Subject: Re: bug#18019: bug-parted Digest, Vol 140, Issue 9

From: Phillip Susi <[email-masked]>
Date: Wed, 16 Jul 2014 20:45:09 -0400

On 07/14/2014 03:28 PM, Brian C. Lane wrote:
> The compelling reason for the change, other than just following
> mdadm's suggestion is Doug's example scenario from the bz entry:
> 
> "It's possible, although it means you have a broken setup, that
> you could have a version 1.1 or 1.2 superblock and a version 0.90
> on the same device, and kernel autodetect could assemble it as a
> version 0.90 device and corrupt the real device.  Likewise, if you
> use 0x83, then the kernel filesystem and udev filesystem detection
> code might find something you don't want found."

If you are using 1.1 or 1.2, then the filesystem won't be detected
anyhow since it does not start at sector zero.  Udev scripts also pay
no attention to the partition type code, and so if they were broken
enough to detect the fs and not the 1.0 superblock, they would do so
no matter what the partition type is, so 0xDA doesn't help you there.
 Finally a broken setup with both superblocks present would face the
same problem when mdadm goes to assemble the device instead of the
kernel auto assembler.