Location of backup superblocks

[Felipe Monteiro de Carvalho <felipemonteiro.carvalho@xxxxxxxxx>]

Hello,

I am trying to recover a XFS partition (or series of partitions) where
the main superblock was corrupted, and I see that there are multiple
superblock copies. I'd like to guess the partition start and size
also.

I see that the partition size can be calculated with sb_blocksize* sb_dblocks

But what about the partition start? I think I can guess it based in
the position of the found superblocks.

Any ideas where is the code that writes to disk those backup
superblocks? So far to me it looks like that their position is
calculated as disk_size / 4 rounded (nearest rounding?) to a multiple
of sb_blocksize, but having the exact code part would be better of
course =) Or even better, a list of backup superblock positions...

thanks,
-- 
Felipe Monteiro de Carvalho