inode.c

linux 内核源代码

		}
		stored++;
		offset = nextfh & ROMFH_MASK;
	}
out:
	unlock_kernel();
	return stored;
}

static struct dentry *
romfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
{
	unsigned long offset, maxoff;
	int fslen, res;
	struct inode *inode;
	char fsname[ROMFS_MAXFN];	/* XXX dynamic? */
	struct romfs_inode ri;
	const char *name;		/* got from dentry */
	int len;

	res = -EACCES;			/* placeholder for "no data here" */
	offset = dir->i_ino & ROMFH_MASK;
	lock_kernel();
	if (romfs_copyfrom(dir, &ri, offset, ROMFH_SIZE) <= 0)
		goto out;

	maxoff = romfs_maxsize(dir->i_sb);
	offset = be32_to_cpu(ri.spec) & ROMFH_MASK;

	/* OK, now find the file whose name is in "dentry" in the
	 * directory specified by "dir".  */

	name = dentry->d_name.name;
	len = dentry->d_name.len;

	for(;;) {
		if (!offset || offset >= maxoff)
			goto out0;
		if (romfs_copyfrom(dir, &ri, offset, ROMFH_SIZE) <= 0)
			goto out;

		/* try to match the first 16 bytes of name */
		fslen = romfs_strnlen(dir, offset+ROMFH_SIZE, ROMFH_SIZE);
		if (len < ROMFH_SIZE) {
			if (len == fslen) {
				/* both are shorter, and same size */
				romfs_copyfrom(dir, fsname, offset+ROMFH_SIZE, len+1);
				if (strncmp (name, fsname, len) == 0)
					break;
			}
		} else if (fslen >= ROMFH_SIZE) {
			/* both are longer; XXX optimize max size */
			fslen = romfs_strnlen(dir, offset+ROMFH_SIZE, sizeof(fsname)-1);
			if (len == fslen) {
				romfs_copyfrom(dir, fsname, offset+ROMFH_SIZE, len+1);
				if (strncmp(name, fsname, len) == 0)
					break;
			}
		}
		/* next entry */
		offset = be32_to_cpu(ri.next) & ROMFH_MASK;
	}

	/* Hard link handling */
	if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
		offset = be32_to_cpu(ri.spec) & ROMFH_MASK;

	if ((inode = iget(dir->i_sb, offset)))
		goto outi;

	/*
	 * it's a bit funky, _lookup needs to return an error code
	 * (negative) or a NULL, both as a dentry.  ENOENT should not
	 * be returned, instead we need to create a negative dentry by
	 * d_add(dentry, NULL); and return 0 as no error.
	 * (Although as I see, it only matters on writable file
	 * systems).
	 */

out0:	inode = NULL;
outi:	res = 0;
	d_add (dentry, inode);

out:	unlock_kernel();
	return ERR_PTR(res);
}

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

static int
romfs_readpage(struct file *file, struct page * page)
{
	struct inode *inode = page->mapping->host;
	loff_t offset, avail, readlen;
	void *buf;
	int result = -EIO;

	page_cache_get(page);
	lock_kernel();
	buf = kmap(page);
	if (!buf)
		goto err_out;

	/* 32 bit warning -- but not for us :) */
	offset = page_offset(page);
	if (offset < i_size_read(inode)) {
		avail = inode->i_size-offset;
		readlen = min_t(unsigned long, avail, PAGE_SIZE);
		if (romfs_copyfrom(inode, buf, ROMFS_I(inode)->i_dataoffset+offset, readlen) == readlen) {
			if (readlen < PAGE_SIZE) {
				memset(buf + readlen,0,PAGE_SIZE-readlen);
			}
			SetPageUptodate(page);
			result = 0;
		}
	}
	if (result) {
		memset(buf, 0, PAGE_SIZE);
		SetPageError(page);
	}
	flush_dcache_page(page);

	unlock_page(page);

	kunmap(page);
err_out:
	page_cache_release(page);
	unlock_kernel();

	return result;
}

/* Mapping from our types to the kernel */

static const struct address_space_operations romfs_aops = {
	.readpage = romfs_readpage
};

static const struct file_operations romfs_dir_operations = {
	.read		= generic_read_dir,
	.readdir	= romfs_readdir,
};

static const struct inode_operations romfs_dir_inode_operations = {
	.lookup		= romfs_lookup,
};

static mode_t romfs_modemap[] =
{
	0, S_IFDIR+0644, S_IFREG+0644, S_IFLNK+0777,
	S_IFBLK+0600, S_IFCHR+0600, S_IFSOCK+0644, S_IFIFO+0644
};

