From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755869Ab3BRNLW (ORCPT ); Mon, 18 Feb 2013 08:11:22 -0500 Received: from fn.samba.org ([216.83.154.106]:43790 "EHLO mail.samba.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755036Ab3BRNLV (ORCPT ); Mon, 18 Feb 2013 08:11:21 -0500 Message-ID: <1361193074.5565.87.camel@jesse> Subject: Re: Read support for fat_fallocate()? (was [v2] fat: editions to support fat_fallocate()) From: Andrew Bartlett To: OGAWA Hirofumi Cc: Namjae Jeon , linux-kernel@vger.kernel.org, Ravishankar N , Amit Sahrawat , Nam-Jae Jeon , Ravishankar N , Amit Sahrawat Date: Tue, 19 Feb 2013 00:11:14 +1100 In-Reply-To: <87fw0t26qu.fsf@devron.myhome.or.jp> References: <1350138661-2454-1-git-send-email-linkinjeon@gmail.com> <1360810114.1727.306.camel@jesse> <1360825669.1727.337.camel@jesse> <1360900178.1727.393.camel@jesse> <87fw0t26qu.fsf@devron.myhome.or.jp> Organization: Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.4.4 (3.4.4-2.fc17) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2013-02-18 at 20:36 +0900, OGAWA Hirofumi wrote: > Andrew Bartlett writes: > > Or, if we cannot make any changes to the on-disk format, what about > > keeping such a database in memory, allocating some of the existing free > > list to files that have had fallocate() called on them? (Naturally, > > this makes it non-persistent, and instead more of a 'hint', but could at > > least solve our mutual performance issues). > > [...] > > Hm. My concerns are compatibility and reliability. Although We can > change on-disk format if need, but I don't think it can be compatible > and reliable. If so, who wants to use it? I feel there is no reason to > use FAT if there is no compatible. > > Well, anyway, possible solution would be, we can pre-allocate physical > blocks via fallocate(2) or something, but discard pre-allocated blocks > at ->release() (or before unmount at least). This way would have > compatibility (no on-disk change over unmount) and possible breakage > would be same with normal extend write patterns on kernel crash > (i.e. Windows or fsck will truncate after i_size). That would certainly give me what the Samba NAS with USB FAT disk use case needs. Thanks, Andrew Bartlett -- Andrew Bartlett http://samba.org/~abartlet/ Authentication Developer, Samba Team http://samba.org