linux-ext4 - Re: flashing large eMMC partitions with ext4

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Date:	Wed, 3 Aug 2011 01:07:08 +0900 (JST)
From:	Round Robinjp <roundrobinjp@...oo.co.jp>
To:	Goldstein Amir <amir73il@...il.com>
Cc:	Andreas Dilger <aedilger@...il.com>, Ted Ts'o <tytso@....edu>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: flashing large eMMC partitions with ext4

Amir

> > But after extending to 4G, e2fsck makes some complain.
> > I guess this is not expected behaviour, is it?
> >
> 
> it is expected when you use the current resize2fs,
> which does not respect the flex_bg layout, so new group block bitmaps
> are allocated beyond the 1G border and initialized.

So that means I have thrown away some important part of
the filesystem when I did truncate -s 1G, isn't it?
Will things go wrong if I flash this 1G image to my eMMC
partition (without using Yongqiang's new 64bit resize patches)?
I need to understand whether Yongqiang's patch is absolutely
necessary for this purpose or just a good thing to have.

> if you use Yongqiang's new 64bit resize patches, the final fsck won't complain.
> unfortunately for you, those patches have not been merged to the kernel yet,
> so you will have to either build your own ext4 module or wait at least until
> kernel 3.2 is released to have it in mainline.

As said above.

> It is actually quite simple to fix the 1G image, so it will pass fsck
> after truncate -s 4G.
> All it takes it setting the BLOCK_UNINIT flag in groups 8-31
> this should be possible to do with debugfs (or write a small tool to do it).
> if I have time, it will try it myself and post the instructions.

OK, thanks in advance.

Best Regards
Round
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