* Mounting Ext3 with Ext4
@ 2009-05-20 23:24 Matt LaPlante
2009-05-21 1:17 ` Eric Sandeen
0 siblings, 1 reply; 6+ messages in thread
From: Matt LaPlante @ 2009-05-20 23:24 UTC (permalink / raw)
To: linux-ext4
According to the Ext4 howto
(http://ext4.wiki.kernel.org/index.php/Ext4_Howto#Converting_an_ext3_filesystem_to_ext4),
"It is possible to mount both ext3 (and ext2, in kernels 2.6.28 and
later) filesystems directly using the ext4 filesystem driver." So
this means, if I'm reading it correctly, that a kernel built with ext4
support should be able to mount and manage ext[234] filesystems. Is
that correct? If so, are there any limitations on this support?
I'm running Ubuntu Jaunty with some custom-built 2.6.29.4 kernels and
grub2. I seem to have no problem booting from ext4 disks, so the ext4
support is definitely there and functioning. I had hoped the ext3
support meant I could build the kernel with ext4 only and carry on as
usual with my ext3 partitions. Unfortunately doing so causes the ext3
partitions to fail to boot. So...
booting ext3 with ext3 in the kernel=fine
booting ext4 with ext4 in the kernel=fine
booting ext3 with ext4 (only) in the kernel=not fine
Is this a problem or was it never intended to work?
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Mounting Ext3 with Ext4
2009-05-20 23:24 Mounting Ext3 with Ext4 Matt LaPlante
@ 2009-05-21 1:17 ` Eric Sandeen
2009-05-21 1:28 ` Matt LaPlante
0 siblings, 1 reply; 6+ messages in thread
From: Eric Sandeen @ 2009-05-21 1:17 UTC (permalink / raw)
To: Matt LaPlante; +Cc: linux-ext4
Matt LaPlante wrote:
> According to the Ext4 howto
> (http://ext4.wiki.kernel.org/index.php/Ext4_Howto#Converting_an_ext3_filesystem_to_ext4),
> "It is possible to mount both ext3 (and ext2, in kernels 2.6.28 and
> later) filesystems directly using the ext4 filesystem driver." So
> this means, if I'm reading it correctly, that a kernel built with ext4
> support should be able to mount and manage ext[234] filesystems. Is
> that correct? If so, are there any limitations on this support?
>
> I'm running Ubuntu Jaunty with some custom-built 2.6.29.4 kernels and
> grub2. I seem to have no problem booting from ext4 disks, so the ext4
> support is definitely there and functioning. I had hoped the ext3
> support meant I could build the kernel with ext4 only and carry on as
> usual with my ext3 partitions. Unfortunately doing so causes the ext3
> partitions to fail to boot. So...
>
> booting ext3 with ext3 in the kernel=fine
> booting ext4 with ext4 in the kernel=fine
> booting ext3 with ext4 (only) in the kernel=not fine
>
> Is this a problem or was it never intended to work?
It should work...
It'd be more helpful if you could include details on exactly how it
failed, but if Ubuntu builds ext4 as a module, perhaps the initrd
creation sees root as ext3 and doesn't bother to put ext4 in the initrd?
-Eric
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Mounting Ext3 with Ext4
2009-05-21 1:17 ` Eric Sandeen
@ 2009-05-21 1:28 ` Matt LaPlante
2009-05-21 4:37 ` Matt LaPlante
0 siblings, 1 reply; 6+ messages in thread
From: Matt LaPlante @ 2009-05-21 1:28 UTC (permalink / raw)
To: Eric Sandeen; +Cc: linux-ext4
On Wed, May 20, 2009 at 9:17 PM, Eric Sandeen <sandeen@redhat.com> wrote:
> Matt LaPlante wrote:
>> According to the Ext4 howto
>> (http://ext4.wiki.kernel.org/index.php/Ext4_Howto#Converting_an_ext3_filesystem_to_ext4),
>> "It is possible to mount both ext3 (and ext2, in kernels 2.6.28 and
>> later) filesystems directly using the ext4 filesystem driver." So
>> this means, if I'm reading it correctly, that a kernel built with ext4
>> support should be able to mount and manage ext[234] filesystems. Is
>> that correct? If so, are there any limitations on this support?
>>
>> I'm running Ubuntu Jaunty with some custom-built 2.6.29.4 kernels and
>> grub2. I seem to have no problem booting from ext4 disks, so the ext4
>> support is definitely there and functioning. I had hoped the ext3
>> support meant I could build the kernel with ext4 only and carry on as
>> usual with my ext3 partitions. Unfortunately doing so causes the ext3
>> partitions to fail to boot. So...
>>
>> booting ext3 with ext3 in the kernel=fine
>> booting ext4 with ext4 in the kernel=fine
>> booting ext3 with ext4 (only) in the kernel=not fine
>>
>> Is this a problem or was it never intended to work?
>
> It should work...
>
> It'd be more helpful if you could include details on exactly how it
> failed, but if Ubuntu builds ext4 as a module, perhaps the initrd
> creation sees root as ext3 and doesn't bother to put ext4 in the initrd?
ext4 was compiled in directly, it was not a module (this wasn't an
ubuntu kernel; it was stock). I can try to get a stack trace with
netconsole if it gets far enough to function.
>
> -Eric
>
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Mounting Ext3 with Ext4
2009-05-21 1:28 ` Matt LaPlante
@ 2009-05-21 4:37 ` Matt LaPlante
2009-05-21 4:53 ` Eric Sandeen
2009-05-21 5:01 ` Andreas Dilger
0 siblings, 2 replies; 6+ messages in thread
From: Matt LaPlante @ 2009-05-21 4:37 UTC (permalink / raw)
To: Eric Sandeen; +Cc: linux-ext4
On Wed, May 20, 2009 at 9:28 PM, Matt LaPlante <cybrmatt@gmail.com> wrote:
> On Wed, May 20, 2009 at 9:17 PM, Eric Sandeen <sandeen@redhat.com> wrote:
>> Matt LaPlante wrote:
>>> According to the Ext4 howto
>>> (http://ext4.wiki.kernel.org/index.php/Ext4_Howto#Converting_an_ext3_filesystem_to_ext4),
>>> "It is possible to mount both ext3 (and ext2, in kernels 2.6.28 and
>>> later) filesystems directly using the ext4 filesystem driver." So
>>> this means, if I'm reading it correctly, that a kernel built with ext4
>>> support should be able to mount and manage ext[234] filesystems. Is
>>> that correct? If so, are there any limitations on this support?
>>>
>>> I'm running Ubuntu Jaunty with some custom-built 2.6.29.4 kernels and
>>> grub2. I seem to have no problem booting from ext4 disks, so the ext4
>>> support is definitely there and functioning. I had hoped the ext3
>>> support meant I could build the kernel with ext4 only and carry on as
>>> usual with my ext3 partitions. Unfortunately doing so causes the ext3
>>> partitions to fail to boot. So...
>>>
>>> booting ext3 with ext3 in the kernel=fine
>>> booting ext4 with ext4 in the kernel=fine
>>> booting ext3 with ext4 (only) in the kernel=not fine
>>>
>>> Is this a problem or was it never intended to work?
>>
>> It should work...
>>
>> It'd be more helpful if you could include details on exactly how it
>> failed, but if Ubuntu builds ext4 as a module, perhaps the initrd
>> creation sees root as ext3 and doesn't bother to put ext4 in the initrd?
>
> ext4 was compiled in directly, it was not a module (this wasn't an
> ubuntu kernel; it was stock). I can try to get a stack trace with
> netconsole if it gets far enough to function.
It looks likes the magic touch was to add rootfstype=ext4 to the
kernel command line. Prior to this the ext4 only kernel wasn't
finding the disk, but with it attached it now appears to boot
successfully. Maybe worth adding a note to the wiki?
>
>>
>> -Eric
>>
>
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Mounting Ext3 with Ext4
2009-05-21 4:37 ` Matt LaPlante
@ 2009-05-21 4:53 ` Eric Sandeen
2009-05-21 5:01 ` Andreas Dilger
1 sibling, 0 replies; 6+ messages in thread
From: Eric Sandeen @ 2009-05-21 4:53 UTC (permalink / raw)
To: Matt LaPlante; +Cc: linux-ext4
Matt LaPlante wrote:
> It looks likes the magic touch was to add rootfstype=ext4 to the
> kernel command line. Prior to this the ext4 only kernel wasn't
> finding the disk, but with it attached it now appears to boot
> successfully. Maybe worth adding a note to the wiki?
Ah, that makes sense. Sure, please do add it. :)
-Eric
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Mounting Ext3 with Ext4
2009-05-21 4:37 ` Matt LaPlante
2009-05-21 4:53 ` Eric Sandeen
@ 2009-05-21 5:01 ` Andreas Dilger
1 sibling, 0 replies; 6+ messages in thread
From: Andreas Dilger @ 2009-05-21 5:01 UTC (permalink / raw)
To: Matt LaPlante; +Cc: Eric Sandeen, linux-ext4
On May 21, 2009 00:37 -0400, Matt LaPlante wrote:
> It looks likes the magic touch was to add rootfstype=ext4 to the
> kernel command line. Prior to this the ext4 only kernel wasn't
> finding the disk, but with it attached it now appears to boot
> successfully. Maybe worth adding a note to the wiki?
This means that your initrd has "ext3" as the root filesystem type
in /etc/fstab or similar. If the filesystem type is explicitly
given as "ext3" then the ext4 driver will not try to mount it.
I suppose it might be reasonable to have a config option that adds
the "ext3" and "ext2" filesystem types to the ext4 driver for cases
like this where CONFIG_EXT2 and CONFIG_EXT3 (and module equivalents)
are disabled.
Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2009-05-21 5:01 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2009-05-20 23:24 Mounting Ext3 with Ext4 Matt LaPlante
2009-05-21 1:17 ` Eric Sandeen
2009-05-21 1:28 ` Matt LaPlante
2009-05-21 4:37 ` Matt LaPlante
2009-05-21 4:53 ` Eric Sandeen
2009-05-21 5:01 ` Andreas Dilger
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