C++ IS_APPEND函数代码示例

int sys_fcntl(unsigned int fd, unsigned int cmd, unsigned int arg)
{
    register struct file *filp;
    register struct file_struct *fils = &current->files;
    int result;

    if (fd >= NR_OPEN || !(filp = fils->fd[fd])) return -EBADF;

    switch (cmd) {
    case F_DUPFD:
	result = dupfd(fd, arg);
	break;
    case F_GETFD:
	result = test_bit(fd, &fils->close_on_exec);
	break;
    case F_SETFD:
	if (arg & 1)
	    set_bit(fd, &fils->close_on_exec);
	else
	    clear_bit(fd, &fils->close_on_exec);
	result = 0;
	break;
    case F_GETFL:
	result = (int) filp->f_flags;
	break;
    case F_SETFL:
	/*
	 * In the case of an append-only file, O_APPEND
	 * cannot be cleared
	 */
	result = -EPERM;
	if (!IS_APPEND(filp->f_inode) || (arg & O_APPEND)) {
	    filp->f_flags &= ~(O_APPEND | O_NONBLOCK);
	    filp->f_flags |= arg & (O_APPEND | O_NONBLOCK);
	    result = 0;
	}
	break;
    default:
	result = -EINVAL;
	break;
    }

    return result;
}

static long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
{
	struct inode * inode;
	struct dentry *dentry;
	struct file * file;
	int error;

	error = -EINVAL;
	if (length < 0)
		goto out;
	error = -EBADF;
	file = fget(fd);
	if (!file)
		goto out;

	/* explicitly opened as large or we are on 64-bit box */
	if (file->f_flags & O_LARGEFILE)
		small = 0;

	dentry = file->f_path.dentry;
	inode = dentry->d_inode;
	error = -EINVAL;
	if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
		goto out_putf;

	error = -EINVAL;
	/* Cannot ftruncate over 2^31 bytes without large file support */
	if (small && length > MAX_NON_LFS)
		goto out_putf;

	error = -EPERM;
	if (IS_APPEND(inode))
		goto out_putf;

	error = locks_verify_truncate(inode, file, length);
	if (!error)
		error = security_path_truncate(&file->f_path);
	if (!error)
		error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, file);
out_putf:
	fput(file);
out:
	return error;
}

static void call_notify_change(void *args)
{
	struct notify_change_args *a = args;
	struct inode *h_inode;

	h_inode = d_inode(a->path->dentry);
	IMustLock(h_inode);

	*a->errp = -EPERM;
	if (!IS_IMMUTABLE(h_inode) && !IS_APPEND(h_inode)) {
		lockdep_off();
		*a->errp = notify_change(a->path->dentry, a->ia,
					 a->delegated_inode);
		lockdep_on();
		if (!*a->errp)
			vfsub_update_h_iattr(a->path, /*did*/NULL); /*ignore*/
	}
	AuTraceErr(*a->errp);
}

STATIC int
xfs_fssetdm_by_handle(
	struct file		*parfilp,
	void			__user *arg)
{
	int			error;
	struct fsdmidata	fsd;
	xfs_fsop_setdm_handlereq_t dmhreq;
	struct dentry		*dentry;

	if (!capable(CAP_MKNOD))
		return -EPERM;
	if (copy_from_user(&dmhreq, arg, sizeof(xfs_fsop_setdm_handlereq_t)))
		return -EFAULT;

	error = mnt_want_write_file(parfilp);
	if (error)
		return error;

	dentry = xfs_handlereq_to_dentry(parfilp, &dmhreq.hreq);
	if (IS_ERR(dentry)) {
		mnt_drop_write_file(parfilp);
		return PTR_ERR(dentry);
	}

	if (IS_IMMUTABLE(d_inode(dentry)) || IS_APPEND(d_inode(dentry))) {
		error = -EPERM;
		goto out;
	}

	if (copy_from_user(&fsd, dmhreq.data, sizeof(fsd))) {
		error = -EFAULT;
		goto out;
	}

	error = xfs_set_dmattrs(XFS_I(d_inode(dentry)), fsd.fsd_dmevmask,
				 fsd.fsd_dmstate);

 out:
	mnt_drop_write_file(parfilp);
	dput(dentry);
	return error;
}

/*
 * Check permissions for extended attribute access.  This is a bit complicated
 * because different namespaces have very different rules.
 */
static int
xattr_permission(struct inode *inode, const char *name, int mask)
{
	/*
	 * We can never set or remove an extended attribute on a read-only
	 * filesystem  or on an immutable / append-only inode.
	 */
	if (mask & MAY_WRITE) {
		if (IS_RDONLY(inode))
			return -EROFS;
		if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
			return -EPERM;
	}

