3.14-rc2 XFS backtrace because irqs_disabled.

[Dave Jones]

On Wed, Feb 12, 2014 at 04:40:43PM +1100, Dave Chinner wrote:

 > None of the XFS code disables interrupts in that path, not does is
 > call outside XFS except to dispatch IO. The stack is pretty deep at
 > this point and I know that the standard (non stacked) IO stack can
 > consume >3kb of stack space when it gets down to having to do memory
 > reclaim during GFP_NOIO allocation at the lowest level of SCSI
 > drivers. Stack overruns typically show up with symptoms like we are
 > seeing.
 > ..
 > 
 > Dave, before chasing ghosts, can you (like Eric originally asked)
 > turn on stack overrun detection?

CONFIG_DEBUG_STACKOVERFLOW ? Already turned on.

	Dave