
	romfs_readlink,		/* readlink */
	romfs_follow_link,	/* follow_link */
	NULL,			/* readpage */
	NULL,			/* writepage */
	NULL,			/* bmap */
	NULL,			/* truncate */
	NULL,			/* permission */
	NULL,			/* smap */
};

static mode_t romfs_modemap[] =
{
	0, S_IFDIR, S_IFREG, S_IFLNK+0777,
	S_IFBLK, S_IFCHR, S_IFSOCK, S_IFIFO
};

static struct inode_operations *romfs_inoops[] =
{
	NULL,				/* hardlink, handled elsewhere */
	&romfs_dirlink_inode_operations,
	&romfs_file_inode_operations,
	&romfs_dirlink_inode_operations,
	&blkdev_inode_operations,	/* standard handlers */
	&chrdev_inode_operations,
	NULL,				/* socket */
	NULL,				/* fifo */
};

static void
romfs_read_inode(struct inode *i)
{
	int nextfh, ino;
	struct romfs_inode ri;

	ino = i->i_ino & ROMFH_MASK;

	i->i_op = NULL;
	i->i_mode = 0;

	/* Loop for finding the real hard link */
	for(;;) {
		if (romfs_copyfrom(i, &ri, ino, ROMFH_SIZE) <= 0) {
			printk("romfs: read error for inode 0x%x\n", ino);
			return;
		}
		/* XXX: do romfs_checksum here too (with name) */

		nextfh = ntohl(ri.next);
		if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
			break;

		ino = ntohl(ri.spec) & ROMFH_MASK;
	}

	i->i_nlink = 1;		/* Hard to decide.. */
	i->i_size = ntohl(ri.size);
	i->i_mtime = i->i_atime = i->i_ctime = 0;
	i->i_uid = i->i_gid = 0;

	i->i_op = romfs_inoops[nextfh & ROMFH_TYPE];

	/* Precalculate the data offset */
	ino = romfs_strnlen(i, ino+ROMFH_SIZE, ROMFS_MAXFN);
	if (ino >= 0)
		ino = ((ROMFH_SIZE+ino+1+ROMFH_PAD)&ROMFH_MASK);
	else
		ino = 0;

	i->u.romfs_i.i_metasize = ino;
	i->u.romfs_i.i_dataoffset = ino+(i->i_ino&ROMFH_MASK);

	/* Compute permissions */
	ino = S_IRUGO|S_IWUSR;
	ino |= romfs_modemap[nextfh & ROMFH_TYPE];
	if (nextfh & ROMFH_EXEC) {
		ino |= S_IXUGO;
	}
	i->i_mode = ino;

	if (S_ISFIFO(ino))
		init_fifo(i);
	else if (S_ISDIR(ino))
		i->i_size = i->u.romfs_i.i_metasize;
	else if (S_ISBLK(ino) || S_ISCHR(ino)) {
		i->i_mode |= S_IRWXG | S_IRWXO; /* permission to write for all */
		/*i->i_mode &= ~(S_IRWXG|S_IRWXO);*/
		ino = ntohl(ri.spec);
		i->i_rdev = MKDEV(ino>>16,ino&0xffff);
	}
}

static struct super_operations romfs_ops = {
	romfs_read_inode,	/* read inode */
	NULL,			/* notify change */
	NULL,			/* write inode */
	NULL,			/* put inode */
	romfs_put_super,	/* put super */
	NULL,			/* write super */
	romfs_statfs,		/* statfs */
	NULL			/* remount */
};

static struct file_system_type romfs_fs_type = {
	romfs_read_super, "romfs", 1, NULL
};

int
init_romfs_fs(void)
{
	return register_filesystem(&romfs_fs_type);
}

#ifdef MODULE

/* Yes, works even as a module... :) */

int
init_module(void)
{
	int status;

	if ((status = init_romfs_fs()) == 0)
		register_symtab(0);
	return status;
}

void
cleanup_module(void)
{
	unregister_filesystem(&romfs_fs_type);
}
#endif