From: Arnd Bergmann Subject: Re: [PATCH 0/3] Extended file stat functions [ver #2] Date: Wed, 30 Jun 2010 15:31:39 +0200 Message-ID: <201006301531.39365.arnd@arndb.de> References: <52423201-3DF9-4045-8E8B-FAA915053D56@dilger.ca> <26505.1277899544@redhat.com> <20100630121127.GA22713@infradead.org> Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Cc: David Howells , Andreas Dilger , viro@zeniv.linux.org.uk, smfrench@gmail.com, jlayton@redhat.com, mcao@us.ibm.com, aneesh.kumar@linux.vnet.ibm.com, linux-cifs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, samba-technical@lists.samba.org, sjayaraman@suse.de, linux-ext4@vger.kernel.org To: Christoph Hellwig Return-path: Received: from moutng.kundenserver.de ([212.227.17.8]:62562 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752495Ab0F3Nbt (ORCPT ); Wed, 30 Jun 2010 09:31:49 -0400 In-Reply-To: <20100630121127.GA22713@infradead.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Wednesday 30 June 2010, Christoph Hellwig wrote: > The cost of adding a syscall is much smaller Ack. No need for different struct layout version since we can add another stat syscall every ten years. > So adding a few fields of padding at the end for new members is fine, > but doing overkill of versioning including queries for supported > versions doesn't. The ability to request and return a subset of the fields seems useful regardless and it can be used to avoid the need for this kind of padding. A sufficient amount of padding wouldn't be too bad either, but I guess we should not have both the padding _and_ the option for extending the structure after the padding. With the padding, the 'size' argument can go away, though I'd argue that even without the padding we can safely add extra fixed-length fields when needed and not need a size argument. Arnd