From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp1040.oracle.com ([156.151.31.81]:22757 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752958Ab3D3GMe (ORCPT ); Tue, 30 Apr 2013 02:12:34 -0400 Message-ID: <517F6158.5000405@oracle.com> Date: Tue, 30 Apr 2013 14:14:48 +0800 From: Anand Jain MIME-Version: 1.0 To: Stefan Behrens CC: linux-btrfs Subject: Re: device delete to get errors from the kernel References: <51623C0C.4060709@oracle.com> <517A4B44.5060608@oracle.com> <517A5C27.3090803@giantdisaster.de> In-Reply-To: <517A5C27.3090803@giantdisaster.de> Content-Type: text/plain; charset=UTF-8; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: Thanks Stefan. :: > About the issue you mentioned, that you need to change the kernel and > the user mode at the same time: > You can keep it compatible. Just do not delete the old kernel interface. > The user mode program could try the new interface first, and if it > fails, fall back to the old interface. You can use the same ioctl number > for both ways if you change the length of the ioctl parameter. Here there won't be a definite failure as such, kernel could send or read garbage if the old and new structures don't match. The problem with most of the ioctl api structures are they don't (already) share the struct len. So it won't be possible to know which version of the structure is being used by the other party? Anand