linux-ext4 - Re: [BUG] ext3/ext4 migration problem with dir

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Date:	Fri, 21 Jan 2011 16:34:24 +0900
From:	Akira Fujita <a-fujita@...jp.nec.com>
To:	Theodore Tso <tytso@....edu>,
	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: [BUG] ext3/ext4 migration problem with dir_nlink feature flag

Hi,

Unfortunately, this bug still exists in 2.6.38-rc1 with e2fsprogs-1.41.13.
Attached test program can reproduce this bug easily.
Please have a look and try.

Regards,
Akira Fujita

(2010/10/06 11:44), Akira Fujita wrote:
> Hi,
> 
> I found a bug which returns EIO by file access on ext3 (was ext4) whose
> dir_nlink feature flag is removed and has more than 64000 directories.
> Kernel: 2.6.36-rc6, e2fsprogs: 1.41.2
> Steps to reproduce are as follows:
> 
> 1. Create ext4 which does not have extent and flex_bg feature flags
> (Because this fs will be mounted as ext3 in step 3),
> then create more than 64000 directories.
> Therefore dir_nlink feature flag is set and link count becomes 1.
> 2. Remove dir_nlink feature flag with tune2fs command
> (e.g. tune2fs -O ^dir_nlink /dev/sdx).
> 3. Mount ext4 as ext3, then remove subdir (Link: 1->0).
> We cannot access parent directory, because link count goes wrong.
> 
> We should disallow tune2fs command to remove dir_nlink feature flag.
> 
> Regards,
> Akira Fujita
> 
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Download attachment "dir_nlink.sh" of type "application/x-shellscript" (1313 bytes)