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

On Tue 30-08-11 19:26:22, Moffett, Kyle D wrote:

On Aug 30, 2011, at 18:12, Jan Kara wrote:

quoted

quoted

I can still trigger it on my VM snapshot very easily, so if you have anything
you think I should test I would be very happy to give it a shot.

 OK, so in the meantime I found a bug in data=journal code which could be
related to your problem. It is fixed by commit
2d859db3e4a82a365572592d57624a5f996ed0ec which is in 3.1-rc1. Have you
tried that or newer kernel as well?

If the problem still is not fixed, I can provide some debugging patch to
you. We spoke with Josef Bacik how errors like yours could happen so I have
some places to watch...

I have not tried anything more recent; I'm actually a bit reluctant to move
away from the Debian squeeze official kernels since I do need the security
updates.

I took a quick look and I can't find that function in 2.6.32, so I assume it
would be a rather nontrivial back-port.  It looks like the relevant code
used to be in ext4_clear_inode somewhere?

  It's not that hard - untested patch attached.

Out of curiosity, what would happen in data=journal mode if you unlinked a
file which still had buffers pending?  That case does not seem to be handled
by that commit you mentioned, was it already handled elsewhere?

  Once the file is deleted, it's OK to discard its data after a
transaction doing delete commits. The current code in JBD2 handles this
case fine - the problem was that for not-deleted files we cannot discard
dirty data after a transaction commits ;)

								Honza
-- 
Jan Kara [off-list ref]
SUSE Labs, CR