linux-ext4 - Re: E2fsprogs master branch now has all 64-bit patch applied

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Message-Id: <B76CA57A-4379-494C-8DC6-DE041F2A4555@dilger.ca>
Date:	Fri, 25 Jun 2010 12:23:48 -0600
From:	Andreas Dilger <adilger@...ger.ca>
To:	Hsuan-Ting <acht93@...ccu.edu.tw>
Cc:	tytso@....edu,
	"linux-ext4@...r.kernel.org development" <linux-ext4@...r.kernel.org>
Subject: Re: E2fsprogs master branch now has all 64-bit patch applied

On 2010-06-25, at 04:33, Hsuan-Ting wrote:
> My test case:
> 1. build a linear raid (1 x 2TB disk)
> 2. mkfs.ext4, mount it and"echo 123 > test" to
> touch a test file.
> 3.  grown the linear raid to >16TB (9 x 2TB + 1 x 1.5TB)
> 4. do resize ( resize -fpF /dev/md2 )
> After resizing, the content of the test file is correct.

This is mostly unsurprising, since there is very little chance that the single file is corrupted by a resize.  Better would be to fill nearly the whole filesystem (e.g. llverfs, previously posted to this list) and verify the file contents after the resize.

> But "fsck -nyv" will get the following error:
> I think maybe I should modify "ext2_ino_t" type from
> "__u32" to "__u64".
> Maybe this modification will fix many overflow issue.

No, this will completely break the ext2/3/4 on-disk format.  What you need to make sure is that when resize2fs is resizing the filesystem that it limits the total number of inodes in the filesystem to 2^32-1.  I guess that means the groups beyond the 2^32nd inode will have no inode table at all, which is a bit strange, but something that we need to expect in e2fsck.

I guess the alternative would be to allocate the inode table, but we couldn't (yet?) use those inodes without significant work to support 64-bit inode numbers.  Probably the first step in that direction would be the "dirdata" patch that we have to allow storing extra data in directory entries.

Cheers, Andreas

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