Re: Btrfs: wipe all the superblock [redhat bugzilla 889888]

[Goffredo Baroncelli <kreijack@gmail.com>]

Hi Karel,

> 
>  You can specify more than one magic strings for the same filesystem,
>  the .magics = { } is array.

thanks for you suggestion. However this seems to me not applicable. I
tried to change the code, and what I got to me seems inconsistently:

Whit this change

1) if I do "wipefs <device>", I got the offset of the first superblock
(good enough)
2) if I do "wipefs -a <device>", I clean-up *all three* superblocks
(very good)
3) if I do "wipefs -o <offset> <device>", I clean-up only the superblock
located at <offset> (very bad)

If the user doesn't know enough btrfs, trying 1) and 3) could think that
the disk is cleaned-up. Instead the 2nd and the 3rd super-blocks still
exist.

>  see for example libblkid/src/superblocks/reiserfs.c 

I think that this is a different case: the reiser superblocks are
*alternative*; instead in the btrfs case, *all the three superblocks*
exist at the same time.

>  Karel
Ciao
Goffredo

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