From: Ted Ts'o <tytso@mit.edu>
To: "Kasatkin, Dmitry" <dmitry.kasatkin@intel.com>
Cc: linux-fsdevel@vger.kernel.org
Subject: Re: Ext4 data structures integrity
Date: Wed, 28 Sep 2011 09:56:26 -0400 [thread overview]
Message-ID: <20110928135626.GA19032@thunk.org> (raw)
In-Reply-To: <CALLzPKb2m6KN7-Weeq4wjUx1RbKutJcnY870tu-hziPvDJkrWQ@mail.gmail.com>
On Wed, Sep 28, 2011 at 04:42:22PM +0300, Kasatkin, Dmitry wrote:
> Hello,
>
> I have a question about Ext4 data structure integrity.
>
> On Ext3 file system I was able to modify offline inode block mapping
> in such a way,
> that 2 inodes did point to the same data blocks, so when modifying one
> file, did affect another file..
> FSCK detects such problems and create duplicated blocks, so that inode
> content will not overlap...
>
> Does Ext4 suffers from the same problem?
That's not a problem that's a feature!
It's REALLY REALLY BAD to try to corrupt the file system the way you
are doing. If you at some point delete one of the files, then that
block will be marked free, and will get reused for something else,
which will then result in all sorts of data consistency problems.
Worse yet, if the block gets reused as a directory block, and then you
modify the remaining file, you could end up corrupting the file system
itself, leading to the loss of access many, many files.
Since ext4 uses the same file system consistency checker as ext3, it
will also find this sort of file system CORRUPTION, and correct it by
duplicating the blocks.
Why in the world would you want to do such a crazy thing in the first
place?
- Ted
next prev parent reply other threads:[~2011-09-28 13:56 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-28 13:42 Ext4 data structures integrity Kasatkin, Dmitry
2011-09-28 13:56 ` Ted Ts'o [this message]
2011-09-28 15:19 ` Kasatkin, Dmitry
2011-09-28 15:45 ` Ted Ts'o
2011-09-29 12:24 ` Kasatkin, Dmitry
2011-09-29 12:56 ` Ted Ts'o
2011-09-29 13:32 ` Kasatkin, Dmitry
2011-09-28 17:16 ` Andreas Dilger
2011-09-29 12:31 ` Kasatkin, Dmitry
2011-09-29 13:33 ` Kasatkin, Dmitry
2011-09-29 13:55 ` Ted Ts'o
2011-10-07 11:40 ` Kasatkin, Dmitry
[not found] ` <64BEDF63-5861-47C9-AC90-F41768D09F17@mit.edu>
2011-10-07 14:20 ` Kasatkin, Dmitry
2011-10-07 15:22 ` Theodore Tso
2011-11-08 23:44 ` Mimi Zohar
2011-11-10 11:21 ` Kasatkin, Dmitry
2011-09-29 16:35 ` Andreas Dilger
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