Bug#615998: linux-image-2.6.32-5-xen-amd64: Repeatable "kernel BUG at fs/jbd2/commit.c:534" from Postfix on ext4

["Moffett, Kyle D" <Kyle.D.Moffett@boeing.com>]

On Jun 23, 2011, at 16:55, Sean Ryle wrote:
> Maybe I am wrong here, but shouldn't the cast be to (unsigned long) or to (sector_t)?
> 
> Line 534 of commit.c:
>                         jbd_debug(4, "JBD: got buffer %llu (%p)\n",
>                                 (unsigned long long)bh->b_blocknr, bh->b_data);

No, that printk() is fine, the format string says "%llu" so the cast is
unsigned long long.

Besides which, line 534 in the Debian 2.6.32 kernel I am using is this
one:

  J_ASSERT(commit_transaction->t_nr_buffers <=
           commit_transaction->t_outstanding_credits);

If somebody can tell me what information would help to debug this I'd be
more than happy to throw a whole bunch of debug printks under that error
condition and try to trigger the crash with that.

Alternatively I could remove that J_ASSERT() and instead add some debug
further down around the "commit_transaction->t_outstanding_credits--;"
to try to see exactly what IO it's handling when it runs out of credits.

Any ideas?

Cheers,
Kyle Moffett