From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?ISO-8859-15?Q?Luk=E1=A8_Czerner?= Subject: Re: [PATCH] mke2fs: Disallow bigalloc with with bs < 4096 Date: Wed, 3 Apr 2013 16:47:55 +0200 (CEST) Message-ID: References: <1364997099-22590-1-git-send-email-lczerner@redhat.com> <20130403143554.GA13668@thunk.org> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: Lukas Czerner , linux-ext4@vger.kernel.org To: "Theodore Ts'o" Return-path: Received: from mx1.redhat.com ([209.132.183.28]:54546 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932111Ab3DCOsA (ORCPT ); Wed, 3 Apr 2013 10:48:00 -0400 In-Reply-To: <20130403143554.GA13668@thunk.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Wed, 3 Apr 2013, Theodore Ts'o wrote: > Date: Wed, 3 Apr 2013 10:35:54 -0400 > From: Theodore Ts'o > To: Lukas Czerner > Cc: linux-ext4@vger.kernel.org > Subject: Re: [PATCH] mke2fs: Disallow bigalloc with with bs < 4096 > > On Wed, Apr 03, 2013 at 03:51:39PM +0200, Lukas Czerner wrote: > > Currently there is nothing preventing user to create file system with > > bigalloc feature enabled and block size smaller than 4096 Bytes. However > > such combination does not make much sense at all because the whole point > > of bigalloc is to have bigger allocation units. > > > > This patch disallow such combination. > > This makes sense by default but I do see a point in allowing it for > testing purposes --- specifically, it allows us to verify that > bigalloc works on architectures such as PowerPC and Itanium where page > size is greater than the 4k block size. So maybe a developer mode set > via mke2fs.conf? Yes, I though about that and I wanted to know what the general opinion is. I'll prepare the patch which makes this tunable, but restricted by default. > > Another option would be to enforce that we only support bigalloc file > systems where the blocksize == pagesize, but that means we wouldn't be > able to mount 4k bigalloc file systems on architectures with a 8k or > 16k page size. Unfortunately we can't do that for the reasons you mentioned. Thanks! -Lukas > > - Ted >