From: Theodore Ts'o Subject: Re: [PATCH 0/3] Remove ext3 filesystem driver Date: Wed, 15 Jul 2015 19:23:46 -0400 Message-ID: <20150715232346.GD18400@thunk.org> References: <1436955987-7305-1-git-send-email-jack@suse.com> <20150715141836.GA18400@thunk.org> <55A676BF.8020903@infradead.org> <55A67790.80802@infradead.org> <55A6780E.2040702@redhat.com> <55A67A57.8010502@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Eric Sandeen , Randy Dunlap , Jan Kara , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, LKML , Andrew Morton , Andreas Dilger , Jens Axboe To: Austin S Hemmelgarn Return-path: Content-Disposition: inline In-Reply-To: <55A67A57.8010502@gmail.com> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Wed, Jul 15, 2015 at 11:20:55AM -0400, Austin S Hemmelgarn wrote: > > There really isn't much of a clear distinction between ext3 and ext4 (at > least from an end user standpoint), other than the fact that there are some > options that only the ext4 driver understands (like extent based > allocation). Yeah, the main reason why we did the ext3 -> ext4 fork was that adding 64-bit numbers required major surgery, and we didn't want to break a lot of production users who were using ext3. But from a file system format perspective, ext2, ext3, and ext4 are the same logical file system. There are just multiple different implementations, which all support slightly different sets of file system features: * Linux's ext2 * Linux's ext3 * Linux's ext4 * Hurd's ext2 * *BSD's ext2 * Grub's ext2/3/4 The last three implementations are in fact independent ones created from scratch. :-) Fortunately we use the same file system support code, e2fsprogs, for all of them, which is good since it has a very extensive set of regression test sets for our fsck program, and we've continued adding to it as we add new file system features. - Ted