Re: [GIT PULL] Ext3 removal, quota & udf fixes

[Jeff Mahoney]

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On 9/1/15 8:52 AM, Eric Sandeen wrote:
> On 8/31/15 5:39 PM, Linus Torvalds wrote:
>> On Mon, Aug 31, 2015 at 3:31 PM, Raymond Jennings
>> <shentino@xxxxxxxxx> wrote:
>>> 
>>> That said, I wouldn't mind myself if the ext4 driver were given
>>> a very grueling regression test to make sure it can actually
>>> handle old ext3 systems as well as the ext3 driver can.
>> 
>> That's not my only worry. Things like "can you go back to
>> ext3-only" is an issue too - I don't think that's been a big
>> priority for ext4 any more, and if there are any existing
>> hold-outs that still use ext3, they may want to be able to go
>> back to old kernels.
> 
> Others have said it as well, but I'll restate: Yes, you can go
> "back."
> 
> But there's no real "going back" needed, because mounting an ext3 
> filesystem with ext4.ko hasn't "gone anywhere."  If you use
> ext4.ko, you are running with a newer driver, but not a newer disk
> format.
> 
>> So it's not just a "you can use ext4 instead" issue. Can you do
>> that *without* then forcing an upgrade forever on that partition?
>> I'm not sure the ext4 people are really even willing to guarantee
>> that kind of backwards compatibility.
> 
> Yeah, we are, I think I remember making an explicit stink about
> that quite a while ago.  But I'm satisfied; we do use
> CONFIG_EXT4_USE_FOR_EXT23 in RHEL7, and we wouldn't do that if it
> might change disk format behind our users' backs.

As a "me too" datapoint, we do the same thing with SLE12.

- -Jeff

- -- 
Jeff Mahoney
SUSE Labs
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