From: Eric Sandeen Subject: [PATCH] do not set extents feature from the kernel Date: Mon, 07 Jul 2008 15:15:16 -0500 Message-ID: <48727954.1080406@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit To: ext4 development Return-path: Received: from mx1.redhat.com ([66.187.233.31]:35010 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755392AbYGGUP0 (ORCPT ); Mon, 7 Jul 2008 16:15:26 -0400 Received: from int-mx1.corp.redhat.com (int-mx1.corp.redhat.com [172.16.52.254]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id m67KFPh7023315 for ; Mon, 7 Jul 2008 16:15:25 -0400 Received: from pobox-2.corp.redhat.com (pobox-2.corp.redhat.com [10.11.255.15]) by int-mx1.corp.redhat.com (8.13.1/8.13.1) with ESMTP id m67KFPZS007798 for ; Mon, 7 Jul 2008 16:15:25 -0400 Received: from liberator.sandeen.net (sebastian-int.corp.redhat.com [172.16.52.221]) by pobox-2.corp.redhat.com (8.13.1/8.13.1) with ESMTP id m67KFNnI003008 for ; Mon, 7 Jul 2008 16:15:24 -0400 Sender: linux-ext4-owner@vger.kernel.org List-ID: We've talked for a while about getting rid of any feature- setting from the kernel; this gets rid of the code which would set the INCOMPAT_EXTENTS flag on the first file write when mounted as ext4[dev]. With this patch, if the extents feature is not already set on disk, then mounting as ext4 will fall back to noextents with a warning, and if -o extents is explicitly requested, the mount will fail, also with warning. Does this seem like a decent approach? Signed-off-by: Eric Sandeen --- Index: linux-2.6/fs/ext4/ialloc.c =================================================================== --- linux-2.6.orig/fs/ext4/ialloc.c 2008-07-07 10:22:00.000000000 -0500 +++ linux-2.6/fs/ext4/ialloc.c 2008-07-07 12:07:02.133292077 -0500 @@ -740,14 +740,10 @@ got: goto fail_free_drop; if (test_opt(sb, EXTENTS)) { - /* set extent flag only for diretory, file and normal symlink*/ + /* set extent flag only for directory, file and normal symlink*/ if (S_ISDIR(mode) || S_ISREG(mode) || S_ISLNK(mode)) { EXT4_I(inode)->i_flags |= EXT4_EXTENTS_FL; ext4_ext_tree_init(handle, inode); - err = ext4_update_incompat_feature(handle, sb, - EXT4_FEATURE_INCOMPAT_EXTENTS); - if (err) - goto fail_free_drop; } } Index: linux-2.6/fs/ext4/super.c =================================================================== --- linux-2.6.orig/fs/ext4/super.c 2008-07-07 10:22:19.000000000 -0500 +++ linux-2.6/fs/ext4/super.c 2008-07-07 14:08:43.684291817 -0500 @@ -1309,6 +1309,13 @@ set_qf_format: clear_opt(sbi->s_mount_opt, NOBH); break; case Opt_extents: + if (!EXT4_HAS_INCOMPAT_FEATURE(sb, + EXT4_FEATURE_INCOMPAT_EXTENTS)) { + ext4_warning(sb, __func__, + "extents feature not enabled " + "on this filesystem, use tune2fs\n"); + return 0; + } set_opt (sbi->s_mount_opt, EXTENTS); break; case Opt_noextents: @@ -1919,12 +1926,18 @@ static int ext4_fill_super (struct super /* * turn on extents feature by default in ext4 filesystem - * User -o noextents to turn it off + * only if feature flag already set by mkfs or tune2fs. + * Use -o noextents to turn it off */ - set_opt(sbi->s_mount_opt, EXTENTS); + if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_EXTENTS)) + set_opt(sbi->s_mount_opt, EXTENTS); + else + ext4_warning(sb, __func__, + "extents feature not enabled on this filesystem, " + "use tune2fs.\n"); /* - * turn on mballoc feature by default in ext4 filesystem - * User -o nomballoc to turn it off + * turn on mballoc code by default in ext4 filesystem + * Use -o nomballoc to turn it off */ set_opt(sbi->s_mount_opt, MBALLOC);