path: root/fs/hostfs/hostfs_kern.c

/*
 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Licensed under the GPL
 *
 * Ported the filesystem routines to 2.5.
 * 2003-02-10 Petr Baudis <pasky@ucw.cz>
 */

#include <linux/fs.h>
#include <linux/magic.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/statfs.h>
#include <linux/slab.h>
#include <linux/seq_file.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include "hostfs.h"
#include <init.h>
#include <kern.h>

struct hostfs_inode_info {
	int fd;
	fmode_t mode;
	struct inode vfs_inode;
	struct mutex open_mutex;
};

static inline struct hostfs_inode_info *HOSTFS_I(struct inode *inode)
{
	return list_entry(inode, struct hostfs_inode_info, vfs_inode);
}

#define FILE_HOSTFS_I(file) HOSTFS_I(file_inode(file))

/* Changed in hostfs_args before the kernel starts running */
static char *root_ino = "";
static int append = 0;

static const struct inode_operations hostfs_iops;
static const struct inode_operations hostfs_dir_iops;
static const struct inode_operations hostfs_link_iops;

#ifndef MODULE
static int __init hostfs_args(char *options, int *add)
{
	char *ptr;

	ptr = strchr(options, ',');
	if (ptr != NULL)
		*ptr++ = '\0';
	if (*options != '\0')
		root_ino = options;

	options = ptr;
	while (options) {
		ptr = strchr(options, ',');
		if (ptr != NULL)
			*ptr++ = '\0';
		if (*options != '\0') {
			if (!strcmp(options, "append"))
				append = 1;
			else printf("hostfs_args - unsupported option - %s\n",
				    options);
		}
		options = ptr;
	}
	return 0;
}

__uml_setup("hostfs=", hostfs_args,
"hostfs=<root dir>,<flags>,...\n"
"    This is used to set hostfs parameters.  The root directory argument\n"
"    is used to confine all hostfs mounts to within the specified directory\n"
"    tree on the host.  If this isn't specified, then a user inside UML can\n"
"    mount anything on the host that's accessible to the user that's running\n"
"    it.\n"
"    The only flag currently supported is 'append', which specifies that all\n"
"    files opened by hostfs will be opened in append mode.\n\n"
);
#endif

static char *__dentry_name(struct dentry *dentry, char *name)
{
	char *p = dentry_path_raw(dentry, name, PATH_MAX);
	char *root;
	size_t len;

	root = dentry->d_sb->s_fs_info;
	len = strlen(root);
	if (IS_ERR(p)) {
		__putname(name);
		return NULL;
	}

	/*
	 * This function relies on the fact that dentry_path_raw() will place
	 * the path name at the end of the provided buffer.
	 */
	BUG_ON(p + strlen(p) + 1 != name + PATH_MAX);

	strlcpy(name, root, PATH_MAX);
	if (len > p - name) {
		__putname(name);
		return NULL;
	}

	if (p > name + len)
		strcpy(name + len, p);

	return name;
}

static char *dentry_name(struct dentry *dentry)
{
	char *name = __getname();
	if (!name)
		return NULL;

	return __dentry_name(dentry, name);
}

static char *inode_name(struct inode *ino)
{
	struct dentry *dentry;
	char *name;

	dentry = d_find_alias(ino);
	if (!dentry)
		return NULL;

	name = dentry_name(dentry);

	dput(dentry);

	return name;
}

static char *follow_link(char *link)
{
	int len, n;
	char *name, *resolved, *end;

	name = __getname();
	if (!name) {
		n = -ENOMEM;
		goto out_free;
	}

	n = hostfs_do_readlink(link, name, PATH_MAX);
	if (n < 0)
		goto out_free;
	else if (n == PATH_MAX) {
		n = -E2BIG;
		goto out_free;
	}

	if (*name == '/')
		return name;

	end = strrchr(link, '/');
	if (end == NULL)
		return name;

	*(end + 1) = '\0';
	len = strlen(link) + strlen(name) + 1;

	resolved = kmalloc(len, GFP_KERNEL);
	if (resolved == NULL) {
		n = -ENOMEM;
		goto out_free;
	}

	sprintf(resolved, "%s%s", link, name);
	__putname(name);
	kfree(link);
	return resolved;

 out_free:
	__putname(name);
	return ERR_PTR(n);
}

static struct inode *hostfs_iget(struct super_block *sb)
{
	struct inode *inode = new_inode(sb);
	if (!inode)
		return ERR_PTR(-ENOMEM);
	return inode;
}

static int hostfs_statfs(struct dentry *dentry, struct kstatfs *sf)
{
	/*
	 * do_statfs uses struct statfs64 internally, but the linux kernel
	 * struct statfs still has 32-bit versions for most of these fields,
	 * so we convert them here
	 */
	int err;
	long long f_blocks;
	long long f_bfree;
	long long f_bavail;
	long long f_files;
	long long f_ffree;

	err =