Hi,

On Thu, Nov 15, 2001 at 04:21:49PM -0700, Andreas Dilger wrote:

> I don't disagree that something corrupted it, but it is hard to tell from
> here what it could be.  Looking at ext3_read_super(), it is pretty much
> a read-only path, except journal recovery.  If, for some reason, you had
> an old, unrecovered ext3 journal in the fs, it is possible that recovering
> from it would corrupt your fs by writing old data into the fs.

Except that can only happen once we have found a journal to recover,
and the error that ext3 spat out indicated that it couldn't find a
journal at all and was giving up.

> Looking at the ext3_read_super() path, we call ext3_load_journal(),
> which calls journal_wipe() and journal_load(), which both call
> journal_load()->load_superblock()->journal_get_superblock(), which
> gives us the two "JBD: no valid journal superblock found" messages,
> and return errors before doing anything else.  Then we get the message
> "EXT3-fs: error loading journal." and return without mounting the fs.

Indeed.

> Hmm, there is a possibility that journal_destroy() calling
> journal_update_superblock() scribbling data into the first block of
> the old "journal".  Stephen, Andrew, we need to exit from the
> journal_get_superblock() with j_sb_buffer = NULL, and then check for
> this in journal_destroy() so we don't call journal_update_superblock().
> How does the below patch look?

Looks OK.  I've done a slightly better version which catches a couple
of extra cases but it's basically the same solution.  I've also added
a tiny patch to prevent a failed journal_wipe() from being followed by
a journal_load() attempt, so we don't get the same error twice.

Patch below.

Cheers,
 Stephen