Excerpts from Josef Bacik's message of 2011-01-19 09:14:02 -0500:

On Wed, Jan 19, 2011 at 10:08:13PM +0800, Liuwenyi wrote:

quoted

In Yang Ruirui's mail, the btrfs will create a oops. This is caused by a
null pointer in test_range_bit() while lock the spinlock.

So, It is necessary to add a pointer check into test_range_bit()

NAK, the tree shouldn't be null coming into this function, something else is
going wrong.  What oops is this?  Thanks,

What was your metadata blocksize for this oops?  This call should never
happen.

I think there is a larger problem, probably in the IO error handling
code since the trace had io errors beforehand.

-chris