On Tue, 2002-03-26 at 08:34, Steve Lord wrote: > On Mon, 2002-03-25 at 21:50, Derek James Witt wrote: > > Hey all. > > > > I'm going through the kernel source for XFS and I'm trying to find out > > how many superblocks a partition usually has and the maximum it's > > allowed to have. So far in xfs_mount.h, I'm seeing that we are allowed > > two superblocks. I am proposing that we have two consecutive primary > > superblocks (duplicates) in use. In other words, mirrored blocks. > > > > So, if lilo or any other boot loader comes along and overwrites a part > > of the first superblock, the mounting code can still get at the 2nd sb. > > But, the problem is that the size of the superblock I've seen varies > > from 512 bytes to 65535 bytes. In lilo's sources, we got blocks of size > > 1024 and sector sizes of 512. Any ideas on what to do on this? > > > > Nathan answered some structural details here, but the idea of placing > a second super block after the first will not work, the second 512 bytes > of the filesystem contain another data structure. In fact there are > data structures in the first 2K of disk, then a 2K gap, then regular > metadata can start at 4K. > > The only fields in the primary superblock which change are the totals > of free space and inodes used. These can all be reconstructed with xfs > repair. > > Thanks for the lilo patch though. > > Steve > > > -- > > Steve Lord voice: +1-651-683-3511 > Principal Engineer, Filesystem Software email: lord@sgi.com > -- ** Derek J Witt ** * Email: mailto:djw@flinthills.com * * Home Page: http://www.flinthills.com/~djw/ * *** "...and on the eighth day, God met Bill Gates." - Unknown **
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