get rid of s_files and files_lock

The only thing we need it for is alt-sysrq-r (emergency remount r/o)
and these days we can do just as well without going through the
list of files.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
static int chown_common(struct path *path, uid_t user, gid_t group)
{
	struct inode *inode = path->dentry->d_inode;
	int error;
	struct iattr newattrs;
	kuid_t uid;
	kgid_t gid;

	uid = make_kuid(current_user_ns(), user);
	gid = make_kgid(current_user_ns(), group);

	newattrs.ia_valid =  ATTR_CTIME;
	if (user != (uid_t) -1) {
		if (!uid_valid(uid))
			return -EINVAL;
		newattrs.ia_valid |= ATTR_UID;
		newattrs.ia_uid = uid;
	}
	if (group != (gid_t) -1) {
		if (!gid_valid(gid))
			return -EINVAL;
		newattrs.ia_valid |= ATTR_GID;
		newattrs.ia_gid = gid;
	}
	if (!S_ISDIR(inode->i_mode))
		newattrs.ia_valid |=
			ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
	mutex_lock(&inode->i_mutex);
	error = security_path_chown(path, uid, gid);
	if (!error)
		error = notify_change(path->dentry, &newattrs);
	mutex_unlock(&inode->i_mutex);

	return error;
}

static int chown_common(struct path *path, uid_t user, gid_t group)
{
	struct inode *inode = path->dentry->d_inode;
	int error;
	struct iattr newattrs;
	kuid_t uid;
	kgid_t gid;

	uid = make_kuid(current_user_ns(), user);
	gid = make_kgid(current_user_ns(), group);

	newattrs.ia_valid =  ATTR_CTIME;
	if (user != (uid_t) -1) {
		if (!uid_valid(uid))
			return -EINVAL;
		newattrs.ia_valid |= ATTR_UID;
		newattrs.ia_uid = uid;
	}
	if (group != (gid_t) -1) {
		if (!gid_valid(gid))
			return -EINVAL;
		newattrs.ia_valid |= ATTR_GID;
		newattrs.ia_gid = gid;
	}
	if (!S_ISDIR(inode->i_mode))
		newattrs.ia_valid |=
			ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
	mutex_lock(&inode->i_mutex);
	error = security_path_chown(path, uid, gid);
	if (!error)
		error = notify_change(path->dentry, &newattrs);
	mutex_unlock(&inode->i_mutex);

	return error;
}
