Re: [PATCH 1/5] jbd: Fail to load a journal if it is too short

[Andreas Dilger <adilger@sun.com>]

On Jul 21, 2009  09:19 -0700, Andrew Morton wrote:
> On Tue, 21 Jul 2009 12:04:15 +0200 Jan Kara <jack@suse.cz> wrote:
> > Due to on disk corruption, it can happen that journal is too short. Fail
> > to load it in such case so that we don't oops somewhere later.
> > 
> > Reported-by: Nageswara R Sastry <rnsastry@linux.vnet.ibm.com>
> > Signed-off-by: Jan Kara <jack@suse.cz>
> > ---
> >  fs/jbd/journal.c |    6 ++++++
> >  1 files changed, 6 insertions(+), 0 deletions(-)
> > 
> > diff --git a/fs/jbd/journal.c b/fs/jbd/journal.c
> > index 737f724..94a64a1 100644
> > --- a/fs/jbd/journal.c
> > +++ b/fs/jbd/journal.c
> > @@ -848,6 +848,12 @@ static int journal_reset(journal_t *journal)
> >  
> >  	first = be32_to_cpu(sb->s_first);
> >  	last = be32_to_cpu(sb->s_maxlen);
> > +	if (first + JFS_MIN_JOURNAL_BLOCKS > last + 1) {
> > +		printk(KERN_ERR "JBD: Journal too short (blocks %lu-%lu).\n",
> > +		       first, last);
> > +		journal_fail_superblock(journal);
> > +		return -EINVAL;
> > +	}
> >  
> >  	journal->j_first = first;
> >  	journal->j_last = last;
> 
> It's odd that sb->s_first/s_maxlen are 32-bit and
> journal->j_first/j_last are unsigned long.
> 
> These things will only ever be 32-bit unless we change the journal
> superblock.

The jbd on disk structure and APIs cannot handle 64-bit block numbers.
That is one of the first changes we made for jbd2 so that it is possible
to store either 32-bit or 64-bit block numbers in a transaction.  I don't
think that needs to be fixed for the jbd code.

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.