Thread (2 messages) 2 messages, 1 author, 2011-01-21

Re: [BUG] ext3/ext4 migration problem with dir_nlink feature flag

From: Akira Fujita <hidden>
Date: 2011-01-21 07:34:46

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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