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Re: another seriously corrupt ext3 -- pesky journal



On Thu, Aug 21, 2003 at 03:28:03PM -0400, Erez Zadok wrote:
> How does the kernel know to write the journal data first to some data block
> belonging to inode X, and then to another data block of inode Y?  Both X and
> Y are journal inodes, right?  Will there be a reserved inum other than 8,
> for the backup journal?
> 
> Is there some magic in which the kernel can identify any number of special
> journal inodes?
> 
> And while we're at it, why only one backup journal inode?  Why not several?
> If it's good enough to have several copies of superblocks etc., then why not
> the journal (for those willing to pay the performance penalty)?

Erez,

If I understand Ted correctly, the contents of the journal inode, not the
contents of the journal, are replicated.  In particular, there is a copy
of the block pointers that specify where the journal is located.  The JBD
code takes care of ensuring that the data in the journal is not garbage.
The problem is when the journal block pointers (i.e., the journal meta-data)
that identify where the journal lives (since it is just a file, identified
by a list of block pointers) get corrupted.

Regards,

	Bill Rugolsky




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