Here is a reworked version of my patch to ext3 to retry certain
filesystem operations after an ENOSPC error.  The
ext3_should_retry_alloc() function will not wait on the currently
running transaction if there is a currently active handle; hence this
should avoid deadlocks in the Lustre use case.  The patch is versus
BK-recent.

I've also included a simple, reliable test case which demonstrates the
problem this patch is intended to fix.  (Note that BK-recent is not
sufficient to address this test case, and waiting on the commiting
transaction in ext3_new_block is also not sufficient.  Been there,
tried that, didn't work.  We need to do the full-bore retry from the
top level.  The ext3_should_retry_alloc() will only wait on the
committing transaction if there is an active handle; hence Lustre will
probably also need to use ext3_should_retry_alloc() if it wants to
reliably avoid this particular problem.)

						- Ted