linux-ext4 - Re: ext34_free

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Date:	Wed, 14 Apr 2010 11:03:50 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Jan Kara <jack@...e.cz>
CC:	Dmitry Monakhov <dmonakhov@...nvz.org>,
	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: ext34_free_inode's mess

Jan Kara wrote:
> On Wed 14-04-10 15:19:47, Dmitry Monakhov wrote:
>> I've finally automated my favorite testcase (see attachment), 
>> before i've run it by hand.
>> And sometimes i've saw following complain from fsck:
>> fsck.ext4 -f -n /dev/sdb2
>> ...
>> Pass 5: Checking group summary information
>> Inode bitmap differences:  -93582
>> Fix? no
>>
>> Free inodes count wrong for group #12 (4634, counted=4633).
>> Fix? no
>>
>> Free inodes count wrong (35610, counted=35609).
>> Fix? no
>> ...
>   Interesting. So some inode is marked as free although it is in
> use, right? That sounds like a nasty bug - if you reproduce this
> again, could you use debugfs to find out what file type is that
> inode? It could help looking for the bug.

running fsstress in verbose mode, and disabling link/unlink/symlink,
you can sometimes narrow it down to a sequence of operations on that file, too.
(keep track of the seed nr...)

Of course if it's a random-ish race that probably won't be of much use.  :)

-Eric
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