linux-ext4 - Re: question about i_dtime being used as an orphan list pointer

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Date:	Wed, 25 Aug 2010 16:39:14 -0400
From:	Ted Ts'o <tytso@....edu>
To:	Vitali Lovich <vlovich@...il.com>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: question about i_dtime being used as an orphan list pointer

On Wed, Aug 25, 2010 at 12:22:22PM -0700, Vitali Lovich wrote:
> So I've run into this problem where the clock was reset into the 1970s
> on my system, causing e2fsck to get confused & think a file I deleted
> actually had an orphan list inode pointer stored in the i_dtime
> instead of the deletion time, causing e2fsck to get all confused &
> return an error code.

Are you worried about solving this problem as a one shot deal, or as a
long-term design issue.  The long-term proper solution is run your
clock so it is correct.  :-)

In the short term, probably the easist thing to do is just run e2fsck
-y and let those inodes get populated into lost+found, and then delete
them by hands afterwards.

For a long-term fix, it probably would make sense to patch ext3/ext4
so that when we delete a file, and the current time is less than
number of inodes, that we set dtime to 0xffffffff.

> Even a value of midnight 2010 corresponds to a limit of only about 1
> billion files (1 262 304 000).  Thus it seems if you delete a file on
> a partition with more than a billion files, it will make e2fsck think
> you've got a corrupt file-system even though you don't.

And if you assuming the smallest possible inode ratio, that's a 4.5TB
file.  If you use the default inode, that's a 18TB.  Ext3 is limited
to 16TB, so that's not even an issue....

	   	    				- Ted
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