From: Chris Mason <mason@suse.com>

When filling holes via DIRECT_IO, we fall back to normal buffered io.  For
this to work properly, the direct io funcs have to return a value of zero to
the file write functions, so the file write functions know where to start
writing. 

In some cases, dio->result was getting returned by direct_io_worker, and that
wasn't always zero, causing some data not to be written.

From: <akpm@osdl.org>:

- Simplify things by setting `ret' later on, fix up subsequent damage to the
  dio_complete() args.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>