ext3_direct_io_get_blocks() is misinterpreting the return value from
ext3_journal_extend(), and is consequently running out of buffer credits and
going BUG on tremendously large direct-io writes.  Fix that up.

Also, I note that the really large direct-io writes can hold a transaction
open for the entire duration, which can be minutes.  This violates ext3's
attempt to commit data at regular intervals.  Fix that up by looking at the
transaction state: if it's T_LOCKED, shut off the current handle so the
pending commit can complete.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>