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

	ino = i->i_ino & ROMFH_MASK;
	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 = be32_to_cpu(ri.next);
		if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
			break;

		ino = be32_to_cpu(ri.spec) & ROMFH_MASK;
	}

	i->i_nlink = 1;		/* Hard to decide.. */
	i->i_size = be32_to_cpu(ri.size);
	i->i_mtime.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0;
	i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0;
	i->i_uid = i->i_gid = 0;

        /* 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;

        ROMFS_I(i)->i_metasize = ino;
        ROMFS_I(i)->i_dataoffset = ino+(i->i_ino&ROMFH_MASK);

        /* Compute permissions */
        ino = romfs_modemap[nextfh & ROMFH_TYPE];
	/* only "normal" files have ops */
	switch (nextfh & ROMFH_TYPE) {
		case 1:
			i->i_size = ROMFS_I(i)->i_metasize;
			i->i_op = &romfs_dir_inode_operations;
			i->i_fop = &romfs_dir_operations;
			if (nextfh & ROMFH_EXEC)
				ino |= S_IXUGO;
			i->i_mode = ino;
			break;
		case 2:
			i->i_fop = &generic_ro_fops;
			i->i_data.a_ops = &romfs_aops;
			if (nextfh & ROMFH_EXEC)
				ino |= S_IXUGO;
			i->i_mode = ino;
			break;
		case 3:
			i->i_op = &page_symlink_inode_operations;
			i->i_data.a_ops = &romfs_aops;
			i->i_mode = ino | S_IRWXUGO;
			break;
		default:
			/* depending on MBZ for sock/fifos */
			nextfh = be32_to_cpu(ri.spec);
			init_special_inode(i, ino,
					MKDEV(nextfh>>16,nextfh&0xffff));
	}
}

static struct kmem_cache * romfs_inode_cachep;

static struct inode *romfs_alloc_inode(struct super_block *sb)
{
	struct romfs_inode_info *ei;
	ei = kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL);
	if (!ei)
		return NULL;
	return &ei->vfs_inode;
}

static void romfs_destroy_inode(struct inode *inode)
{
	kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
}

static void init_once(struct kmem_cache *cachep, void *foo)
{
	struct romfs_inode_info *ei = foo;

	inode_init_once(&ei->vfs_inode);
}

static int init_inodecache(void)
{
	romfs_inode_cachep = kmem_cache_create("romfs_inode_cache",
					     sizeof(struct romfs_inode_info),
					     0, (SLAB_RECLAIM_ACCOUNT|
						SLAB_MEM_SPREAD),
					     init_once);
	if (romfs_inode_cachep == NULL)
		return -ENOMEM;
	return 0;
}

static void destroy_inodecache(void)
{
	kmem_cache_destroy(romfs_inode_cachep);
}

static int romfs_remount(struct super_block *sb, int *flags, char *data)
{
	*flags |= MS_RDONLY;
	return 0;
}

static const struct super_operations romfs_ops = {
	.alloc_inode	= romfs_alloc_inode,
	.destroy_inode	= romfs_destroy_inode,
	.read_inode	= romfs_read_inode,
	.statfs		= romfs_statfs,
	.remount_fs	= romfs_remount,
};

static int romfs_get_sb(struct file_system_type *fs_type,
	int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
	return get_sb_bdev(fs_type, flags, dev_name, data, romfs_fill_super,
			   mnt);
}

static struct file_system_type romfs_fs_type = {
	.owner		= THIS_MODULE,
	.name		= "romfs",
	.get_sb		= romfs_get_sb,
	.kill_sb	= kill_block_super,
	.fs_flags	= FS_REQUIRES_DEV,
};

static int __init init_romfs_fs(void)
{
	int err = init_inodecache();
	if (err)
		goto out1;
        err = register_filesystem(&romfs_fs_type);
	if (err)
		goto out;
	return 0;
out:
	destroy_inodecache();
out1:
	return err;
}

static void __exit exit_romfs_fs(void)
{
	unregister_filesystem(&romfs_fs_type);
	destroy_inodecache();
}

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

module_init(init_romfs_fs)
module_exit(exit_romfs_fs)
MODULE_LICENSE("GPL");