	/*
	 * No restriction for security.* and system.* from the VFS.  Decision
	 * on these is left to the underlying filesystem / security module.
	 */
	if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
	    !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
		return 0;

	/*
	 * The trusted.* namespace can only be accessed by a privileged user.
	 */
	if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN))
		return (capable(CAP_SYS_ADMIN) ? 0 : -EPERM);

	/* In user.* namespace, only regular files and directories can have
	 * extended attributes. For sticky directories, only the owner and
	 * privileged user can write attributes.
	 */
	if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
		if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
			return -EPERM;
		if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
		    (mask & MAY_WRITE) && (current->fsuid != inode->i_uid) &&
		    !capable(CAP_FOWNER))
			return -EPERM;
	}

	return permission(inode, mask, NULL);
}

asmlinkage int sys_truncate(const char * path, unsigned long length)
{
	struct inode * inode;
	int error;

	error = namei(path,&inode);
	if (error)
		return error;

	error = -EACCES;
	if (S_ISDIR(inode->i_mode))
		goto out;

	error = permission(inode,MAY_WRITE);
	if (error)
		goto out;

	error = -EROFS;
	if (IS_RDONLY(inode))
		goto out;

	error = -EPERM;
	if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
		goto out;

	error = get_write_access(inode);
	if (error)
		goto out;

	error = locks_verify_area(FLOCK_VERIFY_WRITE, inode, NULL,
				  length < inode->i_size ? length : inode->i_size,
				  abs(inode->i_size - length));
	if (!error) {
		if (inode->i_sb && inode->i_sb->dq_op)
			inode->i_sb->dq_op->initialize(inode, -1);
		error = do_truncate(inode, length);
	}
	put_write_access(inode);
out:
	iput(inode);
	return error;
}

STATIC int
xfs_fssetdm_by_handle(
	xfs_mount_t		*mp,
	void			__user *arg,
	struct file		*parfilp,
	struct inode		*parinode)
{
	int			error;
	struct fsdmidata	fsd;
	xfs_fsop_setdm_handlereq_t dmhreq;
	struct inode		*inode;
	bhv_desc_t		*bdp;
	vnode_t			*vp;

	if (!capable(CAP_MKNOD))
		return -XFS_ERROR(EPERM);
	if (copy_from_user(&dmhreq, arg, sizeof(xfs_fsop_setdm_handlereq_t)))
		return -XFS_ERROR(EFAULT);

	error = xfs_vget_fsop_handlereq(mp, parinode, &dmhreq.hreq, &vp, &inode);
	if (error)
		return -error;

	if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) {
		VN_RELE(vp);
		return -XFS_ERROR(EPERM);
	}

	if (copy_from_user(&fsd, dmhreq.data, sizeof(fsd))) {
		VN_RELE(vp);
		return -XFS_ERROR(EFAULT);
	}

	bdp = bhv_base_unlocked(VN_BHV_HEAD(vp));
	error = xfs_set_dmattrs(bdp, fsd.fsd_dmevmask, fsd.fsd_dmstate, NULL);

	VN_RELE(vp);
	if (error)
		return -error;
	return 0;
}

/* Based on sys_fchmod() from linux 2.6.21 (mostly unchanged since 2.4.0). */
int cr_filp_chmod(struct file *filp, mode_t mode) {
    struct iattr newattrs;
    struct dentry *dentry = filp->f_dentry;
    struct inode *inode = dentry->d_inode;
    int retval;

    retval = -EROFS;
    if (IS_RDONLY(inode)) goto out;
    retval = -EPERM;
    if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) goto out;

    cr_inode_lock(inode);
    newattrs.ia_mode = (mode == (mode_t)-1) ? inode->i_mode
					    : ((mode & S_IALLUGO)|(inode->i_mode & ~S_IALLUGO));
    newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
    retval = cr_notify_change(dentry, filp->f_vfsmnt, &newattrs);
    cr_inode_unlock(inode);

out:
    return retval;
}

/** Change size of an object referenced by inode
 */
void pvfs2_truncate(struct inode *inode)
{
    loff_t orig_size = pvfs2_i_size_read(inode);

    if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
        return;
    gossip_debug(GOSSIP_INODE_DEBUG, "pvfs2: pvfs2_truncate called on inode %llu "
                "with size %ld\n", llu(get_handle_from_ino(inode)), (long) orig_size);

    /* successful truncate when size changes also requires mtime updates 
     * although the mtime updates are propagated lazily!
     */
    if (pvfs2_truncate_inode(inode, inode->i_size) == 0
            && (orig_size != pvfs2_i_size_read(inode)))
    {
        pvfs2_inode_t *pvfs2_inode = PVFS2_I(inode);
        SetMtimeFlag(pvfs2_inode);
        inode->i_mtime = CURRENT_TIME;
        mark_inode_dirty_sync(inode);
    }
}

int mext_check_arguments(struct inode *orig_inode,
		     struct inode *donor_inode, __u64 orig_start,
		     __u64 donor_start, __u64 *len)
{

	unsigned int blkbits = orig_inode->i_blkbits;
	unsigned int blocksize = 1 << blkbits;

#ifdef __PATCH__
	if (IS_IMMUTABLE(donor_inode) || IS_APPEND(donor_inode))
		return -EPERM;
#endif

	if ((!orig_inode->i_size) || (!donor_inode->i_size))
		return -EINVAL;

	if (!*len)
		return -EINVAL;

	return 0;
}

asmlinkage int sys_fchmod(unsigned int fd, mode_t mode)
{
	struct inode * inode;
	struct file * file;
	struct iattr newattrs;

	if (fd >= NR_OPEN || !(file = current->files->fd[fd]))
		return -EBADF;
	if (!(inode = file->f_inode))
		return -ENOENT;
	if (IS_RDONLY(inode))
		return -EROFS;
	if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
		return -EPERM;
	if (mode == (mode_t) -1)
		mode = inode->i_mode;
	newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
	newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
	inode->i_dirt = 1;
	return notify_change(inode, &newattrs);
}

asmlinkage int sys_ftruncate(unsigned int fd, unsigned long length)
{
	struct inode * inode;
	struct file * file;
	int error;

	if (fd >= NR_OPEN || !(file = current->files->fd[fd]))
		return -EBADF;
	if (!(inode = file->f_inode))
		return -ENOENT;
	if (S_ISDIR(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
		return -EACCES;
	if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
		return -EPERM;
	error = locks_verify_area(FLOCK_VERIFY_WRITE, inode, file,
				  length < inode->i_size ? length : inode->i_size,
				  abs(inode->i_size - length));
	if (!error)
		error = do_truncate(inode, length);
	return error;
}

int
xfs_attrmulti_attr_set(
	struct inode		*inode,
	unsigned char		*name,
	const unsigned char	__user *ubuf,
	__uint32_t		len,
	__uint32_t		flags)
{
	unsigned char		*kbuf;

	if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
		return -EPERM;
	if (len > XATTR_SIZE_MAX)
		return -EINVAL;

	kbuf = memdup_user(ubuf, len);
	if (IS_ERR(kbuf))
		return PTR_ERR(kbuf);

	return xfs_attr_set(XFS_I(inode), name, kbuf, len, flags);
}

asmlinkage long sys_fchmod(unsigned int fd, mode_t mode)
{
    struct inode * inode;
    struct dentry * dentry;
    struct file * file;
    int err = -EBADF;
    struct iattr newattrs;

    file = fget(fd);
    if (!file)
        goto out;

    dentry = file->f_path.dentry;
    inode = dentry->d_inode;

    audit_inode(NULL, dentry);

    err = mnt_want_write(file->f_path.mnt);
    if (err)
        goto out_putf;
    err = -EPERM;
    if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
        goto out_drop_write;
    mutex_lock(&inode->i_mutex);
    if (mode == (mode_t) -1)
        mode = inode->i_mode;
    newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
    newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
    err = notify_change(dentry, &newattrs);
    mutex_unlock(&inode->i_mutex);

out_drop_write:
    mnt_drop_write(file->f_path.mnt);
out_putf:
    fput(file);
out:
    return err;
}

STATIC int
xfs_fssetdm_by_handle(
	xfs_mount_t		*mp,
	void			__user *arg,
	struct inode		*parinode)
{
	int			error;
	struct fsdmidata	fsd;
	xfs_fsop_setdm_handlereq_t dmhreq;
	struct inode		*inode;

	if (!capable(CAP_MKNOD))
		return -XFS_ERROR(EPERM);
	if (copy_from_user(&dmhreq, arg, sizeof(xfs_fsop_setdm_handlereq_t)))
		return -XFS_ERROR(EFAULT);

	error = xfs_vget_fsop_handlereq(mp, parinode, &dmhreq.hreq, &inode);
	if (error)
		return -error;

	if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) {
		error = -XFS_ERROR(EPERM);
		goto out;
	}

	if (copy_from_user(&fsd, dmhreq.data, sizeof(fsd))) {
		error = -XFS_ERROR(EFAULT);
		goto out;
	}

	error = -xfs_set_dmattrs(XFS_I(inode), fsd.fsd_dmevmask,
				 fsd.fsd_dmstate);

 out:
	iput(inode);
	return error;
}