There's a problem with the REQ_BLOCK_PC handling as well (bad ->data_len
handling) where it could actually complete a request ahead of time.  I
suggest we just back this out for now, I will resubmit it later when I'm
fully confident in it.

This reverts commit 8672d571

Signed-off-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>