From: Theodore Ts'o Subject: Re: Is ext2 freezable? Date: Thu, 18 Sep 2014 15:17:36 -0400 Message-ID: <20140918191736.GC19520@thunk.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "linux-ext4@vger.kernel.org" To: Dexuan Cui Return-path: Received: from imap.thunk.org ([74.207.234.97]:36189 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751125AbaIRTRk (ORCPT ); Thu, 18 Sep 2014 15:17:40 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: On Thu, Sep 18, 2014 at 06:46:21AM +0000, Dexuan Cui wrote: > > I've got the answer: > ext2.ko itself does support fsfreeze, but typical linux distros don't supply > ext2.ko at all now -- instead, they usually supply ext3.ko and have ext4 builtin. > > So when I mount an ext2 partition, actually the kernel is registering the ext4 > driver as an ext2 driver and in this case the ext2's s_op->freeze_fs is NULL -- > but, why did ext4 choose this behavior for ext2? It wasn't a deliberate design choice. It was just that when no-journal mode was added to ext4, freeeze support was never implemented, and up until now, no one had asked for it. We can add it to ext4; thanks for calling it to our attention. Cheers, - Ted