From: Eric Sandeen Subject: Re: [PATCH] do not set extents feature from the kernel Date: Mon, 07 Jul 2008 21:25:36 -0500 Message-ID: <4872D020.5000309@redhat.com> References: <48727954.1080406@redhat.com> <6149e97b0807071923t62379bf0qc682c6cbc15e1380@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: ext4 development To: Peng tao Return-path: Received: from mx1.redhat.com ([66.187.233.31]:56300 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755421AbYGHCZt (ORCPT ); Mon, 7 Jul 2008 22:25:49 -0400 In-Reply-To: <6149e97b0807071923t62379bf0qc682c6cbc15e1380@mail.gmail.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: Peng tao wrote: > Hi, Eric > > On Tue, Jul 8, 2008 at 4:15 AM, Eric Sandeen wrote: >> 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 mean no more migration from ext3 to ext4? I think it just means you need to tune2fs -O extents before you can mount as ext4 *with* extents. .... which is, I guess, a bit of a convoluted story, but consistent with "don't surprise users by setting incompat flags behind their back" -Eric >> 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); >> >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> > > >