On Wed, Feb 03, 2016 at 07:40:15PM +0100, Christoph Hellwig wrote:

We only need to communicate two bits of information to the direct I/O
completion handler:

 (1) do we need to convert any unwritten extents in the range
 (2) do we need to check if we need to update the inode size based
     on the range passed to the completion handler

We can use the private data passed to the get_block handler and the
completion handler as a simple bitmask to communicate this information
instead of the current complicated infrastructure reusing the ioends
from the buffer I/O path, and thus avoiding a memory allocation and
a context switch for any non-trivial direct write.  As a nice side
effect we also decouple the direct I/O path implementation from that
of the buffered I/O path.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <redacted>

This change is now dependent on the preceeding direct IO API
changes. Do I a) take the DIO API change through the XFS tree, or
b) use the older version of the patch that didn't have this
dependency and let somebody else deal with the API change and merge
issues?

I'm happy to take the DIO API change through the XFS tree, if that's
the fastest/easiest way to get the necessary DIO subsystem fixes
into the mainline tree for XFS. As such, the for-next tree that I'm
building right now will include the DIO API change patch....

-Dave.

-- 
Dave Chinner
david@fromorbit.com