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Date:	Wed, 2 Sep 2015 00:30:39 -0300
From:	Albino B Neto <>
To:	Austin S Hemmelgarn <>
Cc:	Raymond Jennings <>,
	Linus Torvalds <>,
	Jan Kara <>, LKML <>,
	"" <>,
	linux-fsdevel <>
Subject: Re: [GIT PULL] Ext3 removal, quota & udf fixes

2015-08-31 23:53 GMT-03:00 Theodore Ts'o <>:
> Yes, you can go back to ext3-only.  In fact, we do *not* automatically
> upgrade the file system to use ext4-specific features.
>> 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.
> Actually, we do guarantee this.  It's considered poor form to
> automatically change the superblock to add new file system features in
> a way that would break the ability for the user to roll back to an
> older kernel.  This isn't just for ext3->ext4, but for new ext4
> features such as metadata checksumming.  The user has to explicitly
> enable the feature using "tune2fs -O new_feature /dev/sdXX".


2015-09-01 16:39 GMT-03:00 Austin S Hemmelgarn <>:
> NO, it is not logical.  A vast majority of Android smartphones in the wild
> use ext2, as do a very significant portion of embedded systems that don't
> have room for the few hundred kilobytes of extra code that the ext4 driver
> has in comparison to ext2.

Ext2 portion embedded and Ext3 many machines.

Albino B Neto
"Debian. Freedom to code. Code to freedom!" faw
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