linux-kernel - Re: [RFC][9/11][MANUX] Kernel compatibility : ext2's dtime field?

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Message-ID: <20140415201026.GJ4456@thunk.org>
Date:	Tue, 15 Apr 2014 16:10:26 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Emmanuel Colbus <ecolbus@...ux.info>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [RFC][9/11][MANUX] Kernel compatibility : ext2's dtime field?

On Tue, Apr 15, 2014 at 03:43:12PM +0200, Emmanuel Colbus wrote:
> Now, another question. In ext2, what is the point of the dtime field?
> Personaly, I'm never setting it, because, well, if an inode is removed,
> it's removed, and nobody is supposed to access it again; and anyways,
> since no syscall allows seeing it, the dtime seems to me like nothing
> but an information leakage. But I doubt you would have put a useless
> data in the filesystem, so I'm likely overlooking something; if so, what
> is it?

For ext2, it was useful as a way of being able to do some emergency
undelete operations on a file system.  These days, it's mostly for
debugging purposes.

This field is also used as a linked list in ext3 and ext4 for "orphan
inodes" and inodes which are in the process of being truncated or for
which should be truncated after a crash (to avoid leaking stale data,
for example).

						- Ted
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