On Mon, Jan 05, 2009 at 05:16:08PM +0900, Toshiyuki Okajima wrote:

I was confirming whether the kernel to which your new patch is
applied can run without trouble. But unfortunately, I got a hangup
problem. Now I am investigating the root cause.  After I
investigated it for a little time, I think calling log_wait_commit()
from journal_try_to_free_buffers() can cause it.  

Sounds like a deadlock caused by the fact that we're no longer masking
__GFP_WAIT, probably on journal->j_wait_done_commit.  Presumably the
system came under pressure during a commit operation, which makes
sense, and so we ended up with a deadlock between kjournald and
kswapd.  The fix is pretty simple; we just need to mask out the
__GFP_WAIT in the filesystem-specific callback, since this is a
restriction imposed by the filesystem's use of the jbd/jbd2 layer.

	    	       	   		       - Ted