Second Block on Partition overwritten with 0xFF

Tomas Pospisek's Mailing Lists tpo2 at
Fri Sep 7 08:46:56 UTC 2007

On Thu, 6 Sep 2007, Andreas Dilger wrote:

> On Sep 06, 2007  23:02 +0200, Tomas Pospisek's Mailing Lists wrote:
>> On Thu, 6 Sep 2007, Christian Kujau wrote:
>>> On Thu, 6 Sep 2007, Tomas Pospisek ML wrote:
>>>> default) at 0x400. Thus as I understand it, it *would* be possible for
>>>> the ext3 driver to pysically write to those first sectors inside its
>>>> partition.                                                ^^^^^^
>>> Yes, ext3 will write *inside* its assigned partition, but not outside.
>> Thanks, however it seems I can not get through what I need to know -
>> sorry for that. I *do* know that ext3 will only write to its partition
>> only. But once mke2fs has run:
>> * will ext2/3 *ever* write to the first 4 sectors on *its* partition?
>> Same question restated: is it possible that ext2/3 will write into the
>> space before the first block group [1]?
> The ext2/3/4 superblock is at offset 1024 bytes.  It is written by marking
> the buffer it is in dirty.  If the filesystem blocksize is > 1024 bytes
> then the whole block will be written to disk (including the first sectors).
> That said, the buffer cache is coherent when written by the filesystem and
> when written via /dev/XXX so any modifications made to the first sectors
> should be rewritten each time the superblock is marked dirty.  The ext3
> code will never itself modify those sectors.


   Tomas Pospisek -  Linux & Open Source Solutions

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