linux-ext4 - Re: [PATCH e2fsprogs] Add ZFS detection to libblkid

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Date:	Sat, 04 Apr 2009 08:04:17 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	"Ricardo M. Correia" <Ricardo.M.Correia@....COM>
CC:	"Theodore Ts'o" <tytso@....edu>, linux-ext4@...r.kernel.org,
	Andreas Dilger <adilger@....COM>
Subject: Re: [PATCH e2fsprogs] Add ZFS detection to libblkid

Eric Sandeen wrote:
> Ricardo M. Correia wrote:
>> This patch adds ZFS filesystem detection to libblkid.
>>
>> It probes for VDEV_BOOT_MAGIC in the first 2 ZFS labels in big-endian
>> and little-endian formats.
>> Unfortunately the probe table doesn't support probing from the end of
>> the device, otherwise we could also probe in the 3rd and 4th labels (in
>> case the first 2 labels were accidentally overwritten)..
>>
>> Eventually we would set the UUID from the ZFS pool GUID and the LABEL tag
>> from the pool name, but that requires parsing an XDR encoding of the pool
>> configuration which is not trivial.
> 
> Hi Ricardo:
> 
> I've got a bug on fedora now where a partition w/ zfs on it is being
> recognized as ext3.  VDEV_BOOT_MAGIC isn't anywhere in the first 1M of
> the device, though an old ext3 superblock is intact.  :(
> 
> # hexdump -C sda2-first-1M | grep "0c b1 07 b0 f5 02 00 00"
> # hexdump -C sda2-first-1M | grep "00 00 02 f5 b0 07 b1 0c"
> #
> 
> (so a plea - can you guys change mkfs to zero old signatures?  maybe
> 256k at the front & end of the device in question?)
> 
> there is apparently an uberblock signature in it though:
> 
> # hexdump -C sda2-first-1M | grep "0c b1 ba 00"
> 00015e30  30 e8 ff ff 85 c0 5b 75  48 8b 06 35 0c b1 ba 00
> 
> does blkid need more work here, I guess?

And from another report, another user's zfs partition:

# hexdump -C first_400K | grep "0c b1 07 b0 f5 02 00 00"
# hexdump -C first_400K | grep "00 00 02 f5 b0 07 b1 0c"
# hexdump -C first_400K | grep "0c b1 ba 00"
00015e30  30 e8 ff ff 85 c0 5b 75  48 8b 06 35 0c b1 ba 00

Should we be looking for 0x00babloc at offset 00015e30?

Thanks,
-Eric